CASSAVA LEAF LITTER ESTIMATION IN ON-FARM TRIALS

Abstract

Cassava (Manihot esculenta) returns organic matter and nutrients to the soil through leaf litter and these amounts need to be quantified to help understand and design sustainable cropping systems. Our objectives were to estimate dry matter and nutrient contents in cassava leaf litter and to derive relationships between litter fall and easily measurable cassava yield components. Litter traps (1 m²) were placed in farmers' fields for monthly monitoring during a three year period. Maximum monthly leaf litter production ranged from 0.5 to 1.0 t ha⁻¹, and occurred at the end of the first rainy season and at the onset of the next rainy season. In the first year, the mean dry matter of leaves collected during 12 months of growth was 3.4 t ha⁻¹ for the unamended treatment, and 4.1 t ha⁻¹ when N-P-K fertilizer was applied. The totals were 2.4 and 3.0 t ha⁻¹ in 2000–2001 and 1.6 and 2.5 t ha⁻¹ in 2001–2002, respectively. Annual differences were apparently related to rainfall. The relationship with fresh root yield was best described using one slope and yearly intercepts giving an r² of 0.63. This relationship can be exploited for estimating litter dry matter in agronomic experiments when rough estimates are sufficient, keeping in mind that the relationship may not be the same for cultivars of differing architecture. Otherwise, the use of litter traps gives the best estimate of annual litter production.