On-farm experimentation for scaling-out conservation agriculture using an innovation systems approach in the north west province, South Africa.

A project under the Farmer Innovation Programme (FIP) that aimed to adapt Conservation Agriculture (CA) among grain farmers in South Africa was implemented in a commercial farming area of the North West Province. The following on-farm, collaborative-managed trials produced key findings concerning: (i) plant population densities (high versus low) under CA; (ii) conventional crop systems versus CA crop systems; (iii) the testing and screening of cover crops; (iv) green fallow systems for soil restoration; and (v) livestock integration. Key results from these trials were that the yield of maize was significantly higher under high-density no-till (NT) systems compared to the normal NT systems. The yield of maize in local conventional systems was lower than the yield in NT systems tested on three farmer-managed trials. The screening trial assisted in testing and learning the suitability and the different attributes of a range of cover crops in that area. Cover crop mixtures used as a green fallow system with livestock showed that CA can facilitate the successful restoration of degraded soil.

Managing Scarce water resources for socially acceptable solutions, through hydrological and econometric modeling

Covering increasing water demand for competitive uses with limited resources is becoming one of the most challenging water management issues. The effects are more evident in arid areas, where conflicts are more likely to occur. Such an example is Urumqi County, China; Urumqi River is the main water supply source, and in order to balance the upstream agricultural water demand and the downstream urban water demand, the government imposed fallow measures. The region is traditionally a rural area with high production expectations, however, urban water demand is continuously increasing over the last decades, following the population and urbanization trends. Irrigation needs are covered from the river, during the summer period, creating seasonal demand peaks. The fallow measures aim to sustain agriculture and the government defines which farmers will fallow each year. This study uses a questionnaire survey to examine the farmers’ willingness to continue fallow, and the fallow period preference; both examined for the first time so far. The driving factors are used as variables to analyze and describe the preferences through regression models. A non-negligible portion of farmers highly depend on agriculture and want to cultivate. The feasibility of satisfying their needs through better water management is examined through a coupled WEAP (Water Evaluation And Planning) model. Combining econometric and hydrological tools is a novel element. The results are encouraging, with significant insights on the current water management policy, the potential of diversified fallow systems, and the achievement of sustainable and socially acceptable planning.

Reduction of Nitrogen Fertilizer Requirements and Nitrous Oxide Emissions Using Legume Cover Crops in a No-Tillage Sorghum Production System

Nitrous oxide (N2O) emission from denitrification in agricultural soils often increases with nitrogen (N) fertilizer and soil nitrate (NO3−) concentrations. Our hypothesis is that legume cover crops can improve efficiency of N fertilizer and can decrease N2O emissions compared to non–cover crop systems. The objectives of this study were to (a) evaluate the performance of summer leguminous cover crops in terms of N uptake and carbon (C) accumulation following winter wheat and (b) to quantify the effects of summer leguminous cover crops and N fertilizer rates on N2O emissions and grain yield of the subsequent grain sorghum crop. Field experiments were conducted in the context of a wheat-sorghum rotation for two seasons in Kansas. Treatments consisted of double-cropped leguminous cover crops following winter wheat harvest with no fertilizer applied to the following grain sorghum or no cover crop after wheat harvest and N fertilizer rates applied to the grain sorghum. The cover crops were cowpea (Vigna unguiculata L. Walp.), pigeon pea (Cajanus cajan L. Millsp.), and sunn hemp (Crotalaria juncea L.). The three N treatments (were 0, 90, and 180 kg·N·ha−1). Fallow systems with 90 and 180 kg·N·ha−1 produced significantly greater N2O emissions compared with cropping systems that received no N fertilizer. Emissions of N2O were similar for various cover crops and fallow systems with 0 kg·N·ha−1. Among cover crops, pigeon pea and cowpea had greater C accumulation and N uptake than sunn hemp. Grain yield of sorghum following different cover crops was similar and significantly higher than fallow systems with 0 kg·N·ha−1. Although fallow systems with 90 and 180 kg·N·ha−1 produced maximum sorghum grain yields, N2O emissions per unit of grain yield decreased as the amount of N fertilizer was reduced. We conclude that including leguminous cover crops can decrease N fertilizer requirements for a subsequent sorghum crop, potentially reducing N2O emissions per unit grain yield and providing options for adaptation to and mitigation of climate change.

Carbon Stock as Related to Fallow Age in the Sudano-Guinea Savannahs of Ngaoundere, Adamawa, Cameroon

Aim/Objectives: In order to assess the fallow contribution on the carbon cycle and soil organic matter restoration, a study of the carbon dynamics was undertaken in fallow systems of 1, 2, 5 and 20 years old in the Ngaoundere savannahs of Cameroon. Methodology: Carbon stock was estimated in 100 m2 plot for shrubs, in 1 m2 plot for understorey, litter and earthworm casts, and 0.0625m2 plot for fine roots and soil. The experimental design was randomised complete block with three replicates. The age of fallows was the mean treatment whereas the plots were the replicates. Results: The results showed that the phytomass increased with fallow age, except that of shrubs. Soils and earthworm casts were the mean carbon sinks in the four fallows, with more than 55.61% and 26.24% of the total carbon stock respectively in the soil and earthworm casts. The total carbon stock increased with fallow age, from 34.54 in the young fallows to 154.52 tC.ha-1 in the old fallows. In the same way, vegetation and soil carbon increased with fallow age except that of shrub. The results showed that the carbon stock was influenced by floristic composition and spatial distribution of the vegetation, which related to fallow age. Conclusion: These preliminary results will contribute to the understanding of the impact of fallow age on the global carbon cycle and awareness in the conservation of fallows for the environment protection.