Masters Thesis
Soil nitrate test of Soil Doc protocol has potential to identify optimum N fertilizer requirements for optimizing economic return, while reducing environmental impact. The purpose of this study was to develop N fertilizer requirements for maize production based on the soil nitrate test for the tropical soils in Morogoro District, Tanzania using soil Doc Protocol. Composite soil samples were collected pre-planting (PPNT) and pre-topdressing (PTNT) of N fertilizers to determine soil NO3-N. The PPNT soils samples were also used for determining soil physical and chemical properties. The experiment was conducted in the two villages, the treatments consisted of two soil NO3- level (medium and high) , three nitrogen fertilizer rate: 80 kg N ha-1, 40 kg N ha-1, and control (0 kg N ha-1 arranged in a randomized complete block design (RCBD) with factorial treatment structure. Initial soil properties were medium salinity pH and extremely low organic carbon and available P for all soils in both villages. The results revealed that maize growth parameters (fresh weight, dry weight, grain yield and total N) increased significantly (p<0.001) with increase in nitrogen fertilizer rate. The 80 kg N ha-1 rate had significantly highest response. Also there was no significant interaction between soil NO3 level and fertilizer rate. The results at two sampling times were statistically not significant different. The soil nitrate levels increased over time from PPNT sampling to PTNT time of sampling but did not affect the response to applied N fertilizer. Therefore it is worth to apply N fertilizer to these soils for optimum maize production. It was recommended that more studies should be conducted in different tropical soils, climates and location to determine how soil NO3-N at different stages of maize growth can guide N fertilization.
BASIS AMACRSP project