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da Ribeiro L.S.,Engenheiro Agronomo Banco do Nordeste BNB | Dos Santos A.R.,Federal University of Recôncavo da Bahia | da Souza L.F.S.,Pesquisador da Embrapa Mandioca e Fruticultura Tropical | Souza J.S.,Bolsista Fapesb
Revista Brasileira de Ciencia do Solo | Year: 2010

This greenhouse study evaluated the effect of potassium-rich silicate rocks (alkaline ultramaphic, pyroclastic breccia and phlogopite) on the release of K and other chemical nutrients of the soil. A Yellow Latossol with 0.03 cmolc dm-3 K soil was used in the study. The rocks were tested at doses of 75, 150, 225 and 300 kg ha-1 K2O with and without lime, applied to increase the soil base saturation (V-value) to 70 %. The rock and lime materials were mixed with the soil in the pots, watered to 80 % of the soil field capacity and incubated for 45 days. An additional pot containing soil and KCl, the reference K source, was also incubated. After incubation, soybean was sown to evaluate the effect of rock dissolution in a cultivation environment. Plants were harvested 50 days after sowing. Potassium was released in greatest amounts to the soil from ultramafic alkaline and pyroclastic breccia. Liming did not influence the rock dissolution process and K release.

Ritzinger C.H.S.P.,Pesquisador da Embrapa Mandioca e Fruticultura Tropical | Fancelli M.,Embrapa Mandioca e Fruticultura Tropical | Ritzinger R.,Embrapa Mandioca e Fruticultura Tropical
Revista Brasileira de Fruticultura | Year: 2010

Due to their economic importance being unknown in most crops, apart from other pests, plant-parasitic nematodes have been frequently neglected in the agroecosystems, assuming 'status' only when their population is very high, causing accentuated damages which leads to significant yield losses. Nevertheless, only 10% of the nematode universe is parasites causing damages to plants; 25% are free-living forms including bacterivorous, fungivorous, omnivorous or predators according to their feeding habits. The relationship between the nematode population level and the damage level for each crop is unknown. Therefore, pesticides are considered the best control option for farmers, but the indiscriminate use could lead to the instability of soil communities resulting in environmental risk. For the risk evaluation, originated from chemical substances, impacts on different types of soil management, as well as disturbances suffered by the soil, several toxicity tests with nematodes have been carried out and there is an increased demand in their use in highly developed countries. The analysis of the soil nematode communities in some ecosystems, according to their feeding habits and maturity index proved to be a good indicator to the damages caused by pollutants or ecological disturbances. In this review, data that demonstrate that these organisms can be used in a satisfactory way in studies of sustainability of ecosystems, due to their abundance, diversity and responses to the toxicity and environmental disturbances, are presented.

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