Corn agronomic traits and recovery of nitrogen from fertilizer during crop season and off-season

Abstract: The objective of this work was to evaluate corn agronomic traits in a cultivation subjected to different N rates, during the fall-winter (off-season) and spring-summer crop seasons, and N recovery from fertilizer. The experiment was set up in a randomized complete block design with four replicates, in a 5x2 factorial arrangement, with the following treatments: five N topdressing rates - 0, 30, 60, 90, and 120 kg ha-1 -, using urea as source; and two crop seasons, fall-winter and spring-summer. The following variables were determined: plant height, height of the first ear insertion, number of grains per ear, diameter and length of ear, 1,000-grain weight, N concentration in the leaves and grains, grain-protein concentration, grain yield, N recovery from fertilizer, and soil-N supply. Nitrogen rates in the fertilizer in the fall-winter season had no effect on grain yield, although corn agronomic traits showed a greater reliance on fertilizer-N rates in that season than in the spring-summer, which is a season associated to a greater capacity of soil-N supply to plants. The quantification of soil-N supply enabled knowing the nutrient dynamics during the fall-winter and the spring-summer seasons, which may be useful to guide N fertilization of corn.摘要：本研究旨在评估秋冬（茬口淡季）与春夏两季种植季下，施加不同氮肥施用量的玉米农艺性状，以及肥料氮素回收率。本试验采用随机完全区组设计（randomized complete block design），设置4次重复，采用5×2因子排列方案，处理设置如下：5种氮肥追施用量——0、30、60、90和120 kg·ha⁻¹，氮肥源为尿素；以及2个种植季，即秋冬季与春夏季。本研究测定的指标包括：株高、第一果穗着生高度、每穗粒数、果穗直径与长度、千粒重、叶片与籽粒中的氮浓度、籽粒蛋白质浓度、籽粒产量、肥料氮素回收率以及土壤供氮量。研究结果显示，秋冬季施加的氮肥施用量对籽粒产量无显著影响，尽管该季玉米农艺性状对氮肥施用量的依赖程度高于春夏季，而春夏季土壤向植株供氮的能力更强。对土壤供氮量的量化，有助于明确秋冬季与春夏季的养分动态，可用于指导玉米氮肥施用。