Efeitos da fertirrigaÃÃo com efluente de lagoa de polimento nos atributos do solo e na produÃÃo de feijÃo caupi (Vigna unguiculata (L.) Walp)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

This work aimed to investigate, through an experiment under field conditions, the chemical and physico-hydrical alterations of a typical Argissolo Amarelo EutrÃfico, and the production components of the cowpea bean (Vigna unguiculata (L.) Walp), in response to the fertigation management with secondary effluent (ME) originated from domestic source, comparing the results with those obtained with potable water (MA), in drainage lysimeters. The monitored physical and chemical characteristics of the soil were: pH, Organic Matter, P, K, Na, Ca+2, Mg+2, Fe, Cu, Zn, Mn, ESP, SAR, soil density , particle density , volumetric water content and soil penetration resistance. In the bean crop at the end of the cycle the following production components were evaluated: pods per plant, grains per pod, weight of 1000 seeds, total dry matter and yield. At the end of the experiment, it was verified that the type of water quality (effluent and potable water) used in the irrigation, considering the possible soil salinization problem, the results showed that the potable water did not present âany restrictionâ of use during the months corresponding to the first and second planting. However, the effluent showed restrictions from âslight to moderateâ during the same periods. In regards to the risks of reduction in the infiltration rate into the soil , both the potable water and the effluent showed a âsevere restrictionâ degree at the beginning of the first planting ( October) ; in the remainder of the crop cycle, went from âlight to moderateâ and âsevereâ respectively. In the second planting the potable water showed restrictions were âlight to moderateâ, while the effluent showed âno restrictionsâ. The low SAR values due to the Ca+2 and Mg+2 concentrations, indicate that, both the potable water and the effluent can be managed without compromising the soil. As to the specific toxicity, the restriction degrees of âlight to moderateâ and ânoneâ were attributed, in most of the plantings, both for the water and the effluent. In reference to the Na+, it was verified that this elementâs concentration was, on the average, superior in the first phase of planting. The average pH in the water and in the effluent was considered normal for irrigated use. The average oligoelements concentrations are in conformity with the directives for irrigation use for long term periods. The application of secondary effluent was effective in the supply of water demand of bean and, due to its chemical composition, made it possible to increase soil fertility and macronutrients offer. The accumulated depth in the two periods supplied the N demand. In relation to the micronutrients (Fe, Cu, Zn, and Mn), the depths applied did not supply the soil requirements, due to the low availabilities of Fe, Cu, and Mn. The management with effluent ME was more effective in raising the soil pH than the MA in most of the depths monitored. It was observed that the ME was more effective in the increase of the Organic Mater content (OM) than the treatments that received MA. In reference to the exchangeable P content, generally it was possible to verify that the ME was more effective in increasing the available soil P content than the treatments with MA. There was an increase in the available Potassium (K+) in the soil in response to the adoption of the two managements with the effect been more pronounced in the MA. The adoption of the ME decreased the exchangeable Na+ in the soil at the depths of 0,0- 0,40 m, a fact derived from the addition of Ca2+ and Mg2+ , through the application of calcarium and simple super phosphate ( which contains from 18 to 20% of Ca+2) . The rains occurring during the vegetative cycle and at the end of the cropping, also contributed to the decrease in Na+ at the specified depths. The increase in the exchangeable calcium (Ca2+) content in the soil was more effective with the adoption of the ME than the MC, in most of the experiments with ME. The increase in exchangeable magnesium (Mg2+) in the soil occurred in a more expressive form in the ME, showing that the application of effluent can be an alternative to add Mg2+ to the soil. The results referring to the Exchangeable Sodium Percentage (ESP) showed that, generally, the treatments managed with water (MA) showed higher ESP values than those treated with the effluent. The adoption of the MA was more efficient in the increase of the SAR than that managed with ME. The increase in the soil RAS, verified in both managements , was attributed to the increase in concentration of Na+ in relation to the increase in Ca2+ and Mg2+. In respect to the soil micronutrients, it was seen that the Fe and Cu concentrations, sometimes increased and other times decreased. The Zn concentration increased while that of Mn decreased. The soil bulk and particle densities were not influenced by the ME and MA management, however, the depth discreetly influenced the total soil porosity. The soil penetration resistance was more effective in the ME than the MA, resulting in lower values of resistance. In the production components the T2 (E+ NPK) treatment showed higher yield. The T1 treatment (E) presented an yield 15% lower than the T6 (A+NPK) treatment, indicating that the use of effluent can be an economic option where the unavailability of some soil nutrients can be corrected with the offer of the nutrients available in the effluent

ASSUNTO(S)

engenharia civil cowpea bean irrigation secondary effluent feijÃo caupi reuse efluente domÃstico irrigaÃÃo drainage lysimeters lisÃmetro de drenagem reÃso

ACESSO AO ARTIGO

Documentos Relacionados