Foliar application of molybdenum on cover crops and response of common beans in successive cultivation

ABSTRACT The effects of foliar application of Mo and use of N from cover crops (Crotalaria juncea L. and Canavalia ensiformis (L.) DC) on the performance of common beans were investigated in this study. Field experiments were carried out in a succession planting system (cover crops - common beans), and nitrate reductase activities were evaluated in the laboratory. The production of cover crops was done in a 2 x 4 factorial scheme installed in random blocks with four replications. The two cover crops sunn hemp and jack bean composed the first factor and the molibdenum doses (0, 40, 80, and 120 g ha-1) the second. These doses were applied as foliar fertilization using sodium molybdate (Na2MoO4) as Mo source. For bean cultivation, an unfertilized control treatment was evaluated.. Sunn hemp showed a linear positive response to Mo application in terms of shoot dry matter and N accumulation, while jack bean showed a quadratic negative response for shoot dry matter; for N accumulation, there was no adjustment of the regression models. Nitrate reductase activity in the common beans was up to three times higher at the Mo dose of 0 g ha-1 when compared to the treatments with Mo application to both cover crops. Cover crops or Mo doses had no significant effect on bean productivity.

摘要 本研究探究了叶面施用钼（Mo）以及以覆盖作物（猪屎豆*Crotalaria juncea* L.和刀豆*Canavalia ensiformis* (L.) DC）为氮源对普通菜豆生长表现的影响。试验采用“覆盖作物-普通菜豆”连作种植体系开展田间试验，并在实验室测定了硝酸还原酶活性。覆盖作物种植试验采用2×4析因设计，设置4次重复的随机区组试验。第一因子为两种覆盖作物：太阳麻（sunn hemp）与刀豆；第二因子为钼肥施用量：0、40、80、120 g·ha⁻¹。供试钼源为钼酸钠（Na₂MoO₄），通过叶面施肥方式施用。菜豆栽培设置无肥对照处理。结果显示，太阳麻的地上部干物质积累量与氮素累积量均随钼肥施用量增加呈线性正响应；刀豆的地上部干物质积累量则随钼肥施用量增加呈二次负响应，但其氮素累积量未拟合出有效回归模型。与对两种覆盖作物施用钼肥的处理相比，钼肥施用量为0 g·ha⁻¹时，普通菜豆的硝酸还原酶活性最高可达3倍。覆盖作物种类与钼肥施用量均对菜豆产量无显著影响。