As defined by FAO, Conservation agriculture aims to achieve sustainable and profitable agriculture and subsequently aims at improved livelihoods of farmers through the application of the three CA principles: minimal soil disturbance, permanent soil cover and crop rotations. Permanent soil cover can only be achieved if residue is left on the field after harvest.
Leaving crop residue on the fields has many known beneficial effects. For one, the residues are used as a nutrition source for soil organisms which slowly break it down into smaller and finer particles which end up constituting soil organic matter. This in turn is broken down providing nutrition for crops and reducing fertilizer requirements.
Maintaining residue on the field, both above and underground is a well known soil conservation or erosion control measure. Residue protects the soil from wind erosion, it slows down and prevents water from running off and acts as a wick allowing rain water to infiltrate deep into the soil, recharging it with water. Furthermore the residue acts as a continuum gap between water in the soil and water in the atmosphere, which basically means that evaporation of soil water, in a soil covered with residue, is diminished. Soil conservation and water conservation are the two sides of the same coin. Water harvesting can only be done if the soil is in a healthy state, physical, chemical and biological.
Satellite imagery is becoming common practice in precision farming. Satellite imagery is processed as Normalized Difference Vegetation Index (NDVI) which is an index that shows the health of the crop across fields. It is used to identify areas of poor crop performance, weed infestation, pest and disease damage. Crop Nutrition Laboratory Services are now offering a full precision farming package that allows the farmer to get satellite imagery of his farm on a weekly basis (http://goo.gl/2oGIHm).
This imagery is directly sent to their phone and they can view the NDVI maps on their devices using our mobile app called seeCrop. The maps allow the farmers to do intelligent crop scouting directly to areas that have problems so that these can be identified real time and their problems assessed whether through visual observations or deeper investigation through further soil sampling or leaf sampling. It is worth remembering that the quickest way to increase yields is to correct and improve poor performing areas.
Where is the link between satellite imagery and residues you may ask? One of our most recent satellite images has clearly identified all the benefits of the residues on a farm in Nakuru. The farm practices conservation agriculture using no-till planters to plant in between crop residues. This farm had a fire late last year that spread across a number of fields and which burnt all the residues. The same fields and the surrounding fields have been planted in February with Sunn Hemp (Crotalaria juncea L.) as a cover crop as it increases soil organic matter, it fixes nitrogen and it does not harbour nematodes.
One month after planting the satellite image clearly shows where the crop is performing well and where it isn’t. Using the words of the farmer “The poorer crop growth directly mirrors where the fire was”. The NDVI map clearly shows that where the residue was burnt by the fire, crop establishment has been poorer (lower NDVI value). Crop establishment has been very good (high NDVI) in those fields where the residue was not affected by the fire. The exposed soil was not able to store that key moisture that would have guaranteed the emergence of the seeds, resulting in a much lower emergence rate and, eventually, this will turn into an economical loss.
This example is a great manifesto to the advantages of conservation agriculture and no-till farming.