Doses of Crotalaria juncea: Residual effect on zucchini and maize crop in sequence to broccoli ¹

Doses de Crotalaria juncea: Efeito residual no cultivo de abobrinha e milho em sequência ao brócolis

ABSTRACT

Amounts of N from green manures not absorbed in the first cycle can be absorbed by the subsequent crops. Therefore, it is important to quantify and monitor the residual effects of green manure to increase the agronomic benefits of its use in cropping systems. Our purpose was to study the residual effect of doses of the Crotalaria juncea green manure applied in broccoli crop in the zucchini-maize succession. This study was carried out in a crop succession system organized in three crops, with seven treatments and four major doses of green manure as 0, 3, 6, and 9 t ha^-1. The control treatments consisted of a mineral fertilization, a treatment with 25 t ha^-1 compost, and another as absolute control without organic compost or mineral fertilizer. The experimental plot consisted of five rows spaced 0.8 m with 3 m in length. The experimental design was a completely randomized block with four replications in a split-plot scheme in time for growth with variables of adjustment of statistical models by the response surface methodology. With the highest dose of green manure, the yield of zucchini plants was greater than the yield with 25 t ha^-1 compost control and similar with mineral fertilizer. As for the maize yield in the dose of 9 t ha^-1 green manure, the yield was superior only to absolute control. There was a residual effect of C. juncea mass, which was applied in broccoli crop for growth and yield of zucchini and maize grown in succession. The residual effect is dependent on the amount of weight of C. juncea applied, with the greatest effects in larger doses.

Key words:
Brassica oleracea var. italica; Cucurbita pepo; Zea mays; succeeding crops; green manure; nitrogen.