This study aimed to evaluate whether soybean benefits from N fertilizer rates applied to previous corn in a corn-soybean succession in Brazil´s Midwest region.Editors: Andreas Carstensen, Kristian Holst Laursen, Jan Kofod Schjorring

CARVALHO, M. da C. S.

HOROWITZ, N.

NASCENTE, A. S.

TEIXEIRA, P. C.

English

Repository Open Access to Scientific Information from Embrapa

Does nitrogen fertilizer application rate to corn affect yield of subsequent soybean?  Maria da Conceição Santana Carvalho1, Nelson Horowitz2, Adriano Stephan Nascente1, Paulo César Teixeira3  1Embrapa Arroz e Feijão, Rodovia GO-462, Km 12, Caixa Postal 179 CEP: 75375-000 - Santo Antônio de Goiás, BRAZIL (maria.carvalho@embrapa.br; adriano.nascente@embrapa.br).  2Yara Brasil Fertilizantes SA, Av. Carlos Gomes 1672, Porto Alegre, RS, BRAZIL, CEP: 90480-002 (nelson.horowitz@yara.com). 3Embrapa Solos, Rua Jardim Botânico, nº 1024, Bairro Jardim Botânico, CEP: 22460-000, RJ, BRAZIL (paulo.c.teixeira@embrapa.br).   INTRODUCTION Soybean (Glycine max [L.] Merr) and corn (Zea mays L.) succession is the main cropping system used in Brazil. Soybean is the main crop with production in 2015/16 growing season of 95.4 million tons from a harvested area of 33.2 million hectares (CONAB, 2017). Brazil´s soybean average yield ranged from 2,629 to 3,115 kg ha−1 in the last ten growing seasons, although some farmers reached about 4,200 kg ha−1. Soybean yield potential has been estimated to be in the range of 4,200-5,600 kg ha-1, depending on the region (Sentelhas et. al., 2015). Corn is also a major crop in Brazil with production in 2015/16 growing season estimated of 81.5 million tons from a harvested area of 15.9 million hectares (CONAB, 2017). Soybean has high nitrogen (N) requirement of about 80 kg of N to produce 1,000 kg of grains. Biological N2 fixation (BNF) by means of inoculation with Bradyrhizobium spp. inoculant is the recommended source for meeting the N requirement of soybean in Brazil. Recently consultants and farmers have controversial opinions on whether BNF could provide full N requirement of soybean to achieve yields levels above 3,600 kg ha-1. Results from field trials performed in three ecoregions of Brazil demonstrated that basal and topdressing N (separately or combined) had strong negative effects on nodulation and may have negative impact on crop yields (Kaschuk et al., 2016). However, there is lack of information regarding the effect of increasing N fertilizer rates in this cropping system, instead of N application directly to soybean. This study aimed to evaluate whether soybean benefits from N fertilizer rates applied to previous corn in a corn-soybean succession in Brazil´s Midwest region.  METHODS A field trial was performed at Embrapa´s Experimental Station located in the city of Santo Antônio de Goiás, Goiás, Brazil. We used a randomized complete blocks design arranged in a 3x2+1 factorial scheme with five replications. N fertilizer was applied only to corn, at three N rates (75, 150 and 225 kg ha-1) combined with two N sources (urea and calcium ammonium nitrate - CAN), and a control (without N application). The plots in the corn-soybean succession consisted of 8 ten-meter-long rows of corn spaced 0.90 m apart in 2013/14 growing season and 16 ten-meter-long rows of soybean spaced 0.45 m apart in 2014/15 growing season. We evaluated in both crops: grain yield, N leaf content, and N uptake in above ground biomass.  The analysis of variance (F test) was performed for all variables by using SAS statistical software (SAS Institute 1999).  RESULTS AND DISCUSSION Considering that the experimental area was in fallow and covered with Brachiaria ruziziensis during the last three years before starting the experiment, the soil disturbance caused by the XVIII INTERNATIONAL PLANT NUTRITION COLLOQUIUM 19-24 AUGUST 2017 • COPENHAGEN | DENMARK www.ipnc2017.org451incorporation of limestone, associated with high level of soil organic matter (3.4 g kg-1) and good weather conditions during the corn cycle, enabled to reach high corn yield, even without the application of nitrogen fertilizer (Table 1). The N rates had no effect on corn grain yield, but increased N content in leaves and N accumulation in straw and grains, regardless of the N source.  About 1.0 kg of N per each 60-kg bag of corn grains were exported with the harvest. Thus, considering that the average grain yield ranged from 189 to 205 bags per hectare, the application of N rates lower than these values resulted in negative nitrogen balance (Table 1). In short-term, soybean did not benefit from the application of higher rates of nitrogen to corn in the previous growing season, considering that both soybean yield and N uptake in aboveground biomass were not positively affected by the N fertilization of corn (Table 1).  Note that soybean yield in the treatment without N fertilization tended to be higher than that ones with N fertilization (Pr=0.10).  Table 1. Corn and soybean grain yield, nitrogen content in leaves and nitrogen accumulation in aboveground biomass in response to the application of nitrogen rates and sources to corn in the corn-soybean rotation. Santo Antonio de Goiás, GO, Brazil.   CONCLUSION  In short-term, both soybean yield and N uptake by soybean plants were not positively affected by the application of higher N rates to previous corn in the corn-soybean crop sequence.  REFERENCES CONAB – Companhia Nacional de Abastecimento. (2017) Safras: séries históricas. Accessed on January 30, 2017 at  http://www.conab.gov.br. Sentelhas, P.C., Battisti, R., Câmara, G.M.S., Farias, J.R.B., Hampf, A.C. and Nendel, C. (2015) The soybean yield gap in Brazil – magnitude, causes and possible solutions for sustainable production. J. Agr. Sci., 153(8):1394-1411. Kaschuka, G., Nogueira, M.A., Luca, M.J., Hungria, M. (2016) Response of determinate and indeterminate soybean cultivars to basal and topdressing N fertilization compared to sole inoculation with Bradyrhizobium. Field Crops Research, 195(15):21-27.  SAS Institute Inc. (1999). SAS/GRAPH Software: version 9.2, Cary, NC: SAS Institute Inc. N rateGrain yieldN leaf contentN remained in the strawN accumulated in grainsN  balance/1Grain yieldN leaf contentN uptake in abovegroundg kg-1 kg ha-1 g kg-1 kg ha-1CAN/2 75 11629 35.8 230 186 -111 4389 45.8 309CAN 150 12307 36.1 234 205 -55 4169 45.6 292CAN 225 11987 38.1 275 203 22 4506 43.9 292Urea 75 11782 36.2 236 189 -114 4293 43.3 302Urea 150 12070 36.3 232 200 -50 4046 43.0 278Urea 225 11471 40.0 256 194 31 4328 44.5 299Control 0 11344 32.9 173 175 -175 4639 44.2 294Average 11798 36.5 234 193 -65 4339 44.3 295C. V. (%) 6.3 7.3 17.7 5.6  - 9.6 4.8 13.2DFN sources (S) 1 0.47 0.39 0.85 0.44  - 0.39 0.06 0.75N rates (R) 2 0.28 <0.01 <0.01 <0.01  - 0.25 0.92 0.49S x R 2 0.61 0.74 0.89 0.53  - 0.97 0.18 0.81(S x R) x Control 1 0.16 <0.01 <0.01 <0.01  - 0.10 0.88 0.93/1 N balance = Input as fertilizer - exported in grains; DF = degree of freedom.   C.V. = coeficient of variation/2 CAN = calcium ammonium nitrateN source2014/2015 - SoybeanANOVA - Probability of F test (Pr>F)2013/2014 growing season - Corn -------------------- kg ha-1 -------------------- ------- kg ha-1 --------XVIII INTERNATIONAL PLANT NUTRITION COLLOQUIUM 19-24 AUGUST 2017 • COPENHAGEN | DENMARK www.ipnc2017.org452

Does nitrogen fertilizer application rate to corn affect yield of subsequent soybean?

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Does nitrogen fertilizer application rate to corn affect yield of subsequent soybean?

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