Conservation Agriculture

Conservation tillage is regarded as the best practice for crop production in drylands. However, their effect on the green gram (Vigna radiata (L) Wilczek) has not been much documented in ASALs of Kenya. A field study was conducted during the 2018-2019 short rains with the aim of evaluating the effect of tillage methods and mulch application on the growth and yield of two green gram varieties in Katumani and Mwea. A randomized complete block design (RCBD) with a split-slit plot arrangement and three replicates was used. The main plots were tillage methods zero tillage (ZT), furrow-ridge (FR), and conventional tillage (CT). Subplots were mulched plots with plant residue (3 t·ha−1) and plots without mulch applied (0 t·ha−1) and in the sub-subplots were two green gram varieties (N26 and KS20). Data was collected on plant height, number of primary branches, root biomass, shoot biomass, number of pods per plant, number of seeds per pod, 1000 seed weight, grain weight (t·ha1), and harvest ...

Climate resilient cropping systems are required to adapt to the increasing threats of climate change projected for Southern Africa and to better manage current climate variability. Conservation agriculture (CA) has been proposed among technologies that are climate-smart. For a cropping system to be labelled Bclimate-smart^ it has to deliver three benefits: a) adapt to the effects of climate and be of increased resilience; b) mitigate climate effects by sequestering carbon (C) and reducing greenhouse gas emissions (GHG); and c) sustainably increase productivity and income. Research on smallholder farms from Southern Africa was analysed to assess if CA can deliver on the three principles of climate-smart agriculture. Results from Southern Africa showed that CA systems have a positive effect on adaptation and productivity, but its mitigation potential lags far behind expectations. CA systems maintain higher infiltration rates and conserve soil moisture, which helps to overcome seasonal dry-spells. Increased productivity and profitability were recorded although a lag period of 2–5 cropping seasons is common until yield benefits become significant. Immediate economic benefits such as reduced labour requirements in some systems will make CA more attractive in the short term to farmers who cannot afford to wait for several seasons until yield benefits accrue. The available data summarizing the effects of CA on soil organic C (SOC) and reductions in greenhouse gases, are often contradictory and depend a great deal on the agro-ecological environment and the available biomass for surface residue retention. There is an urgent need for more research to better quantify the mitigation effects, as the current data are scanty. Possible co-interventions such as improved intercropping/ relay cropping systems, agroforestry and other tree-based systems may improve delivery of mitigation benefits and need further exploration.

The adoption of conservation agriculture (CA), based on minimal soil movement, permanent soil cover
with crop residues or growing plants and crop rotation has advanced rapidly in the Americas and
Australia over the last three decades. One of the immediate benefits of CA in dryland agriculture is
improved rainfall-use efficiency through increased water infiltration and decreased evaporation from
the soil surface, with associated decreases in runoff and soil erosion. This paper focuses on the effect of
CA techniques on soil moisture relations in two researcher-managed trials in Zambia and Zimbabwe. In
2005/2006 and 2006/2007, we found significantly higher water infiltration on both sites on CA fields
compared to conventionally ploughed fields. At Henderson Research Station, Zimbabwe, on a sandy soil,
a direct seeded CA treatments had a 49% and 45% greater infiltration rate than the conventionally tilled
plots after a simulated rainfall in both seasons. At Monze Farmer Training Centre, Zambia, on a finertextured
soil, the same treatment had 57% and 87% greater infiltration rate than the conventionally tilled
control treatment in both seasons. Treatments that included reduced tillage and surface residue
retention had less water runoff and erosion on runoff plots at Henderson Research Station, Zimbabwe. On
average, soil moisture was higher throughout the season in most CA treatments than in the
conventionally tilled plots. However, the full potential of CA in mitigating drought was not evident as
there was no significant drought period in either season. Results suggest that CA has the potential to
increase the productivity of rainfall water and therefore reduce the risk of crop failure, as was apparent at
the Monze Farmer Training Centre, Zambia, in 2005/2006 when a period of moisture stress at tassling
affected CA treatments less than the conventionally tilled treatment.