Green manuring with sunn hemp and the production of the sugarcane variety RB867515, in the cane-plant cycle

Abstract

Several managerial and agricultural techniques have been proposed for the implantation and management of sugarcane fields, aiming at high productivity in the cane-plant cycle and small decreases in regrowth. Green manuring with sunn hemp is one of these techniques. Thus, the objective of the present study was to evaluate in a small rural property, in the edaphoclimatic environment of Mercês, Zona da Mata Mineira, the accumulation of dry matter and nutrient cycling by sunn hemp and by plants in the fallow area, on the nutritional status, the production of forage and industrializable stems using the RB867515 variety. In September, limestone and gypsum were applied based on the results of soil samples in the 0 to 20 cm and 20 to 40 cm layers. Then the soil was plowed and harrowed. At the beginning of October, shortly after the first rains, the study was installed, consisting of an area with sunn hemp sowing and another fallow area. At the beginning of February of the year following sowing, the accumulation of dry matter and nutrients in the aerial part of sunn hemp and in the plants in the fallow area was evaluated. Subsequently, sunn hemp and vegetation from the fallow area were incorporated into the soil, followed by planting RB867515. In January of the year following planting, the nutritional status of the sugarcane was evaluated in the area previously cultivated with fertilizer and in the fallow area, systematically sampling at seven points in the crop. In July, when the sugarcane was mature, the production of forage and industrializable stems was evaluated, sampling in the same places used for the evaluation of the nutritional status. The results obtained were subjected to analysis of variance and means compared by the t test at 5% probability. Crotalaria juncea cultivation resulted in greater nutrient cycling than the vegetation in the fallow area, especially for nitrogen. No difference was observed in the nutritional status of RB867515, comparing the plants from the area previously cultivated with Sunn hemp and those from the fallow area, both of which were well nourished. Green manuring with Sunn hemp increased forage production and the production of industrializable stems. In the area formerly with crotalaria juncea, the plant's aerial biomass production was 20.30 t of natural matter more than in the fallow area. For the production of industrialable stalks, green manuring increased production by 16.7 t per hectare.