Timing and growing conditions of nitrogen topdressing influence the grain yield and protein content of four wheat cultivars

ABSTRACT The application of an adequate rate and splitting of nitrogen is essential for wheat grain yield and protein content. The aim of this work was to adjust nitrogen management approaches regarding agronomic performance and protein content of wheat cultivars in various environments. Field experiments were conducted under no-tillage system on soybean mulch during the 2011 and 2012 growing seasons in Londrina and Pato Branco regions. The experimental design was a randomized block in split plot with four replicates. Four wheat cultivars (IPR Catuara TM, BRS Gaivota, Quartzo, CD 120) were tested with six nitrogen (N) management forms. Were evaluated: number of ears per unit area (NEA); plant height (PH); thousand-kernel weight (TKW); test weight (TW); grain yield (GY); and protein content (PC). The combined ANOVA (p ? 0.01) and Tukey’s test (p ? 0.01) were used. The interaction between cultivars and environments influence all yield components, GY and PC. The interaction management forms of N and environments affected the TKW, NEA, GY and PC. The results showed that in low-rainfall environments, nitrogen topdressing could be suppressed with no negative effects on GY or PC. Under ideal weather conditions, the GY of wheat cultivars was enhanced on application of 60 kg.ha–1 N of urea at the beginning of tillering as well 20 kg.ha–1 of N at booting. Matching the appropriate cultivars to the ideal growth environment is essential for achieving high GY values. The nitrogen forms on the topdressing do not influence the PC of cultivars in Pato Branco.摘要 合理的施氮总量与施氮分期配置对小麦籽粒产量及蛋白质含量至关重要。本研究旨在针对不同环境下小麦品种的农艺性状表现与蛋白质含量，优化氮肥管理方案。试验于2011和2012年生长季，在隆德里纳（Londrina）与帕托布兰科（Pato Branco）地区的大豆秸秆覆盖免耕系统下开展。试验采用裂区随机区组设计，设置4次重复。供试小麦品种共4个（IPR Catuara TM、BRS Gaivota、Quartzo、CD 120），搭配6种氮肥管理模式。供试测定指标包括：单位面积穗数（number of ears per unit area, NEA）、株高（plant height, PH）、千粒重（thousand-kernel weight, TKW）、容重（test weight, TW）、籽粒产量（grain yield, GY）以及蛋白质含量（protein content, PC）。本研究采用联合方差分析（analysis of variance, ANOVA，p ≤ 0.01）与Tukey多重比较检验（p ≤ 0.01）进行数据分析。结果显示，品种与环境的交互作用对所有产量构成因子、籽粒产量及蛋白质含量均具有显著影响；氮肥管理模式与环境的交互作用则对千粒重、单位面积穗数、籽粒产量及蛋白质含量产生显著影响。研究表明，在低降水环境下，可省略氮肥追施，且不会对籽粒产量与蛋白质含量造成负面影响。在理想气象条件下，于分蘖初期追施60 kg·ha⁻¹尿素氮肥，并于孕穗期追施20 kg·ha⁻¹氮肥，可提升供试小麦品种的籽粒产量。将适宜品种匹配至理想生长环境，是实现高籽粒产量的核心前提。在帕托布兰科地区，追施氮肥的形态对小麦品种的蛋白质含量无显著影响。