Conservation agriculture Tanzania_casestudy.pdf - Sokoine ...

Planting calendarsFull cultivation, including placing seed and fertilizer, uses 32 person hours perhectare. The ripper, which opens a planting furrow, enables a whole farm to beplanted before onset of rains and provides good seed germination. Time andlabour savings from ripping are used to increase the area under cultivation,typically by 20–50%. Therefore, household workload for conservation agricultureis not reduced (fig. 4). Labour saved by spreading out the demand for it enablesconservation agriculture households to plant and weed without having to spendscarce cash to hire labour.Weeding calendarsConservation agriculture technology shortens the weeding calendar and increasestimely operations. In conventional cultivation, farmers use hand hoes to weed.Weeding starts about two weeks after planting. Since it takes 20–30 person days toweed one hectare, weeds germinate profusely in the other fields. Subsequently, cropyields drop, drudgery for women and children increases, and school attendancedrops. Under conservation agriculture, weeding is done by ox cultivator. Weedinghas to be done twice, leaving a two- to three-week interval. A cultivator with a pairof oxen or donkeys can weed one hectare in 7.5–8 hours. Farmers said that theamount of weeds in fields planted with mucuna in the previous year was greatlyreduced, making weeding easier.Changes in soil fertility and erosionThe soil fertility in the study area is typically low and the soil needs fertilizer.However, fertilizer costs have restricted their use. Only 60% of farmers inWanging’ombe use commercial fertilizers, either at or below the recommendedrates of 0 phosphorus and 20 kg nitrogen per hectare. Farmers noted that theripper opened small furrows without disturbing the soil and left crop residueand cover crops as mulch, which, after decomposing, improves soil fertility.6050403020100Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMonthBefore CA With CA RainfallFigure 4. Agricultural workload and rainfall in Wanging’ombe Division(Wanging’ombe fi eld station rainfall data).132 Mkomwa et al.