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Nitrogen (N) and phosphorus (P) deficiency is one of the important causes of degradation of cultivated pasture under tropical conditions. The aim of this study was to evaluate phosphate rates and sources, and N rates on the concentration and uptake of N and P, and shoot dry mass (SDM) yield of Megathyrsus maximum grass cv Mombasa in an Ultisol. The trial was carried out in a greenhouse in pots with 4.0 dm −3 of soil. The experiment was arranged in a completely randomized design with four replicates. The 3 × 3 × 3 factorial treatments consisted of phosphorus sources [reactive rock phosphate from Morocco (RPM), reactive rock phosphate from Algeria (RPA) and triple superphosphate (TSP)], three phosphorus rates (0, 150, and 300 mg kg −1), and three N rates (0, 250, and 500 mg kg −1). The SDM and tillering of Mombasa grass were significantly influenced with the TSP, RPM, and RPA application associated with N fertilization. The RPM, RPA, and TSP met the nutritional demands of Mombasa grass. The three P sources showed the same effect on the total N uptake by Mombasa grass. The P use efficiency (PUE) when fertilizer-P sources were added alone by Mombasa grass was <12% of the added P, and PUE decreased as follows: TSP > RPA > RPM. When P and N-fertilizer were added together, the fertilizer-N use efficiency (NUE) was 62%. The reactive phosphate (RPM and RPA) is an efficient P sources for Mombasa grass, but requiring higher rate of application compared to TSP source.

SUMMARYAmong the production factors, adequate fertilization is an important tool to raise the productivity of pastoral systems and consequently increase the share of Brazil in the supply chain of primary agricultural products at the global level. The objective of this study was to evaluate the interaction of nitrogen and sulfur fertilization in Brachiaria decumbens Stapf. The experiment in pots with Dystrophic Oxisol was evaluated in a completely randomized design with four replications in a 5 x 3 factorial arrangement, involving five N doses (0, 100, 200, 400, and 800 mg dm -3 ) in the form of ammonium nitrate and three S doses (0, 20 and 80 mg dm -3 ) in the form of calcium sulfate, with a total of 15 treatments. In the treatments with low S dose, calcium was provided as calcium chloride, to ensure a homogeneous Ca supply in all treatments. The results showed that the tiller production and dry weight of green leaves and of stems + sheaths and total dry weight were favored by the combination of N and S fertilizer, while the proportion of dry leaves was reduced. Nitrogen fertilization raised the N contents in green leaves and stems + sheaths and reduced K contents in fresh and dry leaves. The response to S rates in the N content of green leaves was quadratic.Index terms: fertilization, Brachiaria decumbens, plant nutrition, forage plants.(1) Received for publication on July 3, 2012 and approved on May 14, 2013.(2) Professor, Univ Estadual Paulista "Júlio de Mesquita Filho", UNESP/Campus de Dracena. Rodovia SP 294, km 651. CEP 17900-000 Dracena (SP

RESUMO:A compreensão sobre a influência da aplicação de vinhaça na decomposição do palhiço e seus efeitos nos atributos químicos do solo e na cultura da cana-de-açúcar é essencial para o bom gerenciamento desse sistema produtivo. Objetivou-se com este estudo avaliar o tempo de decomposição e a ciclagem de nutrientes do palhiço de cana soca (3º ciclo), e seus efeitos sobre os atributos químicos do solo e nas características tecnológicas da cultura, em função de doses de vinhaça. O trabalho foi desenvolvido na região noroeste do estado de São Paulo, sob Argissolo Vermelho Eutrófico, utilizando-se a variedade RB855453. O delineamento experimental utilizado foi o de blocos casualizados com parcelas subdivididas no tempo. Os tratamentos foram constituídos pela aplicação de 4 doses de vinhaça (0, 50, 100 e 200 m 3 ha -1 ). Houve redução de 20,9% da quantidade de palhiço remanescente durante um ano de avaliação. As doses de vinhaça incrementam a produtividade da cana soca, sem interferir na qualidade da matéria prima. O sistema de cana-crua, em que o palhiço fica depositado sobre o solo e a aplicação de vinhaça, modificam a dinâmica da decomposição do palhiço e alteraram a fertilidade do solo, contribuindo positivamente para a produtividade da cultura. PALAVRAS-CHAVE:Saccharum spp. Fertirrigação. Ciclagem de nutrientes.

Adequate pasture management is important to ensure animal production. The objective of this study was to evaluate the effect on shoot dry weight yield (SDWY) and mineral composition in degraded pasture (Urochloa decumbens) recovery in a Typic Oxisol with introduction of Stylosanthes and phosphorus (P) fertilization. The experiment was set up as completely randomized block design in a split-plot arrangement with four replicates. The plots were seven management system: T1 - Control Urochloa decumbens without Stylosanthes; T2 - U. decumbens + Stylosanthes with no-till; T3 - U. decumbens with partial desiccation + Stylosanthes; T4 - U. decumbens with total desiccation + Stylosanthes; T5 - U. decumbens + Stylosanthes with soil scarification; T6 - U. decumbens + Stylosanthes with plowing;  T7 - U. decumbens + Stylosanthes with plowing + harrowing and the subplots was the P fertilization (presence and absence). P fertilization (60 kg ha-1 of P2O5) increased the P concentration and SDWY of U. decumbens, while the introduction of Stylosanthes in the different management systems used did not change the forage yield.