Biomass production and nutrient cycling in leucaena-based alley cropping systems

Abstract:

Much like a natural forest recycles its own nutrients through leaf litter, alley cropping with nitrogen-fixing trees can create a self-sustaining fertility loop within agricultural fields. This research quantified biomass production and nutrient cycling in a Leucaena leucocephala-based alley cropping system with maize at Chiang Mai Agricultural University, Thailand, over two cropping seasons (2021-2022). Leucaena hedgerows (4 m spacing) produced 8.7 t ha⁻¹ yr⁻¹ of pruned biomass, recycling 142 kg N, 18.4 kg P, and 98 kg K ha⁻¹ yr⁻¹ to the soil surface. Soil organic carbon in alley plots increased by 0.34 percentage points over two years compared to 0.08 in sole maize. Maize grain yield in the alley system averaged 4.82 t ha⁻¹, 22.3% higher than sole maize (3.94 t ha⁻¹) at the same fertiliser input. The leucaena system replaced approximately 68% of the recommended nitrogen fertiliser through biological fixation and biomass recycling. These findings support leucaena alley cropping as a practical approach to sustainable nutrient management in northern Thai highlands.