Lâmina de irrigação versus cobertura do solo e manejo da fertirrigação fosfatada no cultivo do feijão-caupi

Abstract

Cowpea is a widely explored crop in northeastern Brazil, a region where the semiarid is the predominant climate. In arid and semi-arid regions, the use of irrigation is a fundamental aspect for supplying, in whole or in part, the water needs of the crops, as well as the use of plants as soil cover, to contribute to the increase in the availability of water to the crops. Another important aspect is the nutritional status, in which phosphorus plays an important role in the main components of bean bean production. The objectives were: to evaluate the effects of irrigation depths, associated with soil coverings in experiment I, as well as to measure the effects of splitting and doses of phosphorus applied via fertigation in the culture of cowpea (Vigna unguiculata L. Walp.), in experiment II. The research used cowpea cultivar, Canapu cultivar, in the edaphoclimatic conditions of Iguatu, Ceará, located in the northeastern semi-arid region, from October to December 2018. The field experiments were developed in the experimental area, belonging to the Federal Institute of Education, Science and Technology of Ceará - Campus Iguatu. In experiment I, the effects of three soil coverings and the control treatment, without soil cover (C1 - control, C2 - Crotalaria - Crotalaria juncea, C3 - Mucuna-Preta - Mucuna purpureus and C4 Guandu - Cajanus cajan) and five irrigation depths (L1 - 50%, L2 - 75%, L3 - 100%, L4 - 125% and L5 - 150% of the crop evapotranspiration). In experiment II, the effects between three phosphorus splits were evaluated, being: P1 - dose splitting in weekly applications with different percentages according to the culture absorption rate; P2 - dose split in weekly applications with equal percentage and P3 - split in two applications at 7 and 28 days after sowing, associated with five doses of phosphorus (D1 - 0, D2 - 50, D3 - 100, D4 - 150 and D5 - 200% of the recommended dose, 30 kg ha-1). In experiment I, there was a significant effect for the interaction between the irrigation blade treatments and soil cover, at a level of 1% probability by the F test for grain yield and 5% for variables: pod length and mass of one hundred grains. In experiment II, there was a significant effect between the splitting factors and phosphorus doses at a level of 1%, probability by the F test, for grain yield and 5% for pod mass. The soil cover with black mucuna was responsible for the highest grain yield (1,441.6 kg ha-1), estimated with the use of 414.9 mm, only 12% above the recommended amount of water. Phosphorus parceling with equal weekly applications (10% of the recommended dose) was responsible for the highest grain yield (1,276.74 kg ha-1), estimated for an optimal phosphorus dose of 34.82 kg ha-1, 16% higher than the recommended dose.