ABSTRACT

The experiments were conducted to verify the effect of doses and application time of boron (B) in the grain yield of maize and to study different plant tissues as a nutritional diagnosis tool for B. Six doses of B (0, 1, 2, 3, 4 and 12 kg ha⁻¹) and two application times (before at sowing and V6 growth stage) were tested. In the first growing season, the B doses and application time did not influence yield components of maize. While the second growing season, B application reached maximum grain yield with 5.0 kg ha⁻¹ at sowing, but at a high dose provided toxicity causing injuries in the cobs. In general, the B content in the leaf at flowering stage was higher with the application at V6 growth stage. B content and distribution in the leaves close to the cob vary with the rainfall that occurs before to the collection, harming the definition of the critical leaf level. The B content in the silk can be a reliable alternative for checking the deficiency or toxicity of this nutrient in the plant, presenting critical level for deficiency (calculated) of 23.2 mg kg⁻¹ while values above 31.5 mg kg⁻¹ can be considered toxic.

摘要

进行实验以验证硼 (B) 的剂量和施用时间对玉米籽粒产量的影响，并研究不同的植物组织作为 B 的营养诊断工具。 六种剂量的 B (0, 1, 2, 3 、 4 和 12 kg ha ^-1 ) 和两次施用时间（播种前和 V6 生长阶段）进行了测试。在第一个生长季，B 剂量和施用时间不影响玉米的产量构成。在第二个生长季节，B 施用达到最大谷物产量，达到 5.0 kg ha ^-1在播种时，但在高剂量时会产生毒性，导致玉米棒受伤。总体而言，开花期叶片中B含量较高，V6生育期施肥。靠近穗轴的叶子中 B 的含量和分布随收集前发生的降雨而变化，从而损害了临界叶子水平的定义。蚕丝中的 B 含量可以作为检查植物中该营养素缺乏或毒性的可靠替代方法，其缺乏（计算）的临界水平为 23.2 mg kg ^-1而高于 31.5 mg kg ^{-1 的}值可被认为是有毒的.