Nakayama Research Professorship - Shukla

Problem 1: Severe shortage of water for irrigation

New Mexico is facing a severe shortage of surface water for irrigation and the problem is getting worse with continued drought. Some people believe that this is a ten year drought cycle; however, there is a general consensus that the drought situation is not going to improve in the near future. Water shortage is putting increasing pressure on the groundwater resources. New Mexico groundwater aquifers are not contiguous. Drip irrigation with high application efficiency is important for water conservation, however, there is a need to move beyond drip and focus on where the drip emitters should be placed for better water utilization.

Water saving, productivity, and quality of chile pepper cultivar, (NuMex Joe E. Parker) were evaluated under compensated and uncompensated treatments. Three drip irrigated treatments were used (1) control; where water was applied at the surface using two drip emitters, (2) partial rootzone drying vertically (PRDv); where subsurface irrigation was applied at 20 cm depth than usual 10 cm depth, and (3) partial rootzone drying compartment (PRDc); where roots were divided into two compartments and irrigation was applied to one of the compartments on every alternate day cycle for 15 days. This study showed that both PRD could save as much as 30% of water without significant yield reductions. Water use efficiency increased by up to 31% under drip irrigated PRD treatments. No differences in photosynthetic rates and stomatal conductance among different treatments suggested that chile plants under PRDv and PRDc compensated for water stress in one part of the vertical or lateral root zone profile by taking up more water from the less-stressed parts of the root zone to meet their ET demands. This research demonstrated the compensation mechanism that is operative by the roots in which they extract more water from water available part to compensate for the reduced water uptake from drier rootzone. This research should be repeated on a field scale for chile and other specialty crops of the state. Research and demonstration plots should be established in Leyendecker and/or Fabien Garcia Science Centers to encourage grower's participation. Further efforts include collaboration with other faculty members to identify genetic markers or plant hormone for chile produced under water stress, and determination of change in abscisic acid content and capsaicin content for chile quality due to water stress (drought).

Problem 2: Saline groundwater for irrigation

"The cure for everything is salt water- sweat, tears, or the sea" (Isak Dinesen). Isak was not a hydrologist otherwise he would have also added groundwater aquifer to the proverb. Irrigation water salinity is an important abiotic factor that can threaten the survival of agriculture in the southern New Mexico. The groundwater aquifers are of varying thickness and quality. At present there is no information available on how, how much, and at what depth salt accumulation will occur due to saline water application? How will it influence pore clogging and water movement? How much water will be required to push salts below rootzone? And how much yield reductions can be expected using saline water? At present, there is scant information available on the actual crop ET and crop coefficients for irrigation using saline water, as well as on threshold salinity levels, knowledge of which is extremely important for efficient irrigation scheduling with low quality water to sustain production in arid areas. A new project is designed to evaluate effects of water and salinity stresses on yield and quality of some of the specialty crops of New Mexico, namely chile and onion. This project involves various soil, plant and micrometeorology measurements to determine the actual crop ET, crop coefficients and leaching fractions, and threshold salinity level for sustaining production, and quantify pore-clogging due to saline water application. This is an important research started with the support of graduate research award of agricultural experiment station Director, and must be continued for the survival of agriculture in the southern New Mexico. Genetic mapping and other drought indicators can be identified in collaboration with other faculty members.

Problem 3: Groundwater for drinking and irrigation: Augmenting water portfolio or irrigation

The arid areas of the world including southern New Mexico are facing severe water shortage and utilization of groundwater for irrigation is fast increasing. Brackish groundwater can be purified using reverse osmosis. Sustainable management of the highly saline concentrate resulting from reverse osmosis and other processes is a major environmental problem that limits widespread implementation of inland groundwater desalination in New Mexico and the southwestern U.S. However, only scant information is available with regard to the transport mechanism of concentrate and growth and survival of vegetation under continued concentrate application. Interest in land application as a cost-effective treatment system for wastewater has increased, and focuses on land-applied effluents as a beneficial resource for soil and vegetation rather than as a wastewater "disposal" issue. There is a mighty need of expanding water portfolio by including treated municipal, industrial, dairy, and produced water for irrigation. A new cropping pattern model needs to be developed by including water across various salinity gradient for sustaining agriculture, vegetation and air quality of arid area.

The project (described under Problem 2) on establishing threshold salinity levels for various specialty crops will serve as a guideline for desalinization of well water. We are also currently working on screening growth potential of helophytes irrigated with saline groundwater and concentrate from reverse osmosis. The salinity of the concentrate can be controlled during RO process. I propose that the salinity of the concentrate generated from the reverse osmosis will be based upon specific crop's salinity tolerance. Thus quality of both drinking water and irrigation water can be managed based upon the type of crop, stage of the crop and the salinity thresholds. Land application of desalinization bi-product would comprise a novel anthropogenic disturbance to natural vegetation communities. Sustainable desalinization concentrate management will ensure that concentrate accumulation "if any" takes place at deeper depths and does not cause vegetation damage and there is no likelihood of leaching to the groundwater. Unless the climate predictions are reversed, this project is important for the survival of agriculture and people in the southern New Mexico.