Alterações espectrais, agronômicas, de desenvolvimento e crescimento do amendoim causadas por doses de cálcio e fósforo em condições de casa-de-vegetação.

Abstract

The understanding of the principles of sol fertility is essential for an efficient crop production and environmental protection. The evaluation methods of mineral nutrition of plants, in general, based on the soil analysis, plant analysis, visual diagnosis and or on the evaluation of the yield variables. In the case of the mineral nutrition of a peanut crop {Arachis hypogaea L.) most of the research work done had its responses evaluated in terms of yield variables. The objective of Shis research was to evaluate the effect of different levels of calcium and phosphorous on the leaf spectral properties, growth variables and development, production and quality of production of a peanut crop grown under greenhouse conditions. Three experiments were conducted in the greenhouse using a randomized block design. The first two experiments consisted of 20 treatments with 3 repetitions and the third experiment consisted of 15 treatments with 4 repetitions, totalizing 60 experimental units (60 pots of 22 liters each). The experiments I and 11 had a 5 x 4 factorial analysis scheme, with the factors being 5 levels of calcium (0; 300; 600; 900 and 1200 kg of CaSOi/ha) and 4 levels of phosphorous {0; 50; 100 and 150 kg of PaOs/ha) and the experiment II evaluated the residua! effect of the material of the soil of the experiment I. The third experiment had the factorial scheme of 3x5, with the factors being 3 levels of calcium £0; 300 e 600 kg oCaSO^ia and 5 levels of phosphorous (0; 50; 100; 150 and 200 k of PjO^a), The calcium and phosphorous doses were applied or? (he soil surface at the time of sowing. The resulfs of these applications were analyzed through the plant attributes (growth, development and agronomic variables), spectral properties of the leaves (reflectance, Iransmittance and absorptance), the soil chemical properties and the leaf analysis. In case of most of the growth and development variables analyzed (number of flowers, pegs, nodules, aerial phytomass and breadlh of peanul in shell), the calcium dose needed was of 600kg/ha. The best phosphorous dose presented variations, but the interval is placed between 50 and 100kg/ha. Pod and kernel weights responded well to the 300kg/ha calcium dose, The number of pods were more and the number of sterile pods were less for the 600kg/ha level of calcium, The total weight of the peanut kernels (normal kernels plus sterile kernels) did not respond well to the variations of calcium levels. The calcium content had no influence on the oil content of the peanuts. All the variables studied (except for the number of sterile pods and the oil content), responded well for the phosphorous treatment in the interval of 80 to 100kg of P2G$/ha. The oil content did not responded well to the variations in phosphorous. The residua! effects £h factor) were determined by using the agronomic, growth and development variables presented medium value of the factor h of 0,050 for calcium and 0,151 for phosphorous. In the growth analysis, the significant effect of the interaction of the levels of calcium and phosphorous were verified for the stem diameter and the leaf area and of the phosphorous doses for the height. However, the different treatments utilized did not determine substantial variations in the growth of the peanul crop. The order of absorption of ihe macronutrients, through the analysis of (he peanut leaves, were calcium, nitrogen, potassium, magnesium and phosphorous. In the case of spectral characteristics, the leaf reflectance was significantly decreased for the treatment in which the calcium level is 1200kg/ha and the phosphorous was 150kgma. These values would be the most appropriate amounts to collaborate with the nature in Ihe photosynthesis process. In general, the calcium level of 600kg/ba and phosphorous of 100kg/ha presented intermediate values of the leaf reflectance during the crop growth cycle, indicating a good stability and very characteristic phases of the evolutionary cycle of the peanut. The macronutrients of calcium and phosphorous considerably increased the peanut crop production, by increasing the number of pods. The calcium did no! exercise influence and phosphorus did not exercise beneficial effect in Ihe oil content. The study recommends the levels of 600kg/ha of calcium and 100kg/ha of phosphorous to be evaluated under the field conditions for growing the peanut crop.