CSS Graduate Student, Lydiah Gatere
Lydiah, under the auspices of her advisors Johannes Lehmann, Peter Hobbs and Stephen DeGloria, is working on yield advantage of conservation farming across a wide environmental gradient in Zambia. The project involves an approach for conserving biodiversity in Zambia's Game Management Areas (GMA), which serve as buffer zones to national parks. Farmers in the GMA have limited land area to accommodate the growing human population which relies largely on subsistence farming. Crop failure or inadequate food production creates increased human pressures to rely on destructive use of wildlife and other natural resources to compensate for food deficit. Furthermore, the traditional chitemene system of shifting cultivation contributes to accelerated rates of soil erosion due to shorter fallow periods and longer cropping cycles caused by increased population pressures. These problems have led to the introduction of improved technologies and natural resource management options to intensify agricultural production in the GMA and to prevent this wildlife agriculture.
Conservation farming (CF) as applied in Zambia involves a package of several key practices: dry-season land preparation using minimum tillage systems; no burning but crop residue retention from prior harvest; planting and input application in fixed planting stations; and crop rotations including nitrogen-fixing plants. For hand hoe farmers, CF revolves around dry-season preparation of a precise grid of permanent basins (15,850 per hectare). Unlike the conventional hand-hoe and plowing technologies they replace, CF moves only about 15 percent of the soil where crops will be planted. Thus breaking the existing hardpan, improve water infiltration and plant root development, harvest water in years of sporadic rainfall, greater efficiency and precision in use and application of inputs. This results in gradual build-up of soil organic matter. By reallocating land preparation to the dry season in advance of the rains, CF relieves peak-season labor bottlenecks, thus enabling early planting and early weeding.
Photo courtesy of Lydiah Gatere
A conservation farming plot / a traditional plot in the background.
The area was subdivided on physiographic basis into three landscape agroecological zones where variability in mean annual precipitation, temperature, soil texture and landscape position are major determinants of soil, water and nutrient availability. The altitude ranges from 500m – 1400m above sea level while mean annual rainfall across the gradient is 500- 1500 mm per annum with unimodal distribution pattern from November to April. The study establishes the effects of mean annual precipitation, percentage clay content and landscape position on crop yields under a wide environmental gradient through CF. It also determines factors influencing yield improvement by additions of organic amendments along the gradient. It is hypothesized that CF increases crop yields the most under extreme adverse environmental conditions of low soil moisture and low N and P availability. A threshold of mean annual precipitation can be established below which conservation farming does not guarantee sufficient crop yields of 2 Mg/ha. The results indicate that grain yield did not significantly increase with farmer managed CF over conventional farming. No difference was detected regarding the random and pre-allocated plots, confirming the validity of comparisons between treatments. It can be concluded that CF as practiced by farmers is not achieving a sufficient yield increase. Introducing improved practices, in particular mineral fertilizers, crop yields increased significantly. The location and agroecological zone significantly affected crop yield, with greater yields at higher elevations, which are the wetter regions. This is confirmed by a slightly positive relationship between yields and rainfall. Very interesting is the proportionally greater increase in crop yields through on grain production.
In a different region of Zambia where farmers have practiced CF for over 10 years, a chronosequence study was done. The effect of time on soil fertility was studied using a false-time series approach. Fields with different lengths of continuous practice of conservation farming were identified on the same soil type and under the same climate. The research would facilitate answering questions like when can a farmer be assured of increased nutrient accumulation so as to reduce the rate of mis-adoption. We hope to develop recommendations for which CF combinations works effectively.
The project is funded by Sustainable Agriculture and Natural Resource Management Collaborative Research Support Program (SANREM- CRSP) http://www.oired.vt.edu/sanremcrsp/index.php which is sponsored by USAID. I am a recipient of the prestigious 2009 Norman E. Borlaug Leadership Enhancement in Agriculture Program (LEAP) Fellows Program.
I grew up in a rustic green landscape, surrounded by rolling hills in Central Province Kenya. I earned my undergraduate degree in Bachelor of Science Horticulture from Egerton University, Kenya and later Master of Professional Studies in International Agriculture and Rural Development from Cornell University, NY.
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