Improve water use through conservation
By Suzette Smalberger: Manager: Agronomy Conservation
Conservation Agriculture (CA) is an approach to managing agro-ecosystems by reducing soil and water erosion, improve soil quality and health, increasing water infiltration to increase profits and food security while preserving and enhancing the resource base and environment.
CA is characterised by three linked principles that will increase water infiltration, reduce soil erosion by wind and water and improve soil biology life. The principals are (1) minimum soil disturbance; (2) permanent organic soil cover; (3) diversification of crop species grown in sequences and/or associations.
In 1973/74, CA was practised on only 2.8 million hectares (ha) worldwide. In 1999 this increased to 45 million ha and in 2003 the area grew to 72 million ha. Over the last eleven years the system grew at a steady rate of 6 million ha per year. In Africa only 1% of our soils is under CA.
How do the three principles help to reduce soil and water erosion?
Minimum soil disturbance
The objective is not to disturb more than 15% of the soil surface. This helps to maintain minerals within the soil, prevent soil compaction from ploughing, maintain soil structure, stop wind and water erosion and prevent water loss from opening up the soil profile.
Permanent organic soil cover
The most commonly identified feature of no-tillage is that as much as possible of the surface residue from the previous crop is left intact on the soil surface. The accepted minimum amount of surface covered by residue after planting is 30%. The cover protects the soil from water and wind erosion by reducing water runoff and evaporation, improve water infiltration and retention resulting in less severe, less prolonged crop water stress and increased availability of plant nutrients. Cover also reduce the impact of rain droplets on the soil surface leading to reduced crusting and surface sealing which leads to the reduction of runoff and erosion. Cover also reduces temperature variations on and in the soil, thus creating better conditions for the development of roots and seedling growth.
Crop rotation is the successive cultivation of different crops in the same field, in contrast to a monoculture system. This helps to improve soil fertility and nutrient availability, especially nitrogen following legume rotation. In conservation agriculture, with crop rotation, different crop roots develop in different soil depths in exploration for nutrients and water. These roots create channels for water movement and next season's roots through the soil profile. Different crop species create a network of channels through the soil profile.
Biodiversity in crop species improve the soil's phytosanitary functions as it prevents the carry-over of crop-specific pests and diseases from one crop to the next. Plants within the same family tend to have similar pests and pathogens. One rotational crop can break or limits the disease cycle.
A diversity of crops in rotation leads to a diverse soil flora and fauna. Different crop roots excrete different organic substances which attract different types of bacteria and fungi. This leads to more diverse microbial populations which improves the soil's ability to resist disease. A decrease in pathogen and pest activity happens through competition. Microbes also play an important role in the transformation of soil substances into plant available nutrients. Best practices prescribe the use of three different crops of which one is a legume.
Conditions for conservation agriculture (CA)
All too often farmers purchase a no-tillage machine after hearing about no-tillage. This led, in many cases, to failure when applying the technology. Only after acquiring good knowledge about all the components of the system should a farmer buy a no-till planter.
Mental change: A mental change away from conventional soil tillage operations towards sustainable production systems such as no-tillage is necessary for success. As long as the head stays conventional, it will be difficult to implement successful no-tillage in practical farming. A farmer first has to change his mind before changing his planter.
There are some critical factors that should be considered before starting no-tillage:
- Improve producer's knowledge about the system, especially weed control and planning for the change-over to CA at least one year in advance.
- Analyse your soil (aim for a balanced nutrient and pH status).
- Avoid soils with poor drainage.
- Level the soil surface if economically feasible.
- Eliminate soil compaction and acidity problems before starting CA.
- Produce the largest possible amount of mulch cover.
- Acquisition of a no-till planter and sprayer.
- Start on only 10% of your farm to gain experience.
- Use crop rotations and cover crops to get the full benefits of the system.
- Training and updating on new developments – form or join a local CA club.
The Omnia agronomist can assist producers in identifying the soil's physical, chemical and biological limitations. Producers have questions related to water management, compaction, soil health, crop rotation and livestock integration – the Omnia agronomist can assist in this regard. Currently, farmers are mostly interested in a practical method to analyse/determine the soil biological status. OmniBio™ is a good indication of soil health.
The agronomic benefits of conservation agriculture (CA) could be summarised in that it leads to the improvement of soil productivity; increase in organic matter; soil-water conservation; improvement of soil structure and therefore an improved root zone.
CA forms the basis of sustainable agriculture where producers will farm in such a way to ensure that they keep on farming in the future. Crop yields will be improved, farmers will be profitable, people will have enough food to eat at a reasonable price and the environment will be conserved. The land farmed is a limited resource. Take care of it today and it will be healthy and productive in the future.