Simulated crop provides answer to irrigation issues

South Asia has witnessed a rapid growth in rice and wheat production that has defined the Green Revolution there. During the past 30 years, the Indian Punjab has transformed its agriculture through new technology that provides for high-producing plants, increased fertilization, and irrigation. Rice and wheat production has more than doubled with an increase in farmed areas, totaling about 6.4 million acres of rice and 8.4 million acres of wheat.

While the Indian Punjab’s agricultural performance continues to be impressive, evidence suggests that it’s coming at a price: their groundwater use is becoming increasingly dangerous to the environment. In some areas, the water quality is worsening as water tables decline. In other areas, water is flooding the soil making it difficult for plant growth. The rampant use of irrigation is encouraged by cheap water policies that provide producers with little or no expense for water use.

Since irrigation water charges are extremely cheap, farmers seem to use it more excessively and inefficiently. They are able to raise crop yields but at the cost of extremely low water quality. It is used this way due to crop decisions farmers must make for their crops before knowing the weather conditions for the upcoming season. Irrigation provides a way around these weather misjudgments. Farmers can adjust the amount of water coming to their crops by irrigation to supplement the precipitation levels.

In response to this dilemma, scientists at Oklahoma State University, the Punjab Agricultural University, and Texas A&M have investigated the use of alternative cropping systems to reduce irrigation water use and improve environmental conditions in a study funded by the United Nations Development Program (UNDP). A simulation model was used (CropMan) to assess the biological structures, processes and economic practicality of an alternative range of cropping systems. Crops that were studied included maize, cotton, sorghum, soybeans, and mustard. Results from this research were published in the July-August 2007 issue of Agronomy Journal.

The scientists gathered agronomic, geographic, and climatic data of the Punjab region. The data was entered into the simulation model and was adjusted for known farming conditions. Irrigation water response functions were estimated for each of the cropping systems, which showed how crop yields responded to alternative types of irrigation water strategies. Simulations assessed how irrigation water pricing affects the choice of cropping patterns among producers in the Indian Punjab.

The study found that two of the alternative crops, cotton and soybean, would enter cropping patterns provided that irrigation water prices moved to about 25% of the price charged by municipal water authorities in large cities such as New Delhi. Shifting cropping patterns toward more water-efficient enterprises would decrease irrigation water use on a typical rice field by nearly 66%. Charging producers for their irrigation water use was found to have only a modest effect on farm income. According to the research, once farmers have to pay for the water that irrigates their crops, they will use much less, but much more efficiently. This will subdue much of the potential environmental damage and reverse downward trends.

Research is ongoing at Punjab Agricultural University to field test alternative cropping systems across a range of irrigation management strategies. Additional field testing is planned to determine how the alternative crops would perform under actual farming conditions. Further research is needed to assess the environmental benefits that would accompany the increased water efficient cropping patterns found in this study, as well as to determine the most socially accepted water pricing for Punjabi farmers.