Sustainable management of crop growth necessitates the application of chemical fertilisers and amendments along with addition of required quantity of organic matter. Soil test based fertiliser application offers a viable solution towards reduction in cost of cultivation and the judicious use of fertilisers and inputs. It also increases the efficiency of individual nutrients by preventing possible nutrient imbalances arising out of blanket fertiliser application. More over the imbalanced application of fertilisers unnecessarily invites the attack of pests and also causes environmental damage through leaching of chemicals to water bodies thereby reducing its carrying capacity. Soil testing involves collection of field samples and analysis in the laboratory for the essential nutrients.

Soil Sampling

The entire area has to be grouped based on the soil colour, structure, texture and slope of the area. Areas having similar characteristics are grouped and representative samples are taken. 'V' shaped cuts of 30cm depth are taken at a distance of 1.2m from the basin and the samples are taken from the sides of 'V' by gently scraping the soil. The samples are then pooled and quartered to get a final composite sample o approximately 500 gram. This is later dried in shade and labeled properly for analysis in the laboratory.

Application of fertilisers

In order to ensure better use efficiency of nutrients, soil reaction has to be corrected before the application of fertilisers. In the case of acid soils the pH has to be altered to the range of 6.0-6.5 by adding lime or dolomite@1kg per palm approximately two weeks before the application of fertilisers. Choice of fertiliser input for each nutrients depend on the availability of the material as well as the soil condition prevailing in the locality.

Based on the soil test values fertilisers are to be applied in split doses. Under Kerala conditions receiving rainfall from two monsoons, one third of the total fertilser is to be applied at the time of early south west monsoon showers during May-June and 2/3rd is to be applied during September-October. If irrigation facilities are available fertilisers can be applied in four split doses.

In the case of phosphorus fertiliser, rock phosphate can be applied in acidic soils whereas single super phosphate can be applied in normal neutral soils.