Cover crop and tillage affect sweet sorghum production and soil chemical properties

Abstract

Sweet sorghum [Sorghum bicolor (L.) Moench] is known for high production potential, even on marginal land. Field research was conducted in northeast and southeast Louisiana for 3 yr to determine the changes of sweet sorghum productivity and soil‐chemical properties influenced by applications of tillage and legume cover crop. Crimson clover (Trifolium incarnatum L.), and hairy vetch (Vicia villosa Roth) were planted in the fall and then compared for the following sweet sorghum production and soil‐chemical properties with those receiving 0, 56, and 112 kg ha−1 of synthetic N fertilizer under conventional tillage (CT) or no‐tillage (NT). Sweet sorghum cultivated after either legume cover crop produced equivalent amounts of sweet sorghum biomass and sugar as those of sweet sorghum receiving 56 or 112 kg ha−1 N fertilization. Increasing N fertilization rates from 56 to 112 kg ha−1 did not increase sweet sorghum production. Proportion of sucrose averaged 48% of fermentable carbohydrate in the juice, followed by glucose (23%) and fructose (16%). The proportion of sugars did not differ regardless of tillage or N treatment. Potential N production from hairy vetch ranged from 74–108 kg ha−1, which was greater than that from crimson clover. The benefit of CT was found in greater fresh biomass and higher plant population of sweet sorghum compared to those of NT. Soil organic matter varied in years and cultivation practices. Due to moderate N demand of sweet sorghum, legume cover crops are promising N providers without sweet sorghum production losses.