Produção de grãos verdes de feijão-caupi fertirrigado por gotejamento contínuo e pulsado

Abstract

Cowpea (Vigna Unguiculata L. Walp.) is a legume cultivated throughout the national territory, especially in the North and Northeast regions of Brazil. However, these regions still have low production rates, due to water limitations and little investment in technologies that contribute to the improvement of production. Thus, the objective of this work was to evaluate the effect of the use of conventional fertilization and fertigation blades applied by continuous and pulsed drip on the production of green grains, accumulation and export of nutrients by the cowpea crop. The treatments were arranged in a 5x2+2 factorial scheme, with five irrigation depths equivalent to 40, 60, 80, 100 and 120% of crop evapotranspiration (ETc), combined with two types of fertigation application (pulsed and continuous), plus two additional treatments (conventional fertilization irrigated by pulse and continuously). Additional treatments were irrigated with a water depth of 100% ETc. A randomized block design with four replications was adopted. For the evaluation of cowpea production, the variables analyzed were number of pods, number of grains, fresh and dry mass of pods, fresh and dry mass of grains, fresh and dry mass of the shoot. Regarding the accumulation and export of nutrients by cowpea, the variables nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), manganese (Mn) were analyzed. , copper (Cu), zinc (Zn) and iron (Fe). The fertigation depths between 80 and 100% of ETc were the ones that provided the best productive performance of cowpea. Plants irrigated with 100% ETc water depth and conventionally fertilized showed higher yields when the water depth was applied pulsed. The decreasing order of total nutrient accumulation by cowpea crop, for both types of fertigation application and for control 1 management was: N > K > Ca > P > Mg > S > Fe > Mn > Zn > Cu, for witness 2 it was: N > Ca > K > P > Mg > S > Fe > Mn > Zn > Cu. The decreasing order of nutrient export by cowpea pods and grains for pulse fertigation application was: N > P > Ca > K > Mg > S > Fe > Zn > Mn > Cu. The application of continuous fertigation presented the following order: N > P > Ca > Mg > S > K > Fe > Zn > Mn > Cu. For witness 1 the descending order was: N > P > Ca > K > Mg > S > Fe > Zn > Mn > Cu and the descending order of export for witness 2 was: N > Ca > K > P > Mg > S > Fe > Zn > Mn > Cu.