Is 4:2:1 the ideal ratio for the balanced use of three major plant nutrients - nitrogen (N), phosphorus (P) and potash (K)? The answer is no, not exactly. This norm is a myth held for long without validating it through proper studies. Nobody clearly knows how, when and on what basis this became the accepted standard for balanced fertiliser use.
This misconception has now been debunked. It has been realised that there cannot be a single norm of an ideal nutrient mix valid for the whole country. It varies from crop to crop and area to area, depending on the nutrient status of the soil and numerous other factors. The benchmark of 4:2:1 has been found to apply only to a few situations where the crop productivity responds well to the nutrient application in roughly that proportion, such as in the wheat-rice crop rotation in Punjab and Haryana. Elsewhere, this standard is wide off the mark. Yet, most government publications, including the annual economic surveys, have been using 4:2:1 as the yardstick for assessing imbalance in fertiliser application.
Significantly, the country's apex farm research body, the Indian Council of Agricultural Research (ICAR), has now acknowledged the mistake of treating 4:2:1 as the standard for nutrient application. "The existing fertiliser use norm of 4:2:1 cannot be generalised for the country," the ICAR has said in its Annual Report for 2014-15. A more appropriate all-India average normative nutrient mix would be 2.5:1.4:1, it indicates.
However, when judged against the new normative proportion indicated by the ICAR - 5.2:3:1 - several states are found to err woefully in balanced fertiliser application. Notable among them are Punjab, West Bengal, Haryana, Gujarat, Bihar, Rajasthan and Assam. The report also points out that in Andra Pradesh and Tamil Nadu, all the three plant nutrients are being used in excess of the actual need while in many other states the fertiliser application is dismally inadequate.
"The huge deficit in the use of fertiliser nutrients and the imbalance in relative use of the NPK nutrients need immediate attention of the policy makers", the ICAR asserts.
The data concerning the desired mix of plant nutrients and the actual ratio of their use in different states between 2009 and 2011 shows that the imbalance is far more worrisome than is generally believed. In a state like Rajasthan, for instance, the actual NPK use ratio is as skewed as 25:11:1 whereas ideally it should be 10:5:1 under the prevailing agro-conditions there. Similarly, in Uttarakhand, the actual NPK ratio is 10:2:1 whereas it should ideally be 3:1.5:1. Punjab and Haryana are not too far behind Rajasthan in injudicious use of major plant nutrients. The NPK ratio is 21:6:1 in Punjab and 19:6:1 in Haryana, against the desired proportion of around 4:1.6:1 in both these states.
The numbers given in the ICAR document are a clear indication that most farmers either take arbitrary decisions about the fertiliser use or are misguided on this issue. The application of nitrogen (urea) is generally much higher than is necessary in most cases. The government's ill-advised fertiliser pricing policy, marked by wide disparity in the prices of urea vis-à-vis phosphatic and potassic fertilisers, seems one of the key reasons for this. The lack of soil test-based counsel to the farmers about the use of nutrients is the other significant factor responsible for injudicious fertiliser application.
Thankfully, the government is now trying to address this menace by issuing soil health cards to farmers and expanding the network of soil testing laboratories. But, sadly, there is no move yet to rectify the disparity in the prices of different fertilisers. While phosphatic and potassic fertilisers have been decontrolled and brought under the nutrient-based subsidy scheme, the same has, for inexplicable reasons, not been done in the case of urea. This anomaly needs to be addressed urgently to curb excessive use of urea and bring about a degree of balance in nutrient use, which is vital to enhance crop productivity and maintain soil fertility.
surinder.sud@gmail.com
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