Embu farmers are now well informed in conservation agriculture, thanks to Embu County government and Food and Agricultural Organization. Conservation Agriculture use specialized planting equipment that also allows the placement of fertilizers next to the seeds. Others apply fertilizers by broadcasting them on the soil surface without any problems. The (Cover) crop residues improve the soil moisture content, which makes nutrients in the topsoil more stable for planting.
While officiating the the workshop, FAO County Programme Officer, Mr. Patrick Maina, told the farmers that the crop yields under conservation agriculture are comparable or higher to those obtained under conventional tillage. “If a soil has been tilled for a long time, the changes in the soil resulting from the new conservation agriculture system might be slow at the beginning.” he said.
Mr. Maina said that Conservation Agriculture is a farming system that promotes maintenance of a permanent soil cover, minimum soil disturbance (i.e. no tillage), and diversification of plant species. It enhances biodiversity and natural biological processes above and below the ground surface, which contribute to increased water and nutrient use efficiency and to improved and sustained crop production.
Conservation agriculture uses three main principles. The first one is the minimized mechanical soil disturbance in which Direct seeding or planting is used. Direct seeding involves growing crops without mechanical seedbed preparation and with minimal soil disturbance since the harvest of the previous crop. The term direct seeding is understood in CA systems as synonymous with no-till farming, zero tillage, no-tillage, direct drilling, etc. Planting refers to the precise placing of large seeds (maize and beans for example); whereas seeding usually refers to a continuous flow of seed as in the case of small cereals (wheat and barley for example). The equipment penetrates the soil cover, opens a seeding slot and places the seed into that slot. The size of the seed slot and the associated movement of soil are to be kept at the absolute minimum possible. Ideally the seed slot is completely covered by mulch again after seeding and no loose soil should be visible on the surface.
Land preparation for seeding or planting under no-tillage involves slashing or rolling the weeds, previous crop residues or cover crops; or spraying herbicides for weed control, and seeding directly through the mulch. Crop residues are retained either completely or to a suitable amount to guarantee the complete soil cover, and fertilizer and amendments are either broadcast on the soil surface or applied during seeding.
The next principle is that one of Soil organic cover in which the soil is covered as a fundamental principle of CA. Crop residues are left on the soil surface, but cover crops may be needed if the gap is too long between harvesting one crop and establishing the next. Cover crops improve the stability of the CA system, not only on the improvement of soil properties but also for their capacity to promote an increased biodiversity in the agro-ecosystem. While commercial crops have a market value, cover crops are mainly grown for their effect on soil fertility or as livestock fodder.
The final principle is species diversification whereby crop rotation is practiced. The rotation of crops is not only necessary to offer a diverse diet to the soil micro organisms, but as they root at different soil depths, they are capable of exploring different soil layers for nutrients. Nutrients that have been leached to deeper layers and that are no longer available for the commercial crop, can be “recycled” by the crops in rotation. This way the rotation crops function as biological pumps. Furthermore, a diversity of crops in rotation leads to a diverse soil flora and fauna, as the roots excrete different organic substances that attract different types of bacteria and fungi, which in turn, play an important role in the transformation of these substances into plant available nutrients. Crop rotation also has an important phytosanitary function as it prevents the carry-over of crop-specific pests and diseases from one crop to the next via crop residues.