Conservation agriculture Tanzania_casestudy.pdf - Sokoine ...

1 IntroductionOver 80% of the people in Tanzania’s southern highlands depend on farming. Agricultureleads the economy, accounting for over half the gross domestic product.Recent stagnating or declining farm productivity ends in food insecurity and poverty.The southern highlands have four administrative regions, Ruvuma, Mbeya, Iringaand Rukwa, cover 245,000 km 2 or 28% of mainland Tanzania and have about5.82 million people (URT 2001). Altitude ranges from 400 m to 3000 m; annualrainfall varies from 750 mm in the lower altitudes to 2600 mm in the mountainsand along Lake Nyasa. The tropical and temperate climates favour livestock andcrop production.Farmland in the southern highlands is severely degraded, mainly from exploitivefarming. Anecdotal reports suggest compacted soil and reduced productivity inIsmani in Iringa District can be attributed to poor tilling practice, acidified soil inSongea and Njombe highlands from using inorganic fertilizers improperly, and theGreat Ruaha River drying up from deforestation and poor tilling in watersheds, andovergrazing (Taruvinga 1995). Concern is growing that the declining productivityis from unsustainable farming practices. Continuous tillage with the mouldboardox plough in the sandy Njombe soil has created plough pans and low soil organicmatter (Ley et al. 2003). Low and poorly distributed rainfall in both Wanging’ombeand Mshewe wards means crop failures often occur.Conservation agriculture is an approach that aims to overcome land degradationand other productivity problems. It consists of three soil and crop managementprinciples—no soil turning, maintaining permanent vegetative soil cover, androtating both cash and cover crops. Conservation agriculture as initiated in Brazilin the 1980s, and now in some other Latin American countries, has reducedproduction costs, increased yields, increased soil fertility and lowered labour needs.It is a promising alternative for farmers in the southern highlands of Tanzania.Individual components—mulching, subsoiling and ripping—have been practised inthe zone for many generations. Research work encompassing all three conservationagriculture principles was initiated by the Ministry of Agriculture Research Institute(ARI) Uyole in 1999 after a study visit to Brazil by an institute researcher.Farm trials and promotions introduced in Njombe and Mbarali Districts in 1998centred on ridging with animal traction, tied ridging and ripping compared with theconventional mouldboard ploughing. No cover crops were considered. Weeds weremanaged by hand hoeing in ploughed plots, the ridger in ridged plots and contactherbicide in the ripped plots. Cover crops were screened for disease tolerance,establishment, biomass yield and optimal planting time at ARI Uyole.The Tanzania Agricultural Research Project Phase II and Sokoine University ofAgriculture (TARP II SUA) introduced a similar initiative in 2001, which targetedthe same soil and water conserving structures but did away with herbicides anddid not use cover crops. Coverage was expanded to include new villages: Mayaleand Kisilo in Njombe District, Matai and Sandulula in Sumbawanga District andNkundi in Nkansi District. Farmers in each village were trained in groups of 15households.Mbeya District 111