In the process of phosphate rock acidulation, several impure P compounds may be formed along with the desirable Ca and NH4 phosphates. Such compounds normally reduce the content of water-soluble P and thus the agronomic effectiveness of commercial fertilizers. In order to study this problem, a greenhouse experiment consisting of three consecutive corn crops was conducted in samples of a Red-Yellow Latosol (Typical Hapludox) in a completely randomized design (6 x 2 x 2), with four replicates. Six commercial fertilizers […]

The use of legume cover crops contributes to soil conservation and would be an economical N source to maize. Since only winter legumes were evaluated in southern Brazil, this study was carried out to assess the effect of four intercropped summer species (Canavalia ensiformis, Cajanus cajan, Stizolobium niveum and Glycine sp.) on N supply and maize yield increase, in comparison with a control treatment, without legume cover crops. Cropping system effects on maize crop were evaluated under three mineral N […]

Legumes cover-crops represent a good alternative to supply N as well as to improve yield of commercial crops. The acceptance of this technique by growers and extension agents, however, depends on its economical advantage in relation to traditional systems. In this study, the effect of four summer legumes cover-crops (Canavalia ensiformis, Cajanus cajan, Stizolobium niveum and Glycine sp), was evaluated in association with three N rates (0, 60 and 120 kg ha-1), on the net income of corn. Two medium-term […]

A long-term field trial was carried-out in Jaboticabal (SP) to estimate the effect of production systems on soil nitrogen and soil organic matter fractions. The treatments tested were corn in conventional sowing in summer and no tillage in winter (C-Mi-P), maize in direct sowing in summer and no tillage in winter (D-Mi-P), maize in direct sowing in summer, Mucuna aterrina as green manure in winter (D-Mi-Mu), maize in direct sowing in summer, Cajanus cajan as green manure in winter (D-Mi-Gu), […]

In order to evaluate the viability of corn planting in a soil under reduced tillage, a field trial was conducted in Passo Fundo (Rio Grande do Sul, Brazil), in December, 1988. In the control plots, soil tillage consisted of chisel plowing and disking. In the other five treatments, tillage was done through a conjugated operation (chisel plow with a clod break roller). In the control and in one of the other treatments, the configuration of each line of the planter-fertilizer […]

This work was undertaken at the State University of North Fluminense (UENF), State of Rio de Janeiro, Brazil, under greenhouse conditions, in the first semester of 1996, to evaluate the role of arbuscular mycorrhizal fungi (AMF) in the process of nitrogen transfer from bean to maize plants using the isotope 15N. Special pots divided in three sections (A, B and C), were constructed and either no barrier and a nylon mesh screen (40 ∝m) (which allowed the AMF hyphae to […]

Phosphorus availability in samples of Aquatibia (Typic xerofluvent) and Hoda (Ultic haploxeralf) soils incubated with increasing amounts of organic materials (barley straw, cowpea plant tops, dairy manure and sewage sludge) was estimated by different chemical methods and by measuring the activity of the enzymes acid phosphatase and phosphodiesterase, at the Department of Soils and Environmental Sciences of the University of California/Riverside, from January to November of 1985. In a greenhouse study, yield of dry matter and P uptake by corn […]