Phosphorus in alkaline soils of the semiarid region, Brazil: inorganic fractions, capacity factor, and availability.

The study was designed to quantify the contents of Pi fractions and correlate them with the P capacity factor of soils in the Brazilian semiarid region. We also evaluated the effect of soil P doses contact time and P availability for maize plants in alkaline soils of the Brazilian semiarid region. Soil samples were collected between the Piranhas-Açu (RN) and Jaguaribe (CE) rivers valleys. The maximum phosphate sorption capacity was highly correlated with the values of remaining P, indicating that it can be used as a measure to estimate the P capacity factor of these soils. Maximum P sorption capacity correlated with Fe2O3 and Ca2+ contents and pH values. These results demonstrate that P sorption is explained by P adsorption on the surface of iron oxides and by its precipitation with Ca2+ in alkaline soils. The contact time increases promote plant P contents decreased substantially in the first 30 to 60 days after fertilization and decreased until 120 days of incubation but then tended to stabilize at the longest soil P contact times.

The clay content and P-remnant estimate the P capacity factor in alkaline soils.In alkaline soils, there is a predominance of P­Ca and P­Fe.The availability of P stabilizes after 120 days.The largest corn biomass occurs between the P doses of 256­288 mg dm⁻³.

Acúmulo de matéria seca, absorção e exportação de micronutrientes em variedades de bananeira sob irrigação / Accumulation of dry matter, absorption and exportation of micronutrients in banana (Musa spp. ) varieties under irrigation

Para estimativa da demanda de micronutrientes pela bananeira (Musa spp.) é fundamental que se conheçam as quantidades de matéria seca e de micronutrientes acumuladas na planta e exportadas pelo cacho. Neste trabalho, objetivou-se avaliar o acúmulo de matéria seca e de micronutrientes em seis variedades de bananeira sob irrigação. Foram amostradas plantas das variedades Grande Naine, Pacovan, Pacovan-Apodi, Prata-Anã, Terrinha e Gross Michel. As variedades foram plantadas em fileiras duplas, sendo 1.666 covas por hectare. Na época da colheita, foram escolhidas quatro touceiras de plantas de cada variedade para amostragem da planta-mãe, que foi dividida em rizoma, pseudocaule, pecíolo, limbo, engaço e frutos. Foram feitas pesagens para a determinação da matéria fresca de cada parte da planta-mãe de uma mesma touceira e retirada uma amostra de aproximadamente 700 g dessas partes para determinação do acúmulo de matéria seca e dos teores de micronutrientes. As amostras foram lavadas rapidamente com água de torneira, depois com água destilada e colocadas sobre as bancadas de uma casa de vegetação para pré-secagem. Posteriormente, foram colocadas em sacos de papel e levadas para uma estufa de circulação forçada de ar para obtenção do acúmulo de matéria seca e determinação dos teores de B, Cu, Fe, Mn e Zn. As variedades Pacovan, Prata Anã e Pacovan-Apodi acumularam maiores quantidades de matéria seca e de micronutrientes, quando comparadas com as variedades Grande Naine, Gross Michel e Terrinha, sendo a seguinte ordem decrescente de acúmulo e de exportação de micronutrientes: Mn > Fe > B > Zn > Cu.

To estimate the demand of micronutrients for the banana plants (Musa spp.), it is essential to know the amounts of dry matter and micronutrients accumulated in the plant and exported by the bunch. The objective of this study was to evaluate the accumulation of dry matter and micronutrients by six banana varieties under irrigation. Plants of Grande Naine, Pacovan, Pacovan-Apodi, Prata-Anã, Terrinha and Gross Michel varieties grown in double rows, with a density equivalent to 1,666 plants per hectare were sampled. At harvest four plants of each variety were selected for sampling of mother-plant, which was divided into rhizome, pseudostem, petiole, leaf blade, stalk and fruits. The plant parts were weighed to determine the fresh weight of each part and a sample of about 700 g of each part was collected to determine dry weight and contents of micronutrients. The samples were washed quickly with tap water and later with distilled water and placed in a greenhouse for pre-drying and afterwards conditioned in paper bags were put in an oven of forced circulation of air for obtaining the dry matter and subsequent determination of the contents of B, Cu, Fe, Mn and Zn. The varieties Pacovan, Prata Anã e Pacovan Apodi accumulated greater amounts of dry matter and micronutrients, when compared to the varieties Grande Naine, Gross Michel e Terrinha, observing the following decreasing order of accumulation and export of micronutrients: Mn > Fe > B > Zn > Cu.

Acúmulo, exportação e restituição de nutrientes pelas bananeiras "Prata Anã" e "Grand Naine" / Accumulation, export and restitution of nutrients by 'Prata Anã' and 'Grand Naine' bananas

Conhecer o estado nutricional da parte colhida das plantas é importante para se analisar a qualidade do produto e a remoção de nutrientes da área de cultivo. Com tal objetivo, realizou-se este trabalho, visando-se avaliar os nutrientes exportados (engaço + frutos) e os restituídos ao solo de um bananal, no primeiro ciclo de produção. A pesquisa foi realizada entre junho/2004 e maio/2005 em um Cambissolo, em Limoeiro do Norte-CE, onde foram plantados dois blocos de amostragens com as cultivares "Grand Naine" e "Prata Anã". A partir do 30o dia após plantio e a cada 45 dias, foram amostradas e separadas, em suas diversas partes, as plantas de quatro touceiras, escolhidas aleatoriamente, para análise. A exportação de nutrientes pelo cacho da cultivar "Prata Anã" foi em ordem K>N>Ca>P>Mg, enquanto para a cultivar "Grand Naine" a seqüência foi K>Ca>N > P>Mg. Por ocasião da colheita, na touceira da "Prata Anã", foram acumulados, em média, 2,2 vezes mais nutrientes, comparada com a planta mãe, enquanto na "Grand Naine" essa relação, em média, foi de 1,2. Independente da cultivar, a ordem decrescente da quantidade de nutrientes restituídos ao solo foi K>Ca>N>Mg>P.

The knowledge about the content of nutrients in the harvested part of plants is important to assess the quality of product and the removal of the nutrients from the cultivated area. This research was carried out to evaluate the nutrients exported (rachis of the inflorescence + fruits), and restituted to the soil, in a banana plantation. The study was conducted during the period of June, 2004 to May, 2005, in an Inceptisol, in the municipality of Limoeiro do Norte, Ceará, where two blocks of samplings were planted with 'Grand Naine' and 'Prata Anã' cultivars. Starting from the 30 days after planting, at 45 days interval, plant samples were collected, harvesting four clumps in full competition, chosen at random for analysis. The sequence of nutrients exported by the bunch in case of 'Prata Anã' was K>N>Ca>P>Mg while in Grand Naine cultivar the sequence was of K>Ca>N>P>Mg. At harvest time, in the clumps of cv. Prata Anã were accumulated on an average 2.2 times more nutrients in comparison to mother plant while in the plants of Grand Naine such relation was 1.2 times. Independent of cultivar, the order of the amount of nutrients returned to the soil after the crop removal was K>Ca>N>Mg>P.