Fertirrigação do tomateiro (Solanum lycopersicum) sob manejo orgânico, utilizando água residuária de bovinocultura de leite

Abstract

The use of wastewater in fertigation of crops promotes increased productivity and product quality, and also contributes to the reduction of environmental pollution and production costs. The aim of this study was to evaluate the effects of fertigation using wastewater from dairy cattle on the growth of tomato under organic management. The two experiments were conducted in the State Center for Research in Organic Agriculture (PESAGRO-Rio) in different seasons: in the periods between October 2011 and February 2012 (spring-summer) and between May and September 2012 (autumn-winter).The treatments were constituted by six doses of nitrogen based on the recommendation for tomato (100 kg ha-1), through fertigation with organic wastewater from dairy cattle (ARB) (0%, 50%, 75%, 100%, 125% and 150%) and (0%, 50%, 100%, 200%, 300% and 400%), respectively for the tests in spring-summer and autumn-winter. ARB blades have been determined considering nitrogen as reference nutrient. In the first trial were evaluated plant growth (diameter of the stem above the soil surface and branch length) at three different dates; fruit yield per plant per week, from the beginning of harvest’s phase to the end of the trial period; accumulated productivity throughout the culture cycle; health of fruits obtained with respect to the presence of fecal coliform and salmonella; and classification of all fruits harvested on the range coloring and with respect to the mean diameters (longitudinal and equatorial). In the second trial, were evaluated: plant growth (stem diameter above the soil surface and length of branches) in five dates; fruit yield per plant per week, from the start of harvest’s phase to the end of the trial period; productivity accumulated throughout the culture cycle; classification of fruits harvested only in the fourth stage, with respect to the staining band and mean diameters (longitudinal and equatorial); and the nutritional content in leaves, in order to evaluate the effects of irrigation with ARB on tomato. Data obtained were submitted to analysis of variance and regression analysis, as well as the treatment means were estimated and comparison between them was performed by the probability of the difference, using the "t" test of "Student" and assuming a probability level of 5% for all tests.There was no significant effect of doses of ARB in any of the parameters evaluated in the first trial and, for all the doses, harvested fruits were classified as commercial and presented a mean size (transverse diameter between 25 and 30 mm), as well as no contamination of fruit by coliforms and Salmonella was observed. In the second trial, also has been found no significant effect of doses of ARB on crop growth parameters (diameter and length of the branches); there was a linear increasing effect on production per harvest and accumulated productivity, with maximum values found for treatment with 400% of the nitrogen recommended culture; in relation to the nutrient content in leaves, nitrogen, phosphorus and potassium differ among treatments, presenting increasing linear effect of accumulation of nutrients in the leaves as a function of the ARB applied dose and maximum values obtained for the dose of 400% nitrogen; the other nutrients evaluated proved suitable for the crop development. The conclusion was that the nitrogen in organic cultivation of tomato can be achieved through fertigation with ARB and must be supplemented to provide the appropriate amount of phosphorus and potassium.