Mudanças nas frações lábeis de fósforo no solo em função da aplicação de fertilizantes minerais e organominerais fosfatados.

A produção de fertilizantes organominerais a partir resíduos orgânicos como, por exemplo, a cama de frango tem se tornado uma prática comum, visto os benefícios econômicos e ambientais. O uso de fertilizantes organominerais pode alterar a dinâmica das formas de fósforo (P), visto a sua natureza física e química. No entanto, estudos sobre o tema ainda são incipientes. Dessa forma, objetivou-se com esse estudo avaliar as frações lábeis de P no solo sob aplicação de fertilizante organomineral comparado a uma fonte mineral em doses crescentes de P (0, 125, 250, 375 e 500 mg por vaso). As frações lábeis de P no solo aumentaram significativamente com as doses de P, contudo, não houve diferenças entre os fertilizantes (exceto, na dose de P de 375 mg por vaso). Esse estudo traz informações relevantes acerca das transformações de P no solo permitindo aperfeiçoar e fomentar o uso de fertilizantes organominerais fosfatados

Effects of molybdenum, nickel, and nitrogen sources on the mineral nutrition and growth of rice plants.

The aims of the current work were to measure the effect of Mo and Ni on dry-matter yield of rice plants supplied with two N sources (ammonium nitrate and urea) and to evaluate the influence of Mo and Ni on variables related to dry-matter yield, such as activity of both urease and nitrate reductase, chlorophyll, net photosynthesis rate, total N, nitrate content, and Mo and Ni concentrations in roots and shoots

Nitrogen metabolism in coffee plants in response to nitrogen supply by fertigation.

Coffee plants require high application rates of nitrogen (N) to produce coffee beans. However, information regarding plant N uptake and assimilation under intensive high-technology cultivation systems is scarce, a situation which restrains the maximizing productivity with minimal N rates. The aim of this study was to evaluate N assimilation enzymes such as nitrate reductase (EC 1.6.6.1), glutamine synthetase (EC 6.3.1.2), urease (EC 3.5.1.5), and N compounds of coffee plants during a phenological cycle in response to N applied by fertigation. Our study was carried out with 7-year-old trees of Coffea arabica L., under a center pivot sprinkler irrigation and fertigation system, with five N rates (0, 200, 400, 600, and 800 kg ha−1) applied to the coffee field. The results of the present study suggest that both N metabolism enzymes, and the content of nitrate and ammonium in coffee were directly related to the phenological cycle. The N fertigation rates are correlated with the N and amino acid contente. Nitrate reductase and urease showed higher activities before anthesis and during grain filling. Glutamine synthetase showed highest activities during rapid grain expansion. The data also indicate that there is merit in gaining greater understanding of N metabolism in coffee plants grown under high-intensive systems. There is therefore merit in conducting further research on how monitoring the N assimilation enzymes might be used to improve fertilizer management of coffee in commercial orchards

A poultry litter-derived organomineral phosphate fertilizer has higher agronomic effectiveness than conventional phosphate fertilizer applied to field-grown maize and soybean.

Inadequate disposal of poultry litter (PL) may promote eutrophication of water bodies due to its high nutrient content, including phosphorus (P). Thus, recycling P from PL to produce organomineral fertilizer (OMF), reduces the dependence on finite mineral P reserves, and also reduces P losses from soil. In this context, a field experiment was carried out to assess the agronomic effectiveness of a granular PL-derived OMF applied to maize and soybean in a highly weathered tropical soil. OMF was compared to single superphosphate (SSP) at five P rates between 0 and 70 kg ha-1. The shoot dry weight (SDW) and grain yields of soybean and maize were affected by P rates; however, no difference between OMF and SSP was found. A similar trend was observed for soil P and P uptake. The leaf P content and soil pH were not affected by either P sources or P rates. Although there was no difference between OMF and SSP on the crop yields, OMF had the highest relative agronomic effectiveness based on the SDW. These results show that the production of granular OMF from PL is a viable alternative to conventional P fertilizers and reduces the dependence of mineral P reserves