ABSTRACT
Family farming is important for the production of food for human consumption, but it lacks resources to invest in the soil fertility of its crops. The objective of this study was to analyze whether the use of green manures increases soil fertility in terms of the nutrients N, P and K with low environmental risk for family agricultural production. An experiment was set up in the State of Mato Grosso (Brazil), in randomized complete block design, with a 6 x 3 factorial scheme, four replications, corresponding to 6 types of plants and 3 doses of phosphorus. Leguminous green manure plants were: velvet bean, Crotalaria juncea, Crotalaria ochroleuca and dwarf pigeon pea, in addition to plots with pearl millet and weedy fallow control. Rock phosphate (i.e., reactive natural phosphate) was applied as a source of phosphorus at 0, 50 and 100 kg P2O5 ha-1. The species used as green manure were cut in full bloom and the levels of N, P, K and C in plants and soil were determined. Leguminous green manure plants, after mineralization, increased the stocks of N, P and K in the soil. Crotalaria juncea was the one that reached the highest N accumulation in its constitution, being recommended in the intercropping with species with C/N ratio > 30 to minimize risks of contamination with nitrate in the soil. This work concluded that the managements with green manure plants, especially Crotalaria ochroleuca, are recommended and environmentally safe technical alternatives for family farming.
Keywords:
Mineralization; Soil fertility; Legumes
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CJ: Crotalaria juncea; CO: Crotalaria ochroleuca; PP: pigeon pea; MI: millet, VB: velvet bean and SV: spontaneous vegetation. SE: standard error of the mean. Data transformed to Log (x) for statistical analyses. Different uppercase letters indicate significant difference between green manure plants (ANOVA and Tukey test - p<0.05). Absence of letters indicates that there was no significant difference (ANOVA - p>0.05).
CJ: Crotalaria juncea; CO: Crotalaria ochroleuca; PP: pigeon pea; MI: millet, VB: velvet bean and SV: spontaneous vegetation. SE: standard error of the mean. Data transformed to Log (x) for statistical analyses. Different uppercase letters indicate significant difference between green manure plants (ANOVA and Tukey test - p<0.05). Absence of letters indicates that there was no significant difference (ANOVA - p>0.05).
CJ: Crotalaria juncea; CO: Crotalaria ochroleuca; PP: pigeon pea; MI: millet, VB: velvet bean and SV: spontaneous vegetation. SE: standard error of the mean. Data were transformed to Log (x) for statistical analysis. Different uppercase letters indicate significant difference between green manure species; different lowercase letters indicate significant difference between P doses for each green manure plant (ANOVA and Tukey test - p<0.05). Absence of letters indicates that there was no significant difference (ANOVA - p>0.05).
CJ: Crotalaria juncea; CO: Crotalaria ochroleuca; PP: pigeon pea; MI: millet, VB: velvet bean and SV: spontaneous vegetation. SE: standard error of the mean. Data were transformed to Log (x) for statistical analysis. Different uppercase letters indicate significant difference between green manure species; different lowercase letters indicate significant difference between P doses for each green manure plant (ANOVA and Tukey test - p<0.05). Absence of letters indicates that there was no significant difference (ANOVA - p>0.05).
CJ: Crotalaria juncea; CO: Crotalaria ochroleuca; PP: pigeon pea; MI: millet, VB: velvet bean and SV: spontaneous vegetation. SE: standard error of the mean. Data were transformed to Square Root (x + 1) for statistical analysis. Dashed lines represent the limits between mineralization/immobilization of plants and soil. Different uppercase letters indicate significant difference between green manure species. Absence of letters indicates that there was no significant difference (ANOVA - p>0.05).