Site-specific nutrient management sees increases in rice yields

A team of scientists at Punjab Agricultural University, the International Rice Research Institute (IRRI), and Virginia Tech have been successful in increasing average rice yields in northwest India using site-specific nutrient management strategies. The research results show that targeted interventions can achieve increased yields needed to feed growing populations. It also indicates that even in a region where the 'Green Revolution' has already transformed agriculture and made it highly efficient, gradual increments are still possible. The research results are published as an open access article in the November-December 2007 issue of Agronomy Journal.

The findings can be immediately linked to the situation in Africa, where the revolution still has to begin and where rice production is increasing gradually (for recent examples of what the most basic of interventions, the application of fertilizer, can achieve, see the story about Malawi's super-harvest and its transformation from being a begging bowl to becoming a net food exporter supplying the World Food Program, here; and research results from trials amongst smallholders in Zimbabwe, here). The continent holds by far the largest potential for the production of sustainable bioenergy (that is, producing energy after meeting all food, fiber, fodder and forest product needs of growing populations and without deforestation). If African farmers adopt basic 'Green Revolution' agricultural methods, the continent's exportable bioenergy potential is estimated to be around 350 Exajoules of energy by 2050, or roughly 2.5 times the energy contained in the world's total current oil consumption.

When this transition to modern agriculture is made - and last year, 500 scientists called for the switch at the African Fertilizer Summit - Africa too can refine its nutrient management strategies and traverse to precision farming, as is being done in the Punjab trials. Later, more technology-intensive challenges can be addressed, such as improving the photosynthetic efficiency of plants, developing dedicated energy crops with specific bioconversion characteristics, or managing large integrated carbon negative bioenergy systems relying on biochar or geosequestration.

But let us look at the achievements in the Punjab province. Nowadays the region accounts for 10 percent of the Indian rice production and is currently witnessing a slower rice grain yield growth rate as compared to the spectacular yield growth rate witnessed during the Green Revolution phase (1960-1986). To meet the expected food demand in the next 30 years, rough estimates for India suggest the need to increase the average farm productivity of the system, which is currently at 45 to 60% of the attainable yield potential, to 70 to 80% of the attainable potential.

The researchers hypothesized that decreased nutrient supply capacity of soil and improper nutrient management approaches were key factors in the slower growth rate. By analyzing the existing soil nutrient composition and applying site-specific nutrient management (SSNM) the scientists were able to increase average rice grain yields by 17 percent compared with current farmers' fertilizer practice. Similarly, profits rose about 14 percent using SSNM.

Over a two year period the scientists applied calculated amounts of nutrients at 56 sites in six key irrigated rice-wheat regions to evaluate the effectiveness of SSNM in increasing yield growth rates. Using the 'Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS)' model, which predicts crop yields from chemical soil characteristics, the scientists refined their nutrient applications and schedules on a site-specific basis:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: food :: fertilizer :: rice :: agronomy :: Punjab ::

In addition to yield and profit increases, improved timing of fertilizer applications led to a measured 13 to 15 percent increases in plant accumulations of nitrogen, phosphorous and potassium.

Site-specific nutrient management, as defined in our study, has potential for improving yields, profit, and nitrogen use efficiency in irrigated, transplanted rice. Future research needs to build on the present SSNM approach to develop a more practical approach for achieving similar benefits across large areas without farm-specific modeling and with minimum crop monitoring. - Harmandeep Singh Khurana, lead author

While further yield increases are likely to occur in small, incremental steps that involve gradual buildup of soil fertility and fine-tuning of crop management, the authors conclude that the agronomic and economic successes of SSNM are due to its site-specific and dynamic nature which take soil variability into account. They suggest that the major challenges for SSNM will be to reduce the complexity of the technology as it is disseminated to farmers and to combat environmental pollution stemming from nutrient leaching and runoff from rice fields.

The International Rice Research Institute (IRRI) is the oldest and largest international agricultural research institute in Asia. It is an autonomous, nonprofit rice research and training organization with staff based in 14 countries in Asia and Africa. It played a key role in the Green Revolution.

References:
Harmandeep S. Khuranaa, Steven B. Phillips, Bijay-Singh, Achim Dobermann, Ajmer S. Sidhu, Yadvinder-Singh and Shaobing Peng, "Performance of Site-Specific Nutrient Management for Irrigated, Transplanted Rice in Northwest India", Agron J 99:1436-1447 (2007), DOI: 10.2134/agronj2006.0283.

American Society of Agronomy: Site-specific nutrient management sees increases in rice yields - December 10, 2007.

Biopact: Malawi's super harvest proves biofuel critics wrong - or, how to beat hunger and produce more oil than OPEC - December 04, 2007

Biopact: Fertilizers boost crop production amongst smallholders in Zimbabwe - April 13, 2007