Respostas de plantas de feijão-de-corda à aplicação de biofertilizantes via foliar, sob condições de baixa e alta salinidade

Abstract

Faced with the need to seek higher yields and lower costs in saline areas, the use of organic fertilizers has been widely used in agriculture, as is the case of bovine biofertilizer, but studies show that its use as a minority of the adverse effects of salinity, has been little studied. The objective of this study was to evaluate the responses of cowpea to foliar application of biofertilizer under salinity conditions. The survey was conducted at the experimental farm Vale of Curu, at Pentecoste, Ceará, from november 2010 to january 2011. The plants were arranged in a split plot arrangement in a randomized block design with four blocks. The plot consisted of four different concentrations of salts in irrigation water via drip (0.5, 2.2, 3.6 and 5.0 dS m-1) and the subplots consisted of four levels of biofertilizers, corresponding to 0 , 15, 30 and 45% of the volume applied. The irrigation with saline water was dripping through and salts used to prepare the treatments were: NaCl, CaCl 2 .2H 2 O, MgCl 2 .6H 2 O in the proportion 7:2:1. In biofertilizer preparation was used fresh cattle manure and water in proportion (1:1). The doses of biofertilizers were applied weekly until the beginning of flowering. During the experiment were made manual weeding to control weeds and application of pesticides to control pathogens. In conducting the experiment were checked gas exchange, vegetative growth and assessed at the end of the pods were collected to assess productivity. Salinity influenced gas exchange (photosynthesis, stomatal conductance and internal CO 2 concentration), growth (dry matter and total), production (grain weight and yield) and nutrients (K / Na), without influence in other levels of minerals, nor the accumulation of salts in the soil. The influence of low salinity in the variables occurred due to high levels of rainfall (233.0 mm) during the experiment. Generally no significant effect was observed in the foliar application of biofertilizer, showing that application does not lessen the effect of saline irrigation. Due to the low influence of the biofertilizer the salinity of the water, it can be stated that the application can not be recommended for cultivation, requiring more studies, both in the form of application, as in proportion to be applied.