I think Indian farmers are overdosing soils with nitrogen. There is indiscriminate use of nitrogenous fertilizers like urea to enhance the crop yield leading to deterioration of the soil quality. The unchecked use of nitrogenous fertilizers in state of Punjab is killing farmlands. The use of nitrogen in farming should not exceed four times the amount of potassium. However, in Punjab the average use of nitrogen is 57 times the amount of potassium.
I think not only in India but in all part of south Asia farmers are using more nitrogenous fertilizer specifically Urea as suggested by Dr. Arvind. From past 3-4 decades farmers are applying more amount of nitrogen in the soil in aim of improving the productivity.
Let me give the example of Nepal. Soil of Nepal was rich in potassium and phosphatic minerals in past. So past recommendation dose was made on basis on the nutrient supplying capacity of soil at that time. However, at present ,amount of potassium is medium and phosphorus is very low in soil due to dilution effect. Farmers continually supplied urea and low amount of P and K which means lots and lots of extraction of native soil P and K and content of those nutrient in soil went on decreasing.This is one of the primary reason for stagnant yield for rice-wheat system not only in Nepal but as a whole in South Asia.
"Seeing is believing", average farmer see the effect of urea promptly. However effect of other nutrient can't be visualize as quickly as nitrogen. As most of the farmers are unaware of nutrient ratio required they apply increasing dose of nitrogenous fertilizer to enhance yield which exacerbate the problem creating more gap between Nitrogen and other nutrient. I believe Site specific Nutrient Management (SSNM) will be the best way to cope with this discrimination. Until nutrient required on basis of present nutrient supplying capacity is not made and farmers are not made more ware this situation might pursue even in the future too.
Are you talking about the small and marginal farmers...? If , we are addressing those farmers , i do not think , they using such overdoses of N and P fertilizers ? Such issue , infact , emerged from bigger farmers using such high doses of N and P fertilizer , because of their resourcessfulness. Atleast , this is the factual scenario in southeast Asia.
Thank you for your inputs, Drs. Adhikari and Srivastava.
Dr. Srivastava, I am talking about 'an average Indian farmer' in the question and it had a broader sense..
I asked this question because overdosing issues of specially nitrogen have surfaced in recent past. P fertilizers are relatively expensive therefore, as you also mentioned, their overuse is still limited to resourceful farmers.
More than over-use of fertilizers , i feel , the very basis of such over-use of fertilizers , why does it happen ..?. Is it the non-availability of soil test- based fertilizer recommendation , unable to interpret the situation in right perspective in the context of changing yield performance ..?
Looking to the aforesaid opinion of different scientists. Though our farmers are using excess nitrogen as compared to other major nutrient s like P and K. Still our soils showing low in available nitrogen because of tropical nature of climate. Most of the applied N lossed through voltalization in paddy soils and in dry climate due to cracking nature of soil. However, NPK should be applied in balanced ratio. Most our studies on split appication of N and K showed good response in sugarcane, cotton and maize.
Therefore, there is need to revise our old recommendations.
My experiences are quiet different. I have been associated with Soil Testing Services since last 16 years under Department of Agriculture, Govt. of West Bengal. What I am observing that a sizeable portion of soil samples tested in the laboratory are with high P content. I have interacted with many farmers to find out the causes of such result. And in most cases I have noticed that they use more Phosphate than Nitrogen. In many cases they overlook the ratio of N:P:K in the fertilizer and ignore to adjust the required amount of nutrient to be applied in the field. In rice, which is the main crop in West Bengal, most of the farmers prefer to use DAP as basal application and in many cases they also top dressed this fertilizer and doses of P become higher. As Dr. Raj Adhikari mentioned " farmer see the effect of urea promptly" , they also see the harmfull effect of overdosing with N promptly and for this reason many farmers, now a days are very cautious on overdosing of N fertilizer.
How shall we establish , first , those farmers using over-doses of N and P fertilizers , and second , how shall we monitor such over-doses of fertilizers on a country wide scale..?
Now - a-days most of the farmer use DAP and MOP use for cultivation of rice without top dressing of N as urea in the entire rice crop in eastern plateau region. There is imbalance of NPK. It has been observed that, continuous application of DAP has caused build up of P in the soil.
In my opinion. Yes. Especially for rice crop. It was published in one news article as well which indicated about increased nitrate concentration in ground water due to overuse of fertilizers.