MICROIRRIGATION: A SUSTAINABLE TECHNOLOGY FOR CROP INTENSIFICATION AND IMPROVED CROP PRODUCTIVITY

Intensified but sustainable crop production will be a key factor in addressing one of the greatest challenges of this century: feeding 9.5 billion people by the year 2050. Inherent in this challenge are the limitations of arable land as well as a shortage of fresh water sources. Ecologically, crop intensification can protect marginal lands from further development and save water resources. Intensification on a smaller land area also has potential to reduce crop production inputs and crop protection inputs. These include seed, fertilizer, herbicides, pesticides, crop scouting, crop insurance, harvesting costs and any other input cost that has a fixed cost per land area basis. Irrigated agriculture provides about 40% of the world's food supply utilizing approximately 25% of the land resource. Although there was a great expansion of irrigated lands in the 20th century, most experts agree that such additional great expansion in the 21st century will not be possible. The agricultural community must not only increase the food supply, but it must also conserve water and protect water quality. Crop water productivity (CWP, also known as water use efficiency, WUE) is defined as the crop yield divided by the total water used to produce that crop. Thus, it can be easily recognized that either the numerator can be increased, or the denominator can be decreased to increase CWP. Often strategies to increase CWP concentrate on the denominator such as using deficit irrigation to reduce water withdrawals. Implicit with these strategies is the desire to not greatly reduce farm profitability by negatively impacting crop yields to a large extent. There are limitations to using the denominator to increase CWP, since the overall reason irrigation is practiced is to increase farm profitability. It can also be shown that appropriate levels of irrigation can increase CWP. In that aspect, microirrigation (MI) has great potential to intensify crop production at a greater level while still efficiently using water and also protect water quality. Although MI is widely recognized as the most efficient and environmentally friendly method of irrigation, the US and international land area is still relatively low. Slowly, this is changing as water resources are stretched and competition for those supplies increases, more synergistic combinations of crop production technologies are developed, and the sheer need for food production increases. Microirrigation will play a large role in these highly-productive agricultural systems. Efforts such as described in this project W4128 add to our abilities to intensify crop production with microirrigation resulting in more sustainable systems that have less negative impact on the environment. Unless timely action is taken, it is anticipated that water supply- and water quality related crises will affect economies and resources of national and global importance. Microirrigation can reduce the waste of water to a negligible amount and reduce the transport of contaminants to surface water and groundwater. Irrigation events can be fine-tuned to spoon feed water and nutrients just in time to minimize plant water stress. It can optimize crop production (more crop per drop) and in many cases increase the quality of agricultural products.

Methods for Objective 1 (Designs, Technologies and Management Practices)Irrigation system selection, designs, technologies, and management practices are key factors contributing to sustainable use of water resources and increased water productivity. Nearly all participants will make contributions to this Objective, but direct participants will include AL, AZ, CA-UCD, CA-UCR, FL, ID, KS, NE, NM, NY, OK, OR, TN, TX-TAMU, USDA-ARS, WA. This broad group of participants provides a diversity in crop, soil, climate, water availability, and governmental and other constraints. This diversity can foster a more complete and robust conceptual addressing of the 4 key factors in Objective 1.Sub-Objective 1a (Improved System Designs and Irrigation System Comparisons)Alternative irrigation systems are often selected instead of microirrigation systems (MI), although the latter can often make more efficient use of water resources.Sub-Objective 1b (Sensors and Technologies for Improved Microirrigation Management)The use of sensors and other technologies to improve management of MI systems and irrigation scheduling, and to develop precision irrigation schemes/methods is a large focus area of the proposed project involving AL, CA, ID, FL, KS, NE, NM, NY, OK, OR, TN, TX, USDA-ARS, WA. Greater detail on the efforts with regards to irrigation scheduling will be discussed under Objective 2. Management schemes, ultimately for precision microirrigation, using sensors for monitoring and control will be developed and evaluated by CA, KS, NE, NM, NY,OK, OR, TX, and USDA-ARS. These schemes will range from simple information delivery for decision support to more fully autonomous systems that can be overridden by the enduser should conditions warrant. As an example CA and NY are working on evaluating electronic tensiometers with an extended range of operation (greater than typical 1 bar). This effort will be discussed more under Objective 2. On the other end of the spectrum, CA, KS, OR, TX, and USDA-ARS will be evaluating more fully autonomous irrigation management systems. As this is a rapidly emerging research topic, it is anticipated that these results will inform future research decisions. Application of UAVs and remote sensing will be focus areas for AL, KS, and USDA-ARS. There are also large technology transfer efforts to disseminate sensor technologies to producers in AL, CA, FL, ID, KS, NE, NM, OK, TN, TX, and WA.Sub-Objective 1c (Nutrient Management Schemes and Technologies for Microirrigation)Optimizing crop water productivity under irrigation system requires careful attention to nutrient management. However, MI systems are well suited to applying nutrients both in a spatial (e.g. near plant roots with less off-site movement) and temporal (just-in-time while minimizing excesses or shortages) contexts. Crop water productivity is increased by having the nutrients optimized in both the spatial and temporal sense. Many, if not all of the W4128 participants will utilize precise nutrient management to increase crop yields, improve water productivity, as well as increase sustainability of agriculture systems through minimizing contamination and pollution. Nutrient management technologies, procedures and strategies for higher-value fruit, vegetable, tree and vine crops are often more complex than those of lower-valued grain, fiber and oil seed crops, but many of the technologies can be economically scaled or adapted to the pertinent crop. CA-UCD, CA-UCR, FL, OR, TN, USDA-ARS, WA will focus some irrigation and nutrient management research on these higher value crops while KS, NE, NM, OK, OR, and WA will conduct similar types of studies with lower value or commodity crops. Modeling efforts by CA-UCR, CA-UCD and NM will augment and extend the results from these studies.Methods for Objective 2 (Irrigation Scheduling)Irrigation scheduling based on ET, Soil, Plant, or combined methods will be an integral part of the research conducted by essentially all project participants.Sub-Objective 2a (Weather or ET-Based Irrigation Scheduling)Several of the participants (CA-UCD, FL, KS, OK, TX-PVAMU, TX-TAMU, WA, and USDA-ARS) have/shared active weather and ET networks and also have and support weather based irrigation scheduling software.Sub-Objective 2b (Soil-Based Irrigation Scheduling and Sensor Evaluation)ID, KS, NM, OK, TX-TAMU, TX-PVAMU, WA, and USDA-ARS will have a strong focus on soil-based approaches as well as the evaluation, calibration, and/or development of sensors and electronic logging systems. Crops studied will include legume and grain cover crops, row crops (leafy greens, okra, tomato, and strawberry), cereals, tree crops, wine grapes, and halophytes irrigated with brackish water. Tests will include calibration of soil moisture sensors in soil amended with different amendment types and rates, and comparison of soil sensor accuracy for soil moisture, soil temperature and soil salinity. Commercial soil moisture sensors will also be used as part of a recently developed prototype automated irrigation scheduling package. Experiments will be performed on experiment station lands and in grower cooperator fields, and all information will be extended to the respective industry clientele, including grower feedback regarding level of satisfaction, convenience and perceived value of the sensors an approaches tested.Methods for Objective 4 (Technology Transfer)Another important focus of the project includes development and adaptation of technology transfer products for a diversity of stakeholders. All project participants will have some involvement in technology transfer, whether directly through cooperative extension or more indirectly through publications and presentations. Efforts will focus on four primary activities: development and expansion of internet-based resources, decision tools and applications; development of print and multimedia content; coordination of educational events; and advancement and promotion of microirrigation through public-private partnerships.A variety of outreach strategies will be used to reach diverse audiences. Traditional extension/technology transfer methods (print and electronic fact sheets; field days; presentations at meetings for agricultural and horticultural producers; training events for county extension agents; Continuing Education Units (CEU) opportunities for irrigation professionals and crop advisors, mass media, technical sessions at conferences) will be complemented with newer/emerging methods (social media, YouTube, Twitter, and others) to reach traditional and emerging audiences. Multi-state/multi-institution (USDA-ARS, TX, KS, OK, OR) products (publications, field days, etc.) will reinforce the collaborative nature of the project, and they will promote consistent messaging of the educational efforts.