Government of Nepal approves new site-specific fertilizer recommendations for rice – CIMMYT

Farmer applying urea with a spreader in a paddy field. Photo Uttam Kunwar/ CIMMYT

After four decades, new site-specific fertilizer recommendations for rice have been introduced in Nepal that will help farmers increase crop productivity by 10-30%, compared to their current practices.

The Ministry of Agriculture and Livestock Development (MoALD) endorsed the new fertilizer recommendations for rice cultivation at a consultative workshop in July 2022 held in Kathmandu. Developed by the International Maize and Wheat Improvement Center (CIMMYT), in close collaboration with the Nepal Agricultural Research Council (NARC) National Soil Science Research Center (NSSRC) and International Fertilizer Development Center (IFDC), the new scheme replaces the existing comprehensive approach of recommendations to help increase crop yields and the efficiency of fertilizer use.

The holistic approach assumed that the whole country was a single domain despite heterogeneity in soils, other biophysical conditions, and agronomic management practices, including crop varieties. As a result, fertilizers were underused in low fertility soils or overused in farms with high soil fertility status, so that farmers were unable to obtain the achievable yield.

Unlike generic recommendations, site-specific fertilizer management will help farmers determine crop fertilizer needs based on the soil fertility status of a particular farm, the achievable yield target of the variety selected crop, crop yield response to fertilizers, and agronomic management practices, such as irrigation, cropping systems, etc. In other words, this new regime allows farmers to produce more with less fertilizer through balanced fertilizer application based on available soil properties.

Old is not always gold

Typically, soil fertility status changes every 3-5 years when there is continuous removal of soil nutrients due to intensive cropping system with adoption of improved varieties and hybrids nutrient demanding. Thus, soil fertility management recommendations should be updated periodically but existing recommendations have not been updated since 1976.

Recognizing the limitations, CIMMYT, through the USAID-supported Nepal Seed and Fertilizer Project (NSAF), worked with the NSSRC and IFDC to develop fertilizer recommendations for major cereal and vegetable crops for specific areas of the country.

Under the direction of the NSSRC, a “Fertilizer Recommendation Committee” consisting of a dedicated team of soil scientists within the NSSRC and experts from NSAF was formed to develop site-specific fertilizer recommendations using the Sol-SMART framework for providing balanced fertilizers to farmers. Based on soil fertility status, agroclimate, irrigation regimes and geography, the country has been divided into six soil fertility domains – four in the Terai region (East, Center, West and Far West), one in the inner Terai and one in the hills. In each area, recommendations were based on achievable yield, crop variety and irrigation regime.

This approach was first tested for rice cultivation.

Formulation of new recommendations for rice

Three basic steps were used to develop site-specific fertilizer recommendations, which included: i) selecting the yield target, ii) estimating crop nutrient requirements, and iii) estimating inputs. in native nutrients. To collect this information, NSAF and the committee designed nutrient omission and nutrient ratio field trials to determine yield-limiting nutrients and their optimal ratio, respectively. Data from fertilizer trials conducted by different research institutes and universities, including trials at project sites, were collected and analyzed by the team to see the crop yield response to fertilizers. A modeling approach called Quantitative Assessment of Tropical Soil Fertility (QUEFTS) was also used to estimate the native nutrient supply and attainable yield target of rice for different soil fertility domains. This model was applied as an alternative to extrapolate recommendations in areas where field data was not available, given the significant financial and human resources needed to conduct numerous field trials in different soil types and agro-ecological zones. . The model was validated with field test data before extrapolating the recommendations. The QUEFTS model used soil properties from the first digital soil map of Nepal to identify nutrient condition and deficiencies.

In addition to the optimal agronomic rate, an economic analysis was also conducted to see the economic variability of the recommendations.

The newly developed recommendations provide guidance for balanced fertilization as it includes micronutrients zinc and boron, and organic inputs in addition to three major nutrients – nitrogen, potassium and phosphorus (NPK). The results of the field trials suggested that the new recommendation could increase rice productivity by 10-30% compared to farmers’ current practice.

Infographic on developing area-specific fertilizer recommendations.

Advocate for approval

A three-day workshop was organized by CIMMYT and NSSRC to mainly share and agree on the recommended fertilizer dosage for rice cultivation and its suitability for achieving the potential yield at the farm level. MoALD Co-Secretary Rajendra Mishra opened the event chaired by NARC’s Director of Crops and Horticulture Research. Workshop participants included MoALD, NARC, Department of Agriculture, USAID Nepal, secretaries from the provincial ministry of land management, soil scientists, university professors, agronomists and other senior government officials.

During the workshop, NSAF explained the application of the QUEFTS model with reference to the case of rice based on field trial data for area-specific fertilizer recommendations. NSSRC soil scientist Shree Prasad Vista summarized the results for rice as an approach and facilitated its endorsement by the MoALD. Participants also discussed strategies for linking up with the extension system to reach large numbers of farmers through the three-tier governments. Fourteen research papers on nutrient management for major cereal crops were also reviewed at the event.

“I commend NARC for this historic work on updating fertilizer recommendations after 46 years. Now we are moving towards sustainable soil fertility management by adopting site-specific fertilizer recommendations,” said MoALD Secretary Govinda Prasad Sharma.

Although the recommendation for rice was an important outcome of the workshop, fertilizer recommendations for other major crops will be made through a similar process.

NARC Executive Director, Deepak Bhandari, said, “We are pleased to move from a comprehensive to a site-specific approach. This is an important milestone for agricultural research in the country and I would like to thank all the scientists, the NSAF project and USAID support for this remarkable achievement.

Similarly, speaking at the event, Jason Seuc, Director of the Office of Economic Growth at USAID Nepal, highlighted the importance of soil fertility management in achieving food security goals set by the government of Nepal. La Seuc noted that sustainable management of soil fertility is essential not only for food security but also to reduce environmental pollution.

Amanda J. Marsh