Rice-wheat system provides food, income, and employment to over 83 % of the people and contributes to national food security in Nepal. Sustainability of the system is under threat because of increasing cultivation cost and declining soil fertility. On-farm experiments were carried out to determine the effects of tillage and crop establishment methods, crop residue management, and nitrogen levels that affect soil attributes and productivity of the rice-wheat system during 2010- 2011at Bara, Nepal. The treatment consisted of three tillage and crop establishment methods viz. Conventional tillage (CT), Permanent bed planting (PB), and Zero-tillage (ZT); two residue management levels viz. Residue retention and Residue removal; and three nitrogen levels viz. Zero nitrogen, farmer’s dose (80 and 100 kgha -1 N for rice and wheat, respectively), and abundant nitrogen (120 kgha -1 N for both rice and wheat crop). The experiments were laid out in strip-split plot design with three replications. The research results revealed that rice grain yield was significantly higher in the plots receiving N level as applied by farmers that was similar to abundant nitrogen dose. Wheat grain yield was significantly higher with zero tillage compared to permanent bed planting and conventional tillage. Significantly higher wheat grain yield was also obtained due to abundant nitrogen dose than zero dose nitrogen which was similar to farmers’ dose of N as well. There was no significant difference in grain yield of rice and wheat due to residue retention, although, it improved soil moisture. In wheat crop, zero-till planting and increased nitrogen application conserved soil moisture, enhanced soil electrical conductivity and lowered soil temperature. It can be concluded that rice and wheat can be grown successfully with zero tillage and farmer’s nitrogen dose without any yield penalty. Agronomy Journal of Nepal (Agron JN) Vol. 3. 2013, Page 64-72 DOI: http://dx.doi.org/10.3126/ajn.v3i0.9007

Experimentation by farmers with conservation agriculture (CA) is increasing in southern Africa, but local longer term data on these new production systems are scarce. This study focuses on CA research at two contrasting on-farm sites and one on-station long-term trial in Zimbabwe. The on-farm trials were conducted at Chikato village on a sandy soil at Zimuto Communal Area with low rainfall and at Hereford farm near Bindura on a clay-rich soil in a high rainfall area. The on-station trial was at Henderson Research Station near Mazowe where more in-depth soil studies were possible. Results of CA systems from the on-station site show on average 38 and 65% greater water infiltration on ripline-seeded (RS) and direct-seeded CA treatments compared with conventionally ploughed control treatments. Results from on-farm sites show a 123 and 168% greater aggregate stability at Hereford and 11 and 24% lower dispersion ratio at Chikato on the two CA compared with the conventionally ploughed control treatments. Soil carbon increased by 46% in the first 20 cm on the sandy soils at Chikato in RS and by 104% in direct-seeded CA treatments in four cropping seasons from 2004 to 2008, while it stayed at low levels on the conventionally tilled control treatment. Yields on CA plots were higher on the sandy soils in dry seasons, but lower in very wet seasons because of waterlogging. Yields on clay soils were less affected by the rainfall season. Crop productivity from CA systems increased at all sites over time owing to better management although significant differences between CA and conventional treatments on the three sites were apparent only after several cropping seasons. Conservation agriculture offers practical solutions to small-scale farmers threatened by future soil degradation and fertility loss, but its successful use will depend on weed control and adequate application of fertilizers. The results indicate that there is no immediate increase in maize (Zea mays L.) yield when changing from a tilled to a CA system, but there is gradual improvement in some soil quality indicators over time.

Current degradation of the natural resource base calls for innovative approaches to sustainable agriculture in Africa. Conservation agriculture (CA) is a sustainable cropping system based on minimal soil disturbance, soil cover with crop residues and crop rotations. CA leads to soil organic matter accumulation and improves water harvesting, and therefore more stable yields and a reduction of the risk of crop failure. After several years, soil quality improvement results in greater crop productivity. However, smallholder, resource-poor farmers in Africa generally manage mixed crop/livestock systems and depend on crop residues for animal feed in the dry season. Strategies therefore need to be developed to convert the farm from conventional to conservation agriculture. Step-wise incorporation of CA into the farming system and concentration of plant nutrient resources will allow increased productivity of both food and crop residues. Once productivity is increased part of the crop residues can be used as animal feed while still leaving sufficient residues for soil cover and soil quality regeneration. Greater production stability and reduced labour requirements of CA make it possible for farmers to use part of the farm for higher value crops, thus generating additional income. Reduced labour requirements of CA allow farmers to involve in alternative activities. CA systems, however, are knowledge intensive and although the principles have very wide application, the actual techniques and technologies to apply these principles are site and farmer-circumstance specific, necessitating the development of multi-stakeholder “innovation networks” focused on adapting CA systems to local conditions.

SUMMARY Conservation agriculture (CA) systems are based on minimal soil disturbance, crop residue retention and crop rotation. Although the capacity of rotations to break pest and disease cycles is generally recognized, other benefits of crop rotations in CA systems are seldom acknowledged and little understood. We monitored different conventional and CA cropping systems over the period from 2005 to 2009 in a multi-seasonal trial in Monze, southern Zambia. Both monocropped maize and different maize rotations including cotton and the green manure cover crop sunnhemp ( Crotalaria juncea ) were compared under CA conditions, with the aim of elucidating the effects of crop rotations on soil quality, soil moisture relations and maize productivity. Infiltration, a sensitive indicator of soil quality, was significantly lower on conventionally ploughed plots in all cropping seasons compared to CA plots. Higher water infiltration rate led to greater soil moisture content in CA maize treatments seeded after cotton. Earthworm populations, total carbon and aggregate stability were also significantly higher on CA plots. Improvements in soil quality resulted in higher rainfall use efficiency and higher maize grain yield on CA plots especially those in a two- or three-year rotation. In the 2007/08 and 2008/2009 season, highest yields were obtained from direct-seeded maize after sunnhemp, which yielded 74% and 136% more than maize in the conventionally ploughed control treatment with a continuous maize crop. Even in a two-year rotation (maize-cotton), without a legume green manure cover crop, 47% and 38% higher maize yields were recorded compared to maize in the conventionally ploughed control in the two years, respectively. This suggests that there are positive effects from crop rotations even in the absence of disease and pest problems. The overall profitability of each system will, however, depend on markets and prices, which will guide the farmer's decision on which, if any, rotation to choose.

Most models predict that climate change will affect the southern African region both through temperature rises and increased frequency and severity of drought. Conservation agriculture (CA) based on minimal soil disturbance, crop residue retention, and crop rotations offers potential solutions to mitigate the effects of seasonal drought. In Zimbabwe and Zambia, we investigated the effects of different maize-based CA systems on water relations and crop productivity from 2005-2009 and compared results with conventionally plowed plots. In all seasons, we found higher water infiltration on CA plots, and it was three to five times higher on direct-seeded CA plots compared to conventionally plowed control plots in 2009. This led to higher available soil moisture on CA plots. The increase in soil moisture will enable crops to overcome seasonal dry spells, mitigate the effects of drought, reduce the risk of crop failure, and secure livelihoods in the region.

Conservation agriculture (CA) is characterized by surface crop residue retention and minimal soil movement. It is a complex technology that involves not only a change in many of the farmer's cultural practices, but also a change in mind-set to overcome the use of the plow. CA is knowledge-intensive, and success with the system may depend more on what the farmer does than the level of inputs applied. However, smallholder farmers are generally characterized by weak links to information systems outside those of the community, while close community linkages tend to reinforce traditional activities. They commonly manage complex crop-livestock systems, where crop residues play an important role in animal nutrition. This, coupled with communal grazing rights, makes the retention of sufficient surface residues a difficult practice for small farmers, especially in rain-fed systems where residue production levels are low. Smallholders often have weak links to input and output markets, as well as limited access to capital and credit. These factors complicate access to non-traditional inputs, and to crop diversification and the establishment of crop rotations: an important practice to overcome pest and disease carryover in CA. Adequate equipment for direct seeding is a prerequisite for successful CA, but comparatively few resources have been dedicated to the development of direct-seeding equipment for low draught power conditions, given the relatively small profit margins associated with small equipment. All of these factors stress the need for the catalysis and development of innovation systems focusing on the development of CA in smallholder farming communities, and supporting the efforts of innovative farmers within these. Strategies for the successful adoption and management of CA practices need to address the issue of an enhanced knowledge base of individual farmers and the community. (C) 2007 by The Haworth Press, Inc. All rights reserved.