Published 2009-12-01
Abstract
Sunn hemp (Crotalaria juncea L.) is a tropical leguminous cover crop grown June through August in Florida. In organic production systems, effi cient cycling of nutrients including K is critical to minimizing the high costs of compliant fertilizers. To determine the capacity of sunn hemp K uptake and the influence of K on aboveground biomass production, three rates of K (45, 90, and 180 kg·ha–1) as potassium magnesium sulfate (22% K2O) were compared to a control of 0 K. Treatments were randomized and replicated three times. Sunn hemp was seeded to 28 kg·ha–1 on 15 May 2008 at Plant Science Research and Education Unit in Citra, FL. Percent K in sunn hemp stem tip tissue (top 15 cm) increased linearly with rate (y = 0.004x + 1.98; r2 = 0.12) and declined linearly with time (y = –0.44x + 3.57; r2 = 0.73). Total K in aboveground dry plant tissue increased with increasing K rate (y = 0.005x + 1.92; r2 = 0.58) at 6 WAP. Potassium accumulation in aboveground tissues at 6 WAP was 68 kg·ha–1, indicating the potential for some K provision to subsequent crops in short rotations.