Modern High-Yielding Maize, Wheat and Soybean Cultivars in Response to Gypsum and Lime Application on No-Till Oxisol

ABSTRACT Modern maize, wheat, and soybean cultivars are usually characterized by a short cycle, high shoot-root ratio, and high responsiveness to nutrient input. Continuous no-tillage management (NTS) frequently leads to a steep gradient in soil chemical quality with depth, thus decreasing yield under conditions of acid subsoil and water stress. This study aimed to evaluate the effect of gypsum, applied separately or in combination with lime, on the yield of cultivars used in the state of Rio Grande do Sul, Brazil. The study consisted of four experiments conducted on a typic Hapludox under NTS. The experiment was arranged in a randomized block design with three replications. Experiments I and II were carried out on soils with a satisfactory chemical soil quality and tested treatments of gypsum applications ranging from 0.0 to 6.5 Mg ha-1. The other experiments were carried out on acid soil (experiment III) and a soil with an abrupt drop in chemical quality (experiment IV). Experiment III was arranged in a split plot design, where plots corresponded to gypsum rates between 0.0 and 5.0 Mg ha-1, and subplots to two lime rates (0.0 and 2.0 Mg ha-1). Experiment IV was conducted in a split plot design, with plots consisting of gypsum rates from 0.0 to 6.0 Mg ha-1 and subplots of lime rates from 0.0 to 4.8 Mg ha-1. Of a set of 17 harvests investigated during the experimental period, 82 % responded with yield increases to gypsum and lime inputs. The gypsum rate that induced the highest grain yield was high (4.7 Mg ha-1) and similarly, the maximum technical efficiency of lime was higher than the currently recommended. Furthermore, the combined application of lime and gypsum increased yield. There was a correlation between grain yield with the chemical quality of the soil layer 0.25-0.40 m in experiment I, 0.00-0.40 m in experiment II, and the 0.00-0.25 m in experiment IV. Only in experiment III, where the surface layer was acidic, the diagnostic layer usually sampled (0.00-0.10 m) was correlated with grain yield. Therefore, the use of the 0.00-0.25 m soil layer with critical base saturation values of 65 % and maximum Al saturation of 5 % could improve the current recommendations for soil correction. To exploit the yield potential of modern grain cultivars on dystrophic Oxisol, the formation of a thicker layer with high chemical quality is an efficient strategy.

摘要：现代玉米、小麦与大豆栽培品种通常具有生育期短、地上部-地下部生物量比高且对养分投入响应性强的特点。免耕连作管理（No-tillage System, NTS）常导致土壤化学性质随土层深度呈现急剧梯度变化，进而在酸性亚耕层与水分胁迫条件下降低作物产量。本研究旨在评估分别施用或与石灰配施的石膏，对巴西南里奥格兰德州主推栽培品种产量的影响。本研究在免耕连作管理下的典型简育湿润铁铝土（typic Hapludox）上设置了4组田间试验，均采用随机区组设计并设置3次重复。试验I与试验II在土壤化学性质优良的田块开展，设置的石膏施用量梯度为0.0~6.5 Mg·ha⁻¹；其余两组试验分别在酸性土壤（试验III）与化学性质骤降的土壤（试验IV）上进行。试验III采用裂区设计，主区为石膏施用量（0.0~5.0 Mg·ha⁻¹），副区为2个石灰施用量水平（0.0与2.0 Mg·ha⁻¹）；试验IV同样采用裂区设计，主区石膏施用量范围为0.0~6.0 Mg·ha⁻¹，副区石灰施用量梯度为0.0~4.8 Mg·ha⁻¹。试验周期内共调查17次收获结果，其中82%的处理在施用石膏与石灰后实现了产量提升。实现最高籽粒产量的石膏施用量为4.7 Mg·ha⁻¹，与之类似，石灰的最佳技术施用量也高于当前行业推荐标准。此外，石灰与石膏配施可进一步提升作物产量。试验I中籽粒产量与0.25~0.40 m土层的土壤化学性质呈显著相关，试验II中相关土层为0.00~0.40 m，试验IV中则为0.00~0.25 m。仅在试验III（表层土壤呈酸性）中，常规采样的诊断土层（0.00~0.10 m）与籽粒产量存在相关性。综上，以0.00~0.25 m土层为研究对象，设定临界盐基饱和度为65%、最大铝饱和度为5%，可优化当前土壤改良推荐方案。若要在贫瘠铁铝土上挖掘现代谷物栽培品种的产量潜力，构建化学性质优良的厚土层是一项高效策略。