Compost Addition Effects upon Sweet Sorghum Biomass Productivity and Sugar Content

Abstract

Nitrogen availability generally limits plant growth. In order to reduce consumption of chemical fertilizers in agriculture organic amendments are usually incorporated. Among them compost usage is common. The experimental results presented and discussed below were done in order to find out the effects of compost additions on sweet sorghum biomass productivity and stalk sugar content, employing a partial substitution strategy of inorganic nitrogen by organic nitrogen from compost up to total substitution and at three levels of total nitrogen. We found an increasing positive trend between stalk biomass productivity and compost additions for all nitrogen levels tested. Maximum stalk productivity of 56 and 57 Mg/ha on wet basis were obtained with 100 % compost at 100 and 150 kgN/ha levels respectively. A minimum value of 32 Mg/ha on wet basis was obtained by the first cut sample at 50 kgN/ha employing only inorganic fertilization. The ratoon data was higher than those of the first cut for all cases. A significant linear model was adjusted to the first cut data between pressed juice total sugars and the ratio between reducing sugars and sucrose, which indicated a negative correlation among the variables. The data distribution suggested that compost fertilization induced a low ratio and higher sugar content in the stalk.