In-situ fertilizer industry for small scale farmers: the case of tephrosia vogelii fallow and minjingu phosphate rock in Eastern Tanzania

Tephrosia vogelii Hook. f. is among the best leguminous shrubs in enhancing soil fertility especially in improved fallow situations in eastern and southern Africa. The objective of this study was to assess the influence of Minjingu phosphate rock (MPR) application and prevailing weather on survival, dry matter, N and P accumulations of Tephrosia vogelii fallow, and maize yields in subsequent season. Tephrosia vogelii fallow was grown for 22 months on acidic P deficient ferralsol amended with 0 or 80 kg P ha-1 at fallow establishment. The survival of T. vogelii plants was monitored over 22 months. Fallow nutrient accumulation was assessed by measuring the quantity and quality of litter commencing at 12 months. The quality of leaves was monitored from 6, 12, 18 and 22 months, while the quantity and quality of stems were assessed at 22 months. Foliar quantity was measured at 22 months. Long dry season significantly (p ≤ 0.05) reduced survival by about 50% in the first 6 months and up to 80% at 22 months. Litter dry weight and stem biomass, were significantly increased (p ≤ 0.05) by MPR application. Foliar P concentration was significantly increased by P application up to 12 months only. The total N and P accumulated in the litter and stems during the 22 months were significantly increased (p ≤ 0.05) by MPR application. In the 22 months period, the total N accumulated in the three plant components were 65.7 and 133.5 kg ha-1 for control and MPR treated plots, respectively. The corresponding values for P were 3.4 and 11.3 kg ha-1. These accumulations led to improvement of maize yields in the subsequent season by 147% relative to natural fallow. Improved fallows of T. vogelli can be used as In-situ fertilizer industry for small scale farmers in the tropics.