É apresentado estudo da determinação de cálcio em extratos de solo por espectrofotometria de chama, utilizando o espectrofotômetro Beckman, modelo DU. A composição da chama, as pressões dos gases, as interferências e os métodos para eliminá-las foram estudados. Verificou-se ser imprescindível a eliminação das interferências causadas pelos íons de alumínio, ferro e fosfato nas concentrações que normalmente ocorrem nos solos. A utilização de EDTA a pH 9 apresentou resultados satisfatórios na eliminação dessas interferências quando em concentração 0,01 M na solução em que foi determinado o cálcio.

A study is presented on the determination of calcium in soil extracts by flame photometry, using a Beckman Model DU spectrophotometer. Flame composition, gas pressure, interferences and their elimination were studied. Results showed it to be necessary to eliminate interferences due to aluminum, iron and phosphate ions in amounts normally present in soils. Enough EDTA solution at pH 9.0 was added to the soil extract until a concentration of 0.01 M in EDTA was reached.

É estudada a absorção e acumulação de elementos minerais e a acumulação de matéria sêca em plantas de amendoim, em diversas fases do ciclo vegetativo, em condições de campo. Os resultados indicam maiores concentrações de nitrogênio e fósforo nas sementes, potássio nas hastes, cálcio na folhagem, magnésio nas hastes e fôlhas e enxôfre nas raízes. Os elementos extraídos em maiores quantidades foram: nitrogênio, potássio e cálcio. Entre o início da floração e três semanas após o início da frutificação, foi absorvida a maior parte dos nutrientes. No tratamento com adubação, cêrca de 70% do total de elementos nutritivos foi absorvido nesse período. A acumulação de 74% e 48% do total de matéria sêca, respectivamente, para os tratamentos com e sem adubação, ocorreu nesse período, evidenciando a importância da disponibilidade de nutrientes às plantas, nessa fase.

The absorption of nutrients and accumulation of substances in peanut plants at several growth stages were investigated. The studies were made on plants cultivated on "terra roxa misturada". The peanut variety Tatu was planted in non-fertilized plots and in others that received macro and micronutrients. Cultivation, spraying, and other cultural procedures were the same as those customary for commercial plantings. Plant sampling started 15 days after emergence and was then carried out at intervals until harvest. For analytical purposes the samples were divided in root, stem, leaf, fruit shell, and seed. The results obtained indicated the following pattern of nutrient accumulation in the plant: high concentrations of nitrogen and phosphorus in the seed; potassium and magnesium in the stem; calcium and magnesium in the foliage; and sulfur in the root. From the essential elements, nitrogen, potassium, and calcium were the most absorbed. The highest nutrient demand occurred in the period between early blooming and three weeks after fruit initiation. In the fertilized plots 66% to 74% of all nutrients were absorbed by the peanut plant in this period. Also, 74% and 48% of the total dry matter were accumulated in the same period in plants from plots that received fertilizers and in those from non-fertilized plots, respectively. At harvest time, the fruits accounted for 50% of the total dry weight of the plant.

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.

Estuda-se a sensibilidade das partes da fôlha (base, meio e ponta) e do tecido (porção clorofilada da lâmina e nervura), para análise das formas de nitrogênio solúvel em água (nitrato) e nitrogênio-total, como índices de nutrição de milho. As amostras de fôlhas provieram de ensaio de adubação NPK onde era visível a reação das plantas à adubação nitrogenada. A análise foliar efetuada cêrca de 9 semanas depois do plantio, fornece indicação do estado nutricional da planta, a tempo de possibilitar a correção da deficiência. Os resultados obtidos mostraram ser a base da fôlha a parte mais adequada para o estudo da nutrição nitrogenada de milho. Aí é maior a sensibilidade dos tecidos às formas de nitrogênio-total e nitrato.

A study is reported about sensitivity to total nitrogen and nitrate changes taking place in corn leaf parts (basal, median and top parts) and tissue (blades or midribs). Also a sampling procedure is described. Samples were collected from one NPK fertilizer experiment of the 3³ factorial design, the plants showing a definite response to nitrogen fertilizer. Fertilizers were supplied at the rates of 0,60 and 120 kg per hectare of each N, P2O5, and K2O. Nitrogen was supplied as ammonium sulphate; one fourth was given at planting time, the remaining topdressed when the plants were 40-50 days old. It is suggested that leaves should be sampled about 9 weeks after planting, when tassel is just emerging or a little earlier. The position of the leaf on the plant is indicated by Kuijper system, as leaf of position +4. Figure 1 shows the right position and the proper part of the leaf to be selected for analysis. Sufficient information is available to utilize the procedure outlined as a method to, diagnose nitrogen needs: A) at 60 to 70 days after planting the nitrogen absorption rate becomes more pronounced for corn plants; B) the data of chemical analysis, as obtained, gave a good indication of nitrogen status of the crop; and C) at that age it should still be possible to correct nitrogen deficiency, by adding fertilizers. The results indicated the basal, third of the leaf as the best part for diagnosing the nitrogen status, the midribs being analysed for nitrate-nitrogen and the remaining portion of the sample analysed for total nitrogen. Plants deficient in nitrogen gave low yields of grain. Mean values for NO3-N concentrations of midribs were 341 ppm for deficient plants or untreated plants, as compared with 1410 and 2119 ppm tor those receiving 60 and 120 kg N per hectare, respectively. Analysis for total N in the leaves showed mean values of 2.12, 2.79 and 3.11 per cent, respectively for the three levels of fertilizer. Thus the data indicate that nitrate-nitrogen values provide a more sensitive index of the nitrogen status of the corn plant than total N values. Phosphate fertilization had a marked influence on the levels of nitrogen in the leaves, mainly on nitrate-nitrogen content. These effects were negative, as can be seen in table 4. The greater coefficient of variation for nitrate contents also appearing in table 4 is probably due to a greater dependence of this form of nitrogen on external growth factors, such as temperature, humidity, sunlight, etc. In order to keep sampling errors to a minimum it is suggested to control closely the time of day at which samples are taken.