Maximizing water and nitrogen management in maize systems in Eastern Kenya

Low soil moisture availability imposes a risk that constrains fertilizer use in Kenya?s maize systems, resulting in a moisture-driven trade-off between water and nitrogen use efficiency. An experiment combining soil moisture conservation practices and nitrogen (N) sources was replicated in two locations (the upper and lower midland zones) of Embu County. Moisture conservation treatments included plastic film mulch, crop residue mulch, soil conditioners (hydrogels), and bare ground, while the N sources were slow-release urea, conventional urea and calcium ammonium nitrate (CAN), and unfertilized control. Experiments were used as training sites for farmers to reinforce the on-farm experimentation process. In both sites, plastic film mulch with slow-release urea and plastic film mulch with CAN significantly increased grain yield, dry biomass, and water-use efficiency compared to the other treatments. Maize crop residues increased water use efficiency by 61.0%, biomass yield by 64.3%, and grain yield by 2.7 t/ha compared to the control plots. Hydrogels with slow-release urea and hydrogels with CAN increased water- use efficiency during the long rainy seasons by 69.8% and 171.3%, respectively.