Macronutrient uptake and export in transgenic corn under two levels of fertilization

Abstract: The objective of this work was to evaluate macronutrient uptake and export by transgenic corn hybrids under medium and high fertilization levels. For each fertilization level, a randomized complete block design was carried out in the summer crop season, under no-tillage and supplementary irrigation, with four cultivars and four replicates. Plants were sampled throughout the entire cycle and separated into leaves, stalk, husk, cob, and grains for the determination of dry matter mass and accumulation of macronutrients in the different growth stages. Under the high fertilization level, a greater dry matter mass and nutrient uptake were observed, but grain yield was similar to that under the medium fertilization level. The uptake of N, P, Ca, Mg, and S occurs until later in the cycle of the transgenic cultivars, which also showed lower concentrations of P, K, and S in grains, when compared to older hybrids. The differential behavior of the evaluated cultivars under different fertilization levels indicates the need of updating and improving nutritional management and fertilizer recommendations for the corn crop.摘要：本研究旨在评估不同施肥水平（中、高）下转基因玉米杂交种（transgenic corn hybrids）对大量营养素（macronutrient）的吸收与携出量。试验于夏播季采用免耕（no-tillage）结合补充灌溉（supplementary irrigation）的种植模式，设置两个施肥梯度，每个梯度下均采用随机完全区组设计（randomized complete block design），供试品种共4个，试验重复4次。在作物整个生育周期内定期取样，将植株分为叶片、茎秆、苞叶、穗轴与籽粒，测定各生育阶段的干物质质量（dry matter mass）及大量营养素积累量。结果显示，高施肥水平下植株干物质质量与养分吸收量均更高，但籽粒产量（grain yield）与中施肥水平处理无显著差异。与传统老杂交种相比，供试转基因玉米杂交种的氮（N）、磷（P）、钙（Ca）、镁（Mg）与硫（S）吸收周期更长，且其籽粒中磷（P）、钾（K）与硫（S）的浓度更低。供试品种在不同施肥水平下的表现存在差异，这表明当前玉米作物的养分管理与施肥推荐方案亟需更新与完善。