Acessibilidade / Reportar erro

Nitrogen Fertilization of No-Tillage Winter Cereals in the South-Central Region of Paraná, Brazil

ABSTRACT

High winter cereal yields depend on an adequate supply of nitrogen (N). We developed a system for indicating N rates for wheat and barley in the South-Central region of the state of Paraná, Brazil, using results of 72 field experiments conducted from 2007 to 2012. The N rates recommended for winter cereals were estimated to supply the amounts of N fertilizer needed to obtain increasing yields (<3.5, 3.5-4.5, 4.5-5.5, and >5.5 Mg ha-1) of crops grown after soybean and corn on soils with a variable organic matter content (<40, 40-60, and >60 g dm-3). The apparent mineralization rate of soil N was estimated to be 1 % and the N fertilization efficiency 50 %. The N rates recommended for wheat ranged from 30 to 150 kg ha-1 when cultivated after soybean, and from 30 to 170 kg ha-1 after corn. The N rates for barley ranged from 30 to 120 kg ha-1 when grown after soybean, and from 30 to 130 kg ha-1 after corn. These N rates are consistent with those indicated by the Soil Fertility Commission for the states of Rio Grande do Sul and Santa Catarina (CQFS-RS/SC, 2016), and also with the rates of maximum economic efficiency estimated in our study. The proposed N rate recommendation system can be used by agricultural technicians and producers to manage N fertilization of wheat and barley in the South-Central region of Paraná, Brazil.

Triticum aestivum; Hordeum vulgare L.; N indication; urea

INTRODUCTION

Winter cereals grown in rotation with soybean (Glycine max L.) or corn (Zea mays L.) in the South-Central region of Paraná, Brazil, cover an area of approximately 60,000 ha, cultivated exclusively under no-tillage (Fontoura et al., 2015Fontoura SMV, Vieira RCB, Bayer C, Viero F, Anghinoni I, Moraes RP. Fertilidade do solo e seu manejo em sistema plantio direto no centro-sul do Paraná. Guarapuava: Fundação Agrária de Pesquisa Agropecuária; 2015.). Roughly one-half of the acreage produces wheat (Triticum aestivum L.) and the other half barley (Hordeum vulgare L.), with a mean yield of around 5,000 kg ha-1 (Agrária, 2016Agrária. Annual Report [internet]. Guarapuava: Agrária; 2016 [acesso em 17 de novembro 2016]. Disponível em: http://www.agraria.com.br/en/relatorio_anual.php
http://www.agraria.com.br/en/relatorio_a...
). However, grain yield in both crops in experimental areas managed by the Fundação Agrária de Pesquisa Agropecuária (FAPA) in Guarapuava-PR is as high as 9,000 kg ha-1, which testifies to the high productive potential of these cereals in the region and demonstrates a marked yield difference between experimental sites and farmers’ fields.

Grain productivity depends not only on the use of productive varieties, and suitable phytosanitary and weed control measures (Benin et al., 2012Benin G, Bornhofen E, Beche E, Pagliosa ES, Silva CL, Pinnow C. Agronomic performance of wheat cultivars in response to nitrogen fertilization levels. Acta Sci Agron. 2012;34:275-83. https://doi.org/10.4025/actasciagron.v34i3.14468
https://doi.org/10.4025/actasciagron.v34...
), but also on an adequate supply of nutrients (particularly nitrogen N) (De Bona et al., 2016De Bona FD, De Mori C, Wietholter S. Manejo nutricional da cultura do trigo. Piracicaba: IPNI; 2016. (Informações Agronômicas, 154).). However, the lack of recommendation systems to facilitate efficient N fertilization in some Brazilian regions has led to poorer cereal responses to N fertilization and lower profitability relative to other crops such as corn. The N rates recommended for wheat in the states of Mato Grosso do Sul and São Paulo are based on grain yield expectations and the preceding crop (Minella, 2015Minella E. Indicações técnicas para a produção de cevada cervejeira nas safras 2015 e 2016. In: XXX Reunião Nacional de Pesquisa de Cevada; 2015; Passo Fundo. Passo Fundo: Embrapa Trigo; 2015. (Sistemas de Produção 8).). However, in the states of Rio Grande do Sul and Santa Catarina, the estimated N rates also consider the organic matter content, which is related to the potential of the soil to supply the crops with N (CQFS-RS/SC, 2016Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016.).

The South-Central region of Paraná lacks an official N recommendation system for winter cereals. Despite the high technology levels in regional agriculture, the recommended N rates for winter cereals have been based on average N rates established by technicians and producers or on recommendations extrapolated from other regions such as Rio Grande do Sul and Santa Catarina. As with corn (Fontoura and Bayer, 2009Fontoura SMV, Bayer C. Adubação nitrogenada para alto rendimento de milho em plantio direto na região Centro-Sul do Paraná. Rev Bras Cienc Solo. 2009;33:1721-32. https://doi.org/10.1590/S0100-06832009000600021
https://doi.org/10.1590/S0100-0683200900...
), a specific N recommendation system for winter cereals might increase the agronomic efficiency of N fertilizers while minimizing the potential impact of these nutrient inputs on the environment.

In this study, we tested the hypothesis that N rates to be applied aiming to attain crescent grain yields of wheat and barley are also dependent on soil organic matter level and preceding summer crop. Our main objective was to develop an N recommendation system for wheat and barley in the South-Central region of Paraná that considers the preceding crop (soybean or corn), soil organic matter, and expected grain yield by examining the results of 72 field experiments performed from 2007 to 2012 in experimental areas managed by the FAPA.

MATERIAL AND METHODS

Region description

The South-Central region of Paraná is located on the third physiographic plateau of the state (Figure 1), 800 to 1,200 m a.s.l. The soils were derived from basalt and are predominantly Brown Latossol by Brazilian Classification (Fontoura et al., 2015Fontoura SMV, Vieira RCB, Bayer C, Viero F, Anghinoni I, Moraes RP. Fertilidade do solo e seu manejo em sistema plantio direto no centro-sul do Paraná. Guarapuava: Fundação Agrária de Pesquisa Agropecuária; 2015.) and clayey Hapludox (Soil Survey Staff, 2014Soil Survey Staff. Keys to soil taxonomy. 12th ed. Washington, DC: United States Department of Agriculture, Natural Resources Conservation Service; 2014.). With regard to soil organic matter (OM), 59 % of the soils of the region managed by the Cooperativa Agrária Agroindustrial (Guarapuava, Paraná) contain 41-60 g dm-3 of OM, 16 % contain less than 40 g dm-3 of OM, and 25 % more than 60 g dm-3 of OM (Figure 1).

Figure 1
Map of Southern Brazil and South-Central Paraná (in gray), where the experiments of N fertilization of winter cereals were conducted. Monthly rainfall and temperatures (maximum, medium, and minimum), and soil organic matter distribution (Fontoura et al., 2015Fontoura SMV, Vieira RCB, Bayer C, Viero F, Anghinoni I, Moraes RP. Fertilidade do solo e seu manejo em sistema plantio direto no centro-sul do Paraná. Guarapuava: Fundação Agrária de Pesquisa Agropecuária; 2015.) are shown.

The climate in the region is humid subtropical (Cfb according to Köppen system), with an average annual rainfall of 1,900 mm well distributed throughout the year, with no dry season; rainfall is lowest in August, coinciding with the period of N fertilizer topdressing on winter cereals. Based on data from the weather stations of the FAPA, monthly rainfall ranges from 145 to 220 mm, except in August, with about 100 mm only. The average annual temperature is 16.8 °C and monthly averages range from 12.6 °C in July to 20.3 °C in January (Figure 1).

Experiments

The study was based on results of 72 experiments conducted from 2007 to 2012 by FAPA in areas cultivated under no-tillage for more than 20 years. In total, 52 experiments involved increasing rates of urea-N applied as topdressing to winter cereals cultivated in soybean-corn succession: 22 under wheat (Triticum aestivum L.) and 30 under barley (Hordeum vulgare L.) (Table 1). Another 20 experiments were conducted in 2008 and 2009, 10 with wheat and 10 with barley, in order to assess the N supply potential of the soils. The experiments were distributed in five sites (Guarapuava, Candói, Pinhão, Murakami, and Teixeira Soares) in the region managed by the Cooperativa Agrária Agroindustrial. The tables 2 and 3 show the chemical properties of the soils.

Table 1
Preceding crops, N rates, and cultivars used in the N fertilization experiments of wheat and barley conducted from 2007 to 2012 in the South-Central region of Paraná, Brazil
Table 2
Chemical properties of the soils where the nitrogen fertilization experiments with winter cereal crops were conducted in the South-Central region of Paraná
Table 3
Soil chemical properties in the South-Central region of Paraná where the experiments to determine the apparent N mineralization from soil organic matter were conducted

The experiments were arranged in a randomized block design with four replications. The applied N fertilizer consisted of common urea, applied as topdressing between the sprouting and elongation stages, generally corresponding to the stage of 4 to 6 leaves on the main stem (Haun, 1973Haun JR. Visual quantification of wheat development. Agron J. 1973;65:116-9. https://doi.org/10.2134/agronj1973.00021962006500010035x
https://doi.org/10.2134/agronj1973.00021...
).

The rates to obtain maximum economic efficiency (MEE) were calculated for those treatments where the response of crop yields to increasing N rates followed a polynomial behavior and were based on the average grain price from 2007 to 2012. The fertilizer : grain price ratio (price of kg of N per price of kg of grain) was 4.362 for wheat and 4.137 for barley [grain yield class I = grain yield × commercial classification (grain >2.5 mm)] (Brasil, 1996Brasil. Portaria no 691 de 22 de novembro de 1996. Brasília, DF: Ministério da Agricultura, Pecuária e Abastecimento; 1996 [acesso em 26 maio 2016]. Disponível em: http://www.agricultura.gov.br/legislacao/sislegis.
http://www.agricultura.gov.br/legislacao...
).

Grain yield expectation ranges and N rates to be applied

Expected yield ranges for wheat and barley were initially established from the overall grain yield for all experiments with increasing N rates. To the overall average, the standard deviation was added and subtracted, with appropriate rounding, adding two extreme values to the range. Thus, the expected yield ranges established for both cereals were <3.5, 3.5-4.5, 4.5-5.5, and >5.5 Mg ha-1.

The mean grain yields of wheat and barley, and the average N rate required to obtain yields within each expectancy range were estimated from the results of the 52 experiments involving application of variable N rates to winter cereals cultivated after soybean or corn. Polynomial equations fitted with average N rates (axis X) and the mean yields (axis Y) estimated for the different expected yield ranges were used to calculate the N rates required to obtain the mean yields for the 3.5-4.5 and 4.5-5.5 Mg ha-1 ranges, as well as those for the <3.5 and >5.5 Mg ha-1 ranges, leading to yields of 3.0 and 6.0 Mg ha-1, respectively.

Adjusting N rates for soils with different OM levels

The previously estimated N rates correspond to the N recommendations for winter cereals on soils with OM levels from 41 to 60 g dm-3, this range of OM was present in the soils of all 52 experiments (Table 2). These N rates, [N recommendation(OM range 41-60 g dm-3)] were adjusted for the rates to be applied to soils with OM levels <40 and >60 g dm-3, considering the difference in the amount of mineralized N (Δmineralized) compared to the soils with OM levels of 40 to 60 g dm-3, and also for the efficiency of urea-N applied in the fertilizer (Ef aN), using equations 1 and 2.

N recommendation O M r a n g e < 40 g d m - 3 = N rate O M r a n g e 40 - 60 g d m - 3 + N m i n e r a l i e d × 1 EfaN
N recommendation O M r a n g e > 60 g d m - 3 = N rate O M r a n g e 40 - 60 g d m - 3 - N m i n e r a l i e d × 1 EfaN

The difference in mineralized N (ΔNmineralized) between the soils with OM levels in the ranges <40 and >60 g dm-3, and those with levels in the range 41-60 g dm-3, was estimated from the apparent mineralization rate (AMR) of N in the soil according to Fontoura and Bayer (2009)Fontoura SMV, Bayer C. Adubação nitrogenada para alto rendimento de milho em plantio direto na região Centro-Sul do Paraná. Rev Bras Cienc Solo. 2009;33:1721-32. https://doi.org/10.1590/S0100-06832009000600021
https://doi.org/10.1590/S0100-0683200900...
. The AMR was based on the results of 20 experiments conducted in areas managed by the Cooperativa Agrária Agroindustrial in 2008 and 2009 (Table 3). The experiments involved cultivating wheat and barley in areas where all straw from the preceding crops had been removed from the soil surface. Under these conditions, it was assumed that all N absorbed by winter cereals was mineralized from soil OM and, thus, the apparent N mineralization rate can be calculated by equation 3 (Fontoura and Bayer, 2009)Fontoura SMV, Bayer C. Adubação nitrogenada para alto rendimento de milho em plantio direto na região Centro-Sul do Paraná. Rev Bras Cienc Solo. 2009;33:1721-32. https://doi.org/10.1590/S0100-06832009000600021
https://doi.org/10.1590/S0100-0683200900...
.

A p p a r e n t M i n e r a l i z a t i o n R a t e ( % ) = N a b s o r b e d S o i l N s t o c k × 100

where: N absorbed is the amount of N contained in dry matter (kg ha-1) of the aboveground plant biomass at the milky grain stage; and Soil N stock is that of N in the 0.00-0.20 m soil layer (kg ha-1), calculated from the soil N level and bulk density (results not shown). The term “apparent” applies to an indirect method used that may be influenced by possible losses of mineralized N not absorbed by the crop and was, therefore, not considered here. Also, this procedure takes only N contained in aboveground plant biomass into account, measured in 20 plants per plot, but not the N in root biomass.

The apparent N fertilizer efficiency for wheat and barley was estimated according to Mitchell and Tell (1977)Mitchell WH, Tell MR. Winter-annual cover crops for no-tillage corn production. Agron J. 1977;69:569-73. https://doi.org/10.2134/agronj1977.00021962006900040011x
https://doi.org/10.2134/agronj1977.00021...
(Equation 4):

E f a N = N A P f - N A P w f N a f × 100

where: Ef aN is the apparent efficiency of applied N (%); NAPf (kg ha-1) is the N amount absorbed by the plants supplied with N fertilizer; NAPwf (kg ha-1) is the N amount absorbed by the plants with no N fertilization; and Naf (kg ha-1) is the N rate applied via the fertilizer. The cumulative amount of N in aboveground biomass was determined by harvesting 20 plants per plot at the milky grain stage in both crops. The plants were dried and weighed to estimate dry matter yield and ground to determine the N concentration (Tedesco et al., 1995Tedesco MJ, Gianello C, Bissani CA, Bohnen H, Volkweiss SJ. Análises de solo, plantas e outros materiais. 2a ed rev ampl. Porto Alegre: Universidade Federal do Rio Grande do Sul; 1995. (Boletim Técnico, 5).). The term “apparent” efficiency here denotes that the efficiency was assessed by using an indirect method considering the amount of N in the aerial parts of the plant only.

Development and validation of N recommendation system for winter cereals

The previous evaluations and parameters were used to develop a system for calculating the amount of N fertilizer recommended to meet different yield expectations (<3.5, 3.5-4.5, 4.5-5.5, and >5.5 Mg ha-1) of wheat and barley (grain yield class I) grown on soils with different OM levels (<40, 41-60, and >60 g dm-3) under no-tillage after soybean or corn in the South-Central region of Paraná, Brazil.

The proposed system for winter cereals was validated by calculating the significance of the coefficients of the polynomial equations, relating the N rates determined in this work to those recommended by the Fertility Commission of Rio Grande do Sul and Santa Catarina (CQFS-RS/SC, 2016Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016.) for similar levels of soil OM, the preceding crop (pre-crop) and expected yield. Also, the suitability of the N rates recommended for the South-Central region of Paraná was assessed by the significance of the coefficients of the polynomial regression with the MEE rates calculated from the N fertilization response curves for wheat and barley.

RESULTS AND DISCUSSION

Expected grain yield ranges and N rates to be applied

The grain yields obtained testify to the high potential of soils in the South-Central region of Paraná for growing winter cereals; even without N fertilization, yields exceeded 4.0 Mg ha-1 and peaked at 6.0 Mg ha-1 (Figure 2). These results reflect advances in the management of these crops and the use of modern varieties with high potential yields (Barraclough et al., 2010Barraclough PB, Howarth JR, Jones J, Lopez-Bellido R, Parmar S, Shepherd CE, Hawkesford MJ. Nitrogen efficiency of wheat: genotypic and environmental variation and prospects for improvement. Eur J Agron. 2010;33:1-11. https://doi.org/10.1016/j.eja.2010.01.005
https://doi.org/10.1016/j.eja.2010.01.00...
; Beche et al., 2014Beche E, Benin G, Bornhofen E, Dalló SC, Sassi LHS, Oliveira R. Eficiência de uso de nitrogênio em cultivares de trigo pioneiras e modernas. Pesq Agropec Bras. 2014;49:948-57. https://doi.org/10.1590/S0100-204X2014001200005
https://doi.org/10.1590/S0100-204X201400...
).

Figure 2
The relationship between grain yield of wheat (a) and barley (b) grown after soybean or corn and supplied with increasing urea-N rates in the South-Central region of Paraná. This relationship was established based on average results from experiments conducted between 2007 and 2012 (22 with wheat and 30 with barley).

The amount of N applied increased linearly with increases in expected grain yield; in the OM range 41-60 g dm-3, applied N ranged from 30 to 143 kg ha-1 for wheat (Figure 3a) and 38 to 90 kg ha-1 for barley (Figure 3b). The pre-crop also influenced the N requirements of the winter cereals; thus, greater amounts of N were needed after corn than after soybean (Figures 2 and 3). The increased N rate required after corn was probably associated to N immobilization by soil microbiota during decomposition of corn residues, which has a high C/N ratio (Amado et al., 2002Amado TJC, Mielniczuk J, Aita C. Recomendação de adubação nitrogenada para o milho no RS e SC adaptada ao uso de culturas de cobertura do solo, sob sistema plantio direto. Rev Bras Cienc Solo. 2002;26:241-8. https://doi.org/10.1590/S0100-06832002000100025
https://doi.org/10.1590/S0100-0683200200...
; Braz et al., 2006Braz AJBP, Silveira PM, Kliemann HJ, Zimmermann FJP. Adubação nitrogenada em cobertura na cultura do trigo em sistema de plantio direto após diferentes culturas. Cienc Agrotec. 2006;30:193-8. https://doi.org/10.1590/S1413-70542006000200001
https://doi.org/10.1590/S1413-7054200600...
). Also, the amount of required N to reach the same grain yield range was higher in wheat than in barley, which may be a result from a higher crop capacity to remobilize absorbed N (Masclaux-Daubresse et al., 2010Masclaux-Daubresse C, Daniel-Vedele F, Dechorgnat J, Chardon F, Gaufichon L, Suzuki A. Nitrogen uptake, assimilation and remobilization in plants: challenges for sustainable and productive agriculture. Ann Bot-London. 2010;105:1141-57. https://doi.org/10.1093/aob/mcq028
https://doi.org/10.1093/aob/mcq028...
).

Figure 3
Expected grain yield of wheat (a) and barley (b) and urea-N rates required by the crops for a mean expected yield within the ranges 3.5-4.5 and 4.5-5.5 Mg ha-1 and yields of 3.0 and 6.0 Mg ha-1 within the expected yield ranges of <3.5 and >5.5 Mg ha-1, respectively, when cultivated after soybean and corn. Vertical bars indicate mean standard deviations.

Apparent mineralization rate of N from soil organic matter

The apparent mineralization rate (AMR) of soil N at the five studied sites ranged from 1.0 ± 0.17 to 1.5 ± 0.28 % (average 1.19 %) (Figure 4). Therefore, a 1.0 % value was assumed to be appropriate to estimate the differential supply of N (ΔNmineralized) (Equations 1 and 2) in soils with different OM ranges (<40 and >60 g dm-3) because it was the lowest value found over the two years at the five sites. The mineralization rate of N from soil OM depends on the soil type (Fontoura and Bayer, 2009)Fontoura SMV, Bayer C. Adubação nitrogenada para alto rendimento de milho em plantio direto na região Centro-Sul do Paraná. Rev Bras Cienc Solo. 2009;33:1721-32. https://doi.org/10.1590/S0100-06832009000600021
https://doi.org/10.1590/S0100-0683200900...
, climatic conditions (Liu et al., 2017)Liu Y, Wang C, He N, Wen X, Gao Y, Li S, Niu S, Butterbach-Bahl K, Luo Y, Yu G. A global synthesis of the rate and temperature sensitivity of soil nitrogen mineralization: latitudinal patterns and mechanisms. Glob Change Biol. 2017;23:455-64. https://doi.org/10.1111/gcb.13372
https://doi.org/10.1111/gcb.13372...
, and their seasonal changes. To estimate soil N supply for corn in the same region in the summer, Fontoura and Bayer (2009)Fontoura SMV, Bayer C. Adubação nitrogenada para alto rendimento de milho em plantio direto na região Centro-Sul do Paraná. Rev Bras Cienc Solo. 2009;33:1721-32. https://doi.org/10.1590/S0100-06832009000600021
https://doi.org/10.1590/S0100-0683200900...
used AMR = 3 %, resulting in a three times higher AMR than that estimated here for winter cereals, due to the effect of environmental conditions (temperature, mainly) on N mineralization in soil.

Figure 4
Apparent mineralization ratio of N from soil organic matter at five sites in the South-Central region of Paraná. Vertical bars indicate mean standard errors.

Based on AMR of 1 %, a soil N supply capacity of 35, 50, and 65 kg ha-1 was estimated for soils with OM ranges <40, 41-60, and >60 g dm-3, respectively. Thus, soils with OM contents in the ranges <40 and >60 g dm-3 delivered 15 kg N ha-1 less or more, respectively, compared to soils with OM ranges of 41-60 g dm-3. This difference in N (15 kg ha-1) is equivalent to the value of ΔNmineralized in equations 2 and 3.

Apparent efficiency of applied N

The apparent efficiency of N applied to wheat and barley cultivated after soybean or corn ranged from 42 to 56 % (Figure 5). The average apparent efficiency was 52 % and slightly higher for barley and after corn (Figure 5). However, using a single value for the efficiency of N fertilizer applied at the same time of year and under similar climatic conditions to wheat and barley led to an average efficiency of 50 %, which is consistent with reported values (Schirmann et al., 2013Schirmann J, Aita C, Giacomini SJ, Pujol SB, Giacomini DA, Gonzatto R, Olivo J. Inibidor de nitrificação e aplicação parcelada de dejetos de suínos nas culturas do milho e trigo. Rev Bras Cienc Solo. 2013;37:271-80. https://doi.org/10.1590/S0100-06832013000100028
https://doi.org/10.1590/S0100-0683201300...
; Espindula et al., 2014Espindula MC, Rocha VS, Souza MA, Campanharo M, Pimentel AJB. Urease inhibitor (NBPT) and efficiency of single or split application of urea in wheat crop. Ceres. 2014;61:273-9. https://doi.org/10.1590/S0034-737X2014000200016
https://doi.org/10.1590/S0034-737X201400...
).

Figure 5
Apparent efficiency of urea-N applied as topdressing to wheat and barley grown after soybean and corn in the South-Central region of Paraná. Vertical bars indicate mean standard errors.

The relatively low efficiency of applied N is a widely known fact, usually associated to heavy volatilization and leaching losses. In response, there have been some regional attempts to control N losses (mainly the volatilization of NH3) with specific management practices (irrigation, N incorporation) and urease inhibitors (Viero et al., 2014Viero F, Bayer C, Fontoura SMV, Moraes RP. Ammonia volatilization from nitrogen fertilizers in no-till wheat and maize in Southern Brazil. Rev Bras Cienc Solo. 2014;38:1515-25. https://doi.org/10.1590/S0100-06832014000500017
https://doi.org/10.1590/S0100-0683201400...
; Viero et al., 2015Viero F, Bayer C, Vieira RCB, Carniel E. Management of irrigation and nitrogen fertilizers to reduce ammonia volatilization. Rev Bras Cienc Solo. 2015;39:1737-43. https://doi.org/10.1590/01000683rbcs20150132
https://doi.org/10.1590/01000683rbcs2015...
; Corrêa et al., 2016Corrêa JC, Grohskopf MA, Nicoloso RS, Lourenço KS, Martini R. Organic, organomineral, and mineral fertilizers with urease and nitrification inhibitors for wheat and corn under no-tillage. Pesq Agropec Bras. 2016;51:916-24. https://doi.org/10.1590/S0100-204X2016000800003
https://doi.org/10.1590/S0100-204X201600...
; Silva et al., 2016Silva AGB, Sequeira CH, Sermarini RA, Otto R. Urease inhibitor NBPT on ammonia volatilization and crop productivity: a meta-analysis. Agron J. 2016;109:1-13. https://doi.org/10.2134/agronj2016.04.0200
https://doi.org/10.2134/agronj2016.04.02...
). Not only the ability to use applied N is important, but the efficiency in using applied N and converting it into grain yield also plays a central role. Some cultivars may have a low N absorption capacity but a high capacity to convert absorbed N into plant growth - and vice versa (Barraclough et al., 2010Barraclough PB, Howarth JR, Jones J, Lopez-Bellido R, Parmar S, Shepherd CE, Hawkesford MJ. Nitrogen efficiency of wheat: genotypic and environmental variation and prospects for improvement. Eur J Agron. 2010;33:1-11. https://doi.org/10.1016/j.eja.2010.01.005
https://doi.org/10.1016/j.eja.2010.01.00...
; Masclaux-Daubresse et al., 2010Masclaux-Daubresse C, Daniel-Vedele F, Dechorgnat J, Chardon F, Gaufichon L, Suzuki A. Nitrogen uptake, assimilation and remobilization in plants: challenges for sustainable and productive agriculture. Ann Bot-London. 2010;105:1141-57. https://doi.org/10.1093/aob/mcq028
https://doi.org/10.1093/aob/mcq028...
).

N rates recommended for wheat and barley

Nitrogen rates recommended for wheat and barley were established for three different soil OM ranges (<40, 41-60, and >60 g dm-3), four expected yield ranges (<3.5, 3.5-4.5, 4.5-5.5, and >5.5 Mg ha-1), and two pre-crops (soybean or corn) (Table 4).

Table 4
Indicated urea-N rates for crescent yield expectations of wheat and barley cultivated in soils with different soil organic matter contents and preceding summer crops (corn or soybean) in the South-Central region of Paraná

The N rates recommended for wheat grown after soybean and corn ranged from 30 to 150 kg ha-1 and 30 to 170 kg ha-1 respectively, the lowest rates corresponding to the soils with the highest OM levels (Table 4). In those cases, where SOM was high (>60 g dm-3) and expected grain yield low (<3.5 Mg ha-1), N application was indicated only at sowing (30 kg ha-1). On the other hand, the highest N rates were recommended for high expected grain yield (>5.5 Mg ha-1) and low OM soils. Raising wheat yields above 5.5 Mg ha-1 would not only require an adequate N supply, but also the absence of restrictive management and environmental factors limiting crop development (Amado et al., 2002Amado TJC, Mielniczuk J, Aita C. Recomendação de adubação nitrogenada para o milho no RS e SC adaptada ao uso de culturas de cobertura do solo, sob sistema plantio direto. Rev Bras Cienc Solo. 2002;26:241-8. https://doi.org/10.1590/S0100-06832002000100025
https://doi.org/10.1590/S0100-0683200200...
; Benin et al., 2012)Benin G, Bornhofen E, Beche E, Pagliosa ES, Silva CL, Pinnow C. Agronomic performance of wheat cultivars in response to nitrogen fertilization levels. Acta Sci Agron. 2012;34:275-83. https://doi.org/10.4025/actasciagron.v34i3.14468
https://doi.org/10.4025/actasciagron.v34...
such as plant diseases, weed infestation or water deficiency.

The N rates recommended for barley (Table 4) ranged from 30 to 130 kg ha-1 and were 10 kg ha-1 higher when the crop was grown after corn than after soybean. As an exception, the N rates with both pre-crops were equivalent when barley was cultivated on soils with high OM contents and low grain yield expectations. Increases in the expected grain yield (grain yield class 1) required more N fertilizer: 30 to 60 kg ha-1 for the highest expected grain yield (>5.5 Mg ha-1) compared to the <3.5 Mg ha-1 range. Whereas soils with low OM levels required greater amounts of applied N, those with high OM contents (>60 g dm-3) and a low expected grain yield (<3.5 Mg ha-1) only demanded N application at sowing (30 kg ha-1).

The N recommendation system for winter cereals in the South-Central region of Paraná (Table 4) followed the same principles underlying that for Rio Grande do Sul and Santa Catarina (CQFS-RS/SC, 2016Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016.) and Paraguay (Wendling et al., 2007Wendling A, Eltz FLF, Cubilla MM, Amado TJC, Mielniczuk J, Lovato T. Recomendação de adubação nitrogenada para trigo em sucessão ao milho e soja sob sistema plantio direto no Paraguai. Rev Bras Cienc Solo. 2007;31:985-94. https://doi.org/10.1590/S0100-06832007000500015
https://doi.org/10.1590/S0100-0683200700...
), and also that for corn in Rio Grande do Sul and Santa Catarina (Amado et al., 2002Amado TJC, Mielniczuk J, Aita C. Recomendação de adubação nitrogenada para o milho no RS e SC adaptada ao uso de culturas de cobertura do solo, sob sistema plantio direto. Rev Bras Cienc Solo. 2002;26:241-8. https://doi.org/10.1590/S0100-06832002000100025
https://doi.org/10.1590/S0100-0683200200...
), and Paraná (Fontoura and Bayer, 2009Fontoura SMV, Bayer C. Adubação nitrogenada para alto rendimento de milho em plantio direto na região Centro-Sul do Paraná. Rev Bras Cienc Solo. 2009;33:1721-32. https://doi.org/10.1590/S0100-06832009000600021
https://doi.org/10.1590/S0100-0683200900...
). In the previous systems, the recommended N rates were higher when the winter cereals were preceded by a grass species - as were our recommendations of N rates after corn. This result may have been a consequence of N immobilization during decomposition of residues with a high C/N ratio or of the increased amounts of N supplied from biomass mineralization of the legume pre-crop (Amado et al., 2002Amado TJC, Mielniczuk J, Aita C. Recomendação de adubação nitrogenada para o milho no RS e SC adaptada ao uso de culturas de cobertura do solo, sob sistema plantio direto. Rev Bras Cienc Solo. 2002;26:241-8. https://doi.org/10.1590/S0100-06832002000100025
https://doi.org/10.1590/S0100-0683200200...
; Braz et al., 2006Braz AJBP, Silveira PM, Kliemann HJ, Zimmermann FJP. Adubação nitrogenada em cobertura na cultura do trigo em sistema de plantio direto após diferentes culturas. Cienc Agrotec. 2006;30:193-8. https://doi.org/10.1590/S1413-70542006000200001
https://doi.org/10.1590/S1413-7054200600...
). Likewise, the amount of N to be applied to soils with a high OM content was small compared to those containing little OM as a result of the high N supply from organic N mineralization in the soil (Liu et al., 2017Liu Y, Wang C, He N, Wen X, Gao Y, Li S, Niu S, Butterbach-Bahl K, Luo Y, Yu G. A global synthesis of the rate and temperature sensitivity of soil nitrogen mineralization: latitudinal patterns and mechanisms. Glob Change Biol. 2017;23:455-64. https://doi.org/10.1111/gcb.13372
https://doi.org/10.1111/gcb.13372...
).

The recommended N rate for both wheat and barley includes the suggestion of an application of 30 kg ha-1 at sowing; the remainder should be applied as topdressing between sprouting and elongation (usually with 4-6 leaves on the main stem) (Haun, 1973Haun JR. Visual quantification of wheat development. Agron J. 1973;65:116-9. https://doi.org/10.2134/agronj1973.00021962006500010035x
https://doi.org/10.2134/agronj1973.00021...
). Therefore, 30 kg ha-1 is the lowest indicated N rate because it can be applied to both cereals. Some cultivar-specific factors of the cereals, such as susceptibility to wind damage and disease, should be considered at the time of N application (Minella, 2015Minella E. Indicações técnicas para a produção de cevada cervejeira nas safras 2015 e 2016. In: XXX Reunião Nacional de Pesquisa de Cevada; 2015; Passo Fundo. Passo Fundo: Embrapa Trigo; 2015. (Sistemas de Produção 8).; Cunha et al., 2016Cunha GR, Caierão E, Rosa AC. Informações técnicas para trigo e triticale - safra 2016. In: 9a Reunião da Comissão Brasileira de Pesquisa de Trigo e Triticale; 2015; Passo Fundo. Passo Fundo: Biotrigo Genética; 2016.). Splitting the N fertilizer rate or using a growth inhibitor can be effective to reduce these risks (Espindula et al., 2010Espindula MC, Rocha VS, Souza MA, Grossi JAS, Souza LT. Doses e formas de aplicação de nitrogênio no desenvolvimento e produção da cultura do trigo. Cienc Agrotec. 2010;34:1404-11. https://doi.org/10.1590/S1413-70542010000600007
https://doi.org/10.1590/S1413-7054201000...
; Teixeira Filho et al., 2010Teixeira Filho MCM, Buzetti S, Andreotti M, Arf O, Benett CGS. Doses, fontes e épocas de aplicação de nitrogênio em trigo irrigado em plantio direto. Pesq Agropec Bras. 2010;45:797-804. https://doi.org/10.1590/S0100-204X2010000800004
https://doi.org/10.1590/S0100-204X201000...
).

Validation of N recommendations for wheat and barley

The N rates recommended for wheat and barley in the South-Central region of Paraná (Table 4) had a significant linear relationship (R2 = 0.66, p<0.02) with the N rates indicated by the Fertility Commission of Rio Grande do Sul and Santa Catarina (CQFS-RS/SC, 2016Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016.) (Figure 6). Overall, considering similar SOM levels and yield expectations, the N rates recommended for wheat after soybean in the South-Central region of Paraná were 10-20 kg ha-1 higher than those recommended by CQFS-RS/SC (2016)Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016.. On the other hand, those for wheat after corn were virtually identical.

Figure 6
Relationship of indicated urea-N rates for wheat after soybean (a) and after corn (b) and barley after soybean (c) and after corn (d) in Rio Grande do Sul and Santa Catarina (CQFS-RS/SC, 2016Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016.), to the proposed N rates for the South-Central region Paraná. Dotted lines represent linear regression curves and solid lines 95 % of the confidence interval.

The N rates recommended for barley sown after soybean on soils with a low OM content and low expected yield in the South-Central region of Paraná are similar to those for the states of Rio Grande do Sul and Santa Catarina (CQFS-RS/SC, 2016Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016.). For barley after corn, however, the rates recommended by CQFS-RS/SC (2016)Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016. were higher whichever the expected yield, but especially (up to 35 kg ha-1) for higher expectations. It should be noted that the N recommendations for barley in the South-Central region of Paraná were based on grain yield class I, whereas those for Rio Grande do Sul and Santa Catarina are based on the total yield of barley grain, which tends to widen the differences.

The increased N rates recommended for barley grown after corn in Rio Grande do Sul and Santa Catarina may have arisen at least partly from the determination procedure, which considers immobilization of N from corn residues twice. In fact, CQFS-RS/SC (2016)Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016. considered N immobilization once when indicating an N rate 20 kg ha-1 higher after corn than after soybean for a grain yield of 3.0 Mg ha-1, and a second time when indicating a further 10 kg N ha-1 after corn than after soybean for each 1.0 Mg ha-1 above a yield of 3.0 Mg ha-1. Since this procedure distinguishes the N rate for the baseline yield and that for each 1.0 Mg ha-1 additional yield, the effect of N immobilization on N rates is duplicated. This may partly account for the higher rates for the higher yield expectations in Rio Grande do Sul and Santa Catarina compared to our rates for the South-Central region of Paraná. Even though our N rates for wheat are similar to the recommendations of CQFS-RS/SC (2016)Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016., considering immobilization twice in the recommendations for Rio Grande do Sul and Santa Catarina is unsustainable because N immobilization is not related to the expected crop yield. Therefore, the recommendations for these two states should be revised to determine a single differential N rate for the baseline yield of barley or wheat after soybean or corn, and further amounts of N for each 1 Mg ha-1 additional yield, irrespective of the pre-crop.

The recommended N rates were validated by correlation with the estimated MEE rates for wheat and barley (Figure 7). The N rates recommended and MME rates were related with acceptable significance (p<0.0971 for wheat and p<0.0001 for barley), irrespective of soil OM content and expected yield.

Figure 7
Relationship of maximum economic efficiency rates and urea-N rates indicated for wheat (a) and barley (b) in the South-Central region of Paraná. Dotted lines represent linear regression curves and solid lines 95 % of the confidence interval.

The average MEE rate for wheat cultivated after soybean and corn was 91 and 105 kg ha-1, respectively (Table 5), corresponding to grain yield expectations in the range from 4.5 to 5.5 Mg ha-1. These MEE rates differ by less than 12 % from the N rates recommended (Table 4) for the same expected yield range and soil OM content (41-60 g dm-3). The MEE rate for barley grown after soybean and corn was 55 and 76 kg ha-1, respectively (Table 6). These rates are 21 and 24 % lower than the N rates recommended for barley grown on soil with soil OM content in the same range (41-60 g dm-3) and grain yields in the ranges 4.5-5.5 and >5.5 Mg ha-1, respectively.

Table 5
Fitted equation of grain yield for wheat grown after soybean and corn according to the applied urea-N rate (kg ha-1), maximum economic efficiency (MEE) rate, and respectively yields
Table 6
Fitted equation of grain yield for barley grown after soybean and corn according to the applied urea-N rate (kg ha-1), maximum economic efficiency (MEE) rate, and respective yields

In view of the complexity of the factors (e.g., soil OM content and fertility, crop variety and management, and climatic conditions) potentially affecting the N response or demand, the N rates recommended for the South-Central region of Paraná (Table 4) are quite similar to those recommended by CQFS-RS/SC (2016)Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016. and the MME N rates similar to those indicated for the studied region, and can therefore be used as reference in the management of N fertilization of winter cereals by regional producers and agricultural technicians.

CONCLUSIONS

We established the N fertilizer rates for wheat and barley in the South-Central region of Paraná, Southern Brazil. The indicated N rates (30-170 kg ha-1 for wheat and 10-130 kg ha-1 for barley) are generally consistent with those for Rio Grande do Sul and Santa Catarina, and also with the estimated N rates needed to obtain the maximum economic efficiency. The N rates increased for crescent grain yields expectation, low soil organic matter levels, and when the preceding summer crop was corn. The proposed recommendation can be used as N fertilization references for winter wheat and barley by regional producers and agricultural technicians.

ACKNOWLEDEGMENTS

The authors are grateful to the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) of Brazil and the Fundação Agrária de Pesquisa Agropecuária (FAPA)for funding this research; to the FAPA staff for performing the experiments; and to the agronomists of the Cooperativa Agrária Agroindustrial for the exchange of information and support in the development of the proposed N rate recommendation system.

REFERENCES

  • Agrária. Annual Report [internet]. Guarapuava: Agrária; 2016 [acesso em 17 de novembro 2016]. Disponível em: http://www.agraria.com.br/en/relatorio_anual.php
    » http://www.agraria.com.br/en/relatorio_anual.php
  • Amado TJC, Mielniczuk J, Aita C. Recomendação de adubação nitrogenada para o milho no RS e SC adaptada ao uso de culturas de cobertura do solo, sob sistema plantio direto. Rev Bras Cienc Solo. 2002;26:241-8. https://doi.org/10.1590/S0100-06832002000100025
    » https://doi.org/10.1590/S0100-06832002000100025
  • Barraclough PB, Howarth JR, Jones J, Lopez-Bellido R, Parmar S, Shepherd CE, Hawkesford MJ. Nitrogen efficiency of wheat: genotypic and environmental variation and prospects for improvement. Eur J Agron. 2010;33:1-11. https://doi.org/10.1016/j.eja.2010.01.005
    » https://doi.org/10.1016/j.eja.2010.01.005
  • Beche E, Benin G, Bornhofen E, Dalló SC, Sassi LHS, Oliveira R. Eficiência de uso de nitrogênio em cultivares de trigo pioneiras e modernas. Pesq Agropec Bras. 2014;49:948-57. https://doi.org/10.1590/S0100-204X2014001200005
    » https://doi.org/10.1590/S0100-204X2014001200005
  • Benin G, Bornhofen E, Beche E, Pagliosa ES, Silva CL, Pinnow C. Agronomic performance of wheat cultivars in response to nitrogen fertilization levels. Acta Sci Agron. 2012;34:275-83. https://doi.org/10.4025/actasciagron.v34i3.14468
    » https://doi.org/10.4025/actasciagron.v34i3.14468
  • Brasil. Portaria no 691 de 22 de novembro de 1996. Brasília, DF: Ministério da Agricultura, Pecuária e Abastecimento; 1996 [acesso em 26 maio 2016]. Disponível em: http://www.agricultura.gov.br/legislacao/sislegis
    » http://www.agricultura.gov.br/legislacao/sislegis
  • Braz AJBP, Silveira PM, Kliemann HJ, Zimmermann FJP. Adubação nitrogenada em cobertura na cultura do trigo em sistema de plantio direto após diferentes culturas. Cienc Agrotec. 2006;30:193-8. https://doi.org/10.1590/S1413-70542006000200001
    » https://doi.org/10.1590/S1413-70542006000200001
  • Comissão de Química e Fertilidade do Solo - CQFS-RS/SC. Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina. 11a ed. Porto Alegre: Sociedade Brasileira de Ciência do Solo - Núcleo Regional Sul; 2016.
  • Corrêa JC, Grohskopf MA, Nicoloso RS, Lourenço KS, Martini R. Organic, organomineral, and mineral fertilizers with urease and nitrification inhibitors for wheat and corn under no-tillage. Pesq Agropec Bras. 2016;51:916-24. https://doi.org/10.1590/S0100-204X2016000800003
    » https://doi.org/10.1590/S0100-204X2016000800003
  • Cunha GR, Caierão E, Rosa AC. Informações técnicas para trigo e triticale - safra 2016. In: 9a Reunião da Comissão Brasileira de Pesquisa de Trigo e Triticale; 2015; Passo Fundo. Passo Fundo: Biotrigo Genética; 2016.
  • De Bona FD, De Mori C, Wietholter S. Manejo nutricional da cultura do trigo. Piracicaba: IPNI; 2016. (Informações Agronômicas, 154).
  • Espindula MC, Rocha VS, Souza MA, Campanharo M, Pimentel AJB. Urease inhibitor (NBPT) and efficiency of single or split application of urea in wheat crop. Ceres. 2014;61:273-9. https://doi.org/10.1590/S0034-737X2014000200016
    » https://doi.org/10.1590/S0034-737X2014000200016
  • Espindula MC, Rocha VS, Souza MA, Grossi JAS, Souza LT. Doses e formas de aplicação de nitrogênio no desenvolvimento e produção da cultura do trigo. Cienc Agrotec. 2010;34:1404-11. https://doi.org/10.1590/S1413-70542010000600007
    » https://doi.org/10.1590/S1413-70542010000600007
  • Fontoura SMV, Bayer C. Adubação nitrogenada para alto rendimento de milho em plantio direto na região Centro-Sul do Paraná. Rev Bras Cienc Solo. 2009;33:1721-32. https://doi.org/10.1590/S0100-06832009000600021
    » https://doi.org/10.1590/S0100-06832009000600021
  • Fontoura SMV, Vieira RCB, Bayer C, Viero F, Anghinoni I, Moraes RP. Fertilidade do solo e seu manejo em sistema plantio direto no centro-sul do Paraná. Guarapuava: Fundação Agrária de Pesquisa Agropecuária; 2015.
  • Haun JR. Visual quantification of wheat development. Agron J. 1973;65:116-9. https://doi.org/10.2134/agronj1973.00021962006500010035x
    » https://doi.org/10.2134/agronj1973.00021962006500010035x
  • Liu Y, Wang C, He N, Wen X, Gao Y, Li S, Niu S, Butterbach-Bahl K, Luo Y, Yu G. A global synthesis of the rate and temperature sensitivity of soil nitrogen mineralization: latitudinal patterns and mechanisms. Glob Change Biol. 2017;23:455-64. https://doi.org/10.1111/gcb.13372
    » https://doi.org/10.1111/gcb.13372
  • Masclaux-Daubresse C, Daniel-Vedele F, Dechorgnat J, Chardon F, Gaufichon L, Suzuki A. Nitrogen uptake, assimilation and remobilization in plants: challenges for sustainable and productive agriculture. Ann Bot-London. 2010;105:1141-57. https://doi.org/10.1093/aob/mcq028
    » https://doi.org/10.1093/aob/mcq028
  • Minella E. Indicações técnicas para a produção de cevada cervejeira nas safras 2015 e 2016. In: XXX Reunião Nacional de Pesquisa de Cevada; 2015; Passo Fundo. Passo Fundo: Embrapa Trigo; 2015. (Sistemas de Produção 8).
  • Mitchell WH, Tell MR. Winter-annual cover crops for no-tillage corn production. Agron J. 1977;69:569-73. https://doi.org/10.2134/agronj1977.00021962006900040011x
    » https://doi.org/10.2134/agronj1977.00021962006900040011x
  • Schirmann J, Aita C, Giacomini SJ, Pujol SB, Giacomini DA, Gonzatto R, Olivo J. Inibidor de nitrificação e aplicação parcelada de dejetos de suínos nas culturas do milho e trigo. Rev Bras Cienc Solo. 2013;37:271-80. https://doi.org/10.1590/S0100-06832013000100028
    » https://doi.org/10.1590/S0100-06832013000100028
  • Silva AGB, Sequeira CH, Sermarini RA, Otto R. Urease inhibitor NBPT on ammonia volatilization and crop productivity: a meta-analysis. Agron J. 2016;109:1-13. https://doi.org/10.2134/agronj2016.04.0200
    » https://doi.org/10.2134/agronj2016.04.0200
  • Soil Survey Staff. Keys to soil taxonomy. 12th ed. Washington, DC: United States Department of Agriculture, Natural Resources Conservation Service; 2014.
  • Tedesco MJ, Gianello C, Bissani CA, Bohnen H, Volkweiss SJ. Análises de solo, plantas e outros materiais. 2a ed rev ampl. Porto Alegre: Universidade Federal do Rio Grande do Sul; 1995. (Boletim Técnico, 5).
  • Teixeira Filho MCM, Buzetti S, Andreotti M, Arf O, Benett CGS. Doses, fontes e épocas de aplicação de nitrogênio em trigo irrigado em plantio direto. Pesq Agropec Bras. 2010;45:797-804. https://doi.org/10.1590/S0100-204X2010000800004
    » https://doi.org/10.1590/S0100-204X2010000800004
  • Viero F, Bayer C, Fontoura SMV, Moraes RP. Ammonia volatilization from nitrogen fertilizers in no-till wheat and maize in Southern Brazil. Rev Bras Cienc Solo. 2014;38:1515-25. https://doi.org/10.1590/S0100-06832014000500017
    » https://doi.org/10.1590/S0100-06832014000500017
  • Viero F, Bayer C, Vieira RCB, Carniel E. Management of irrigation and nitrogen fertilizers to reduce ammonia volatilization. Rev Bras Cienc Solo. 2015;39:1737-43. https://doi.org/10.1590/01000683rbcs20150132
    » https://doi.org/10.1590/01000683rbcs20150132
  • Wendling A, Eltz FLF, Cubilla MM, Amado TJC, Mielniczuk J, Lovato T. Recomendação de adubação nitrogenada para trigo em sucessão ao milho e soja sob sistema plantio direto no Paraguai. Rev Bras Cienc Solo. 2007;31:985-94. https://doi.org/10.1590/S0100-06832007000500015
    » https://doi.org/10.1590/S0100-06832007000500015

Publication Dates

  • Publication in this collection
    2017

History

  • Received
    11 Jan 2017
  • Accepted
    16 May 2017
Sociedade Brasileira de Ciência do Solo Secretaria Executiva , Caixa Postal 231, 36570-000 Viçosa MG Brasil, Tel.: (55 31) 3899 2471 - Viçosa - MG - Brazil
E-mail: sbcs@ufv.br