Edemar Moro

Persistência de palhada e liberação de nutrientes do nabo forrageiro no plantio direto

Straw of covering plants kept on soil surface in no-tillage system is an important source of nutrients for subsequent tillage. The objective of this work was to evaluate decomposition and macronutrients release from forage turnip residues. The experiment was set under field conditions during 1998 in Marechal Cândido Rondon, PR, Brazil. Forage turnip plants were desiccated and lodged 30 days after emergence. Straw persistence and nutrient release were evaluated at 0, 13, 35 and 53 days after management. The experimental design was a randomized block with four replications. Until pre-flowering stage, the forage turnip showed a great dry matter yield (2,938 kg ha -1 ) during winter growing and 57.2, 15.3, 85.7, 37.4, 12.5 and 14.0 kg ha -1 of N, P, K, Ca, Mg and S were respectively accumulated. Forage turnip management at pre-flowering stage cause a quick straw degradation and macronutrients release. Potassium and nitrogen were released in the highest amounts and in the shortest time to the subsequent tillage. Quickest liberation of nutrients occurred between 10 to 20 days after plant management.

Teor de nitrogênio inorgânico no solo em função de plantas de cobertura, fontes de nitrogênio e inibidor de nitrificação

The use of cover crops can change the soil NO 3 - : NH 4 + ratio, providing larger amounts of NH 4 + , and enable the development of crops which absorb more or prefer this form of nitrogen (N), like rice. This study aimed at evaluating the effect of the interaction of cover crops and N sources, with and without nitrification inhibitor (dicyandiamide), under no-tillage system (NTS). The experiment was carried out in 2009/2010, in Botucatu, Sao Paulo State, Brazil, in an Oxisol under NTS for six years. The experimental design was randomized blocks, arranged in a split plot, with four replications. The plots consisted of six cover crops species ( Urochloa brizantha , U. decumbens , U. humidicola , U. ruziziensis , Pennisetum americanum and Crotalaria spectabilis ) and the split plots were seven forms of nitrogen fertilization, at 0 and 30 days after the emergence (DAE) of rice [1 - control, without N fertilization; 2 - calcium nitrate (40 + 40 kg ha -1 ); 3 - calcium nitrate (0 + 80 kg ha -1 ); 4 - ammonium sulfate (40 + 40 kgha -1 ); 5 - ammonium sulfate (0 + 80 kg ha -1 ); 6 - ammonium sulfate + dicyandiamide (40 + 40 kg ha -1 ); and 7 - ammonium sulfate + dicyandiamide (0 + 80 kg ha -1 )]. The use of nitrification inhibitor and the C. spectabilis cover crop resulted in higher levels of ammonium in the soil. The application of the ammonium source without nitrification inhibitor in a total dose at 30 DAE and with inhibitor (split or total dose) resulted in the highest levels of nitrate in the soil.

Nitrate Reductase, Micronutrients and Upland Rice Development as Influenced by Soil pH and Nitrogen Sources

ABSTRACT The average yield of upland rice under no-tillage system (NTS), a sustainable soil management, is lower than in conventional tillage (one plowing and two disking). One of the reasons given for this drop in crop grain yield would be the low-nitrate assimilation capacity of rice seedlings, due to the low activity of the nitrate reductase (NR) enzyme in the early development phase. A greenhouse experiment was conducted to evaluate the effects of the soil acidic and nitrogen source in the micronutrient concentrations, NR activity and grain yield of upland rice growing under NTS. The soil used in the experiment was an Oxisol. The experimental design was completely randomized in a factorial 3 × 4. Treatments consisted of three levels of soil acidity (high, medium, and low) combined with four nitrogen sources (nitrate, ammonium, ammonium + nitrification inhibitor, and control – without N fertilization). The reduction of soil acidity reduced the concentration of zinc and manganese in rice plants. Generally, the activity of the NR enzyme was higher in plants grown in soils with low acidity and fertilized with calcium nitrate. There was a greater response in growth and yield in rice plants grown in soils with high acidity. Under medium acidity, rice plants grown with ammonium sulfate were more productive (no differences were detected with the addition of the nitrification inhibitor).