Absorção de nutrientes pela planta de amendoim em cultura de primavera

É apresentado estudo relativo à acumulação de matéria sêca, concentração e absorção de nutrientes em plantas de amendoim, em latossolo vermelho escuro, adubado e sem adubação. Em amostras de plantas colhidas semanalmente foram determinados os elementos: N, P, K, Ca, Mg e S. A adubação trouxe aumento de 85% no pêso sêco dos frutos e 53% no da planta. Com exceção do cálcio e do magnésio, os teores dos demais elementos foram mais elevados nas plantas adubadas. Cêrca de 80% do total de matéria sêca e de nutrientes nas plantas adubadas foram acumulados no período entre início da frutificação e início da maturação dos frutos. Nas plantas não adubadas essa acumulação representa cêrca de 60%. Êsses resultados evidenciam o período em que as plantas devem encontrar maior disponibilidade de nutrientes no solo. The dry matter accumulation and absorption as well as the accumulation of nitrogen, phosphorus, potassium, calcium, magnesium and sulfur by peanut in several growth stages under field conditions during the rainy season were investigated. The experiment was conducted at the Experimental Station "Theodureto de Camargo", in Campinas, where the soil is "dark red latosol". The seed variety used was "Tatu", and treatments comprised plots with and without fertilizer. The fertilizer treatment included micronutrients. The cultivation and insect and fungi control were those customary in large plantations. Plant sampling started 15 days after the emergence of the plants,, and from then on, once every week, until cropping time. For analytical purposes, the samples were divided into root, stem, leaf, and the fruit into shell and seed. The results showed definite patterns of accumulation of nutrients in the plant, as follows: nitrogen and phosphorus in the seed, sulfur in the root and potassium, calcium and magnesium in the stem and foliage. From the supplied elements, nitrogen, potassium and calcium were the most absorbed. The highest nutrient demand occurred in the period between early frutification and beginning of leaf shedding, three weeks before the cropping. In this period were accumulated about 80% and 60% from the total dry matter and total nutrients, respectively. At cropping time the fruit dry weight was greater than the vegetative part.