Increased grain yield can be obtained via an interaction between plants and growth-promoting microorganisms. The Bradyrhizobium spp. are capable of fixing atmospheric nitrogen in soybeans [ Glycine max (L.) Merril], and Azospirillum spp. induce the synthesis of phytohormones. The aim of this study was to evaluate inoculation with Bradyrhizobium and co-inoculation with Bradyrhizobium + Azospirillum brasilense in soybeans in combination with the application a topdressing of 0, 75 or 150 kg of N ha -1 of urea during the reproductive stage. Three soybean cultivars (BMX Ativa, TEC 6029 and BMX Pot?ancia), were tested in field experiments in Santa Maria, RS, Brazil, during two agricultural years (2013/2014 and 2014/2015) and two sowing times. Morphological, nodulation and yield components were evaluated. Co-inoculation increased the grain yield by 240 kg ha -1 compared with conventional inoculation. When co-inoculated, cultivars BMX Ativa, TEC 6029 and BMX Pot?ancia showed increased grain yields of 6, 4 and 12%, respectively. The application of 150 kg ha -1 of N as a topdressing increased the grain yield by 300 kg ha -1 in the co-inoculated cultivars TEC 6029 and BMX Pot?ancia, but without a financial return. When inoculated only with Bradyrhizobium , the cultivars did not respond positively to the application of urea.
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机译：通过植物与促进生长的微生物之间的相互作用，可以提高谷物的产量。缓生根瘤菌能够固定大豆中的大气氮[Glycine max（L.）Merril]和Azospirillum spp。诱导植物激素的合成。这项研究的目的是评估在大豆育苗期接种大豆根瘤菌和与大豆根瘤菌+巴西螺旋藻共接种，并配合施用追肥量为0、75或150 kg N ha -1的尿素。在两个农业年度（2013/2014年和2014/2015年）和两个播种期，在巴西圣塔玛丽亚的三个田间试验中测试了三个大豆品种（BMX Ativa，TEC 6029和BMX Pot？ancia）。评价形态，结瘤和产量成分。与常规接种相比，共接种可将谷物产量提高240 kg ha -1。当共同接种时，BMX Ativa，TEC 6029和BMX Potanancia品种的谷物单产分别提高了6％，4％和12％。在共同接种的品种TEC 6029和BMX Potanancia中，施用150 kg ha -1的氮作为追肥，可使谷物产量增加300 kg ha -1，但没有经济回报。仅接种根瘤菌时，品种对尿素的施用没有积极反应。
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