Soil nitrate and water dynamics in sesbania fallows, weed fallows and maize.

We hypothesized that the integration of trees into agricultural land-use systems can reduce NO3 leaching and increase subsoil N utilization. A field study was conducted on a Kandiudalfic Eutrudox (Ochinga site) and a Kandic Paleustalf (Muange site) in the subhumid highlands of Kenya to measure changes in soil NO3 and water to 200-cm depth for one rainy season in four land-use systems (LUS): (i) planted tree fallow using Sesbania sesban (L.) Merr., (ii) unfertilized maize (Zea mays L.), (iii) weed fallow, and (iv) bare fallow. Subsoil (50-200 cm) NO3-N at the start of the season ranged from 58 to 87 kg ha-1 for the four LUS and two sites. In maize, subsoil NO3-N differed by