Adoption of balanced use of chemical fertilisers: Farmers' response to scientific evidence and social learning

Consumption of chemical fertilisers (mainly Urea, Phosphates and Potash or NPK) has risen rapidly in Bihar in recent years, faster than in the rest of India, and the farmers of Bihar now use higher quantities of NPK per hectare of net sown area (200 kg/ha) than the national average (135 kg/ha). Despite that, crop yields are still generally lower in Bihar. A more balanced usage of fertilisers and increased use of secondary nutrients and micro-nutrients, such as Zinc, Sulfur, Boron, etc. as required, can help increase crop yields and farmers profits and reduce soil and water contamination and fertilizer subsidy burden.

This research project seeks to test the hypothesis that providing soil test based crop-specific fertilizer use recommendation to farmers will encourage more balanced application of fertilisers using a randomized control trial in three rice growing districts of Bihar viz. Bhojpur, Nawada (South Bihar) and Madhubani (North Bihar). Fertilizer use intensity (kg of NPK applied by per hectare of net sown area) is relatively low in Madhubani and higher in Nawada and Bhojpur. From a total sample of 864 farmers drawn from 48 villages in 16 blocks across these three districts, 576 farmers have been randomly selected to receive treatment. We will collect soil samples from their largest plot of land of each farmer in the treatment group and have them tested in the soil testing labs of Rajendra Agriculture University (RAU), Bihar and deliver soil health cards (printed in Hindi) to farmers before the onset of paddy season. Each soil health card will have information on soil characteristics like its organic carbon content (OC), PH, salinity, concentration of Phosphorus, Potash, Sulfur, Zinc and Manganese and scientific recommendations on the quantity of these nutrients the farmer should apply to his or her paddy crop. A team of locally hired extension workers will explain the soil test results and recommendation to treatment farmers in their language. These extension workers will be trained by experts at RAU.

We will know the current (or pre-treatment) fertilizer use levels of farmers in both treatment and control groups from our baseline survey. The experiment will begin in April and will continue throughout the kharif paddy season in 2014. We will monitor application of fertilisers (and other inputs) of our treatment and control farmers in their three largest plots (including the plot from where soil samples were tested) through the paddy season. Crop-cutting exercise will be used to measure paddy yields at the time of harvest. Comparing fertilizer application, crop yields, and net profits of treatment and control farmers will allow us to measure the causal impact of soil-test based extension effort on these variables. We will also collect data from farmers in the close network of our treatment farmers to estimate the spillover (or network) effects of our treatment.