ANNUAL REPORT OF WESTERN REGIONAL PROJECT W-128

Supported by Allotments of Regional Research Funds

Hatch Act, as amended August 1955

January 1 to December 31, 1998

Project: Microirrigation: Management Practices to Sustain Water Quality and Agricultural Productivity (January 1 to December 31, 1998)

Cooperating Agencies and Principal Leaders:

State Agricultural Experiment Stations
Arizona AZ M. Yitayew*, A. W. Warrick, T. L. Thompson
California CA K. A. Shackel*, D. J. Hills, L. J. Schwankl
Colorado CO I. Broner*
Florida FL C. Stanley*
Guam GU P. Singh*
Hawaii HI I. P. Wu*
Idaho ID H. Neibling*, T. A. Tendall, R. H. Brooks, B. A. King
Iowa IA H. Taber*
Kansas KS F. R. Lamm*, G. A. Clark
Michigan MI R. von Bernuth*
Minnesota MN S. Gupta*, J. F. Moncrief, C. Rosen, J. Waddell
Oregon OR R. Roseberg*,
New Mexico NM T. Sammis*
Texas TX B. Lesikar *, R. D. Lacewell, J. Moore, M. J. McFarland,
Virginia VA N. Powell*
Washington WA R. G. Evans*, A.S. Felsot, R. L. Wample, W. W. Cone
Wyoming WY R. Zhang*
USDA-ARS WMRL CA J. Ayars*

* Voting Members

Officers in 1998

H. G. Taber, IA Chair
H. Neibling, ID Vice-Chair
M. Yitayew, AZ Secretary
B. Lesikar, ID In-coming secretary

I. PROGRESS OF THE WORK AND PRINCIPAL ACCOMPLISHMENTS

Objective 1. Development of microirrigation system BMPs to sustain crop production and minimize water application and water quality degradation.

States reporting activity: AZ, CA, FL, GU, HI, IA, KS, VA, WA

Summary: States are fine tuning the BMPs for microirrigation, concentrating on scheduling approaches, and adapting microirrigation to current environmental problems .

AZ compared furrow and subsurface irrigation systems at water amounts of 50 to 125% of the AZSCHED prescribed amounts for corn production. There was no difference in yield between systems, but there was significance in water amounts for yield. The crop coefficient curve in the computer model AZSCHED did not accurately represent crop coefficient estimated from field data. CA studied the effect of pear graft union on tree water flow and found that hydraulic restriction at the graft union was not a source of water stress. Water stress did develop as a result of restricted water flow across all or part of the root system. Improvement in health of the root system may lead to improved water availability and less need for applied N. FL found that movement of nitrate-N through the soil of citrus groves varies with the time of year. For the rainy summer and early fall, soil water movement was greatest at the drip-line and in-row middles while during dry periods (winter and early spring), movement was greatest beneath the citrus canopy near the microsprinkler due to irrigation. GUAM developed a irrigation schedule for head cabbage to minimize deep percolation. HI developed data for scheduling of a high uniformity designed microirrigation system to achieve optimum performance for yield, quality, and to minimize deep seepage. IA evaluated several irrigation scheduling systems for irrigating sweet corn. KS found that, with remediation, livestock wastewater can be used in a SDI system. Also, a SDI system was evaluated for applying water to winter wheat. VA continued work on SDI of corn, cotton, peanut, soybean, and sweet corn. WA found that an application of insecticides in the microirrigation system for hops was as effective as foliar application with the advantage of reduced rates.

Objective 2. Carry out field evaluation of BMPs for crop production and water quality degradation control using microirrigation.

States reporting activity: AZ, CA, FL, IA, KS, NM, TX, WA, WY

AZ evaluated 2 permeameters for measuring subsurface unsaturated hydraulic conductivity, nylon cloth and ceramic cup. The nylon cloth was not effective, but the ceramic cup provided good hydraulic coupling when fine sand was used between cup and soil. CA evaluated stem water potential for water application with almond trees. FL developed field data used to evaluate LEACHEM to predict solute movement in a citrus grove. IA evaluated soil moisture tension devices on two soil types for usefulness in scheduling irrigation. KS made presentations to state and regional groups concerning BMPs for n fertilization for corn using SDI. NM evaluated the water balance method for onion irrigation scheduling. TX developed a demonstration project with SDI of wastewater across five different soil types. WA evaluated pesticide movement with hops using soil moisture sensors for irrigation control. WY compared sprinkler, furrow, and drip irrigation methodology for dry land sugar beet production.

Objective 3. Develop an expert system and models for chemical management practices using microirrigation systems.

States reporting activity: AZ, CA, KS, MN, WA, WY

AZ provided data on hydraulic conductivity useful for modeling soil transport of water and dissolved solutes. CA developed a model to simulate effects of emitter clogging. Found that the pump pressure head value and manifold pressure head profile need to be monitored for successful detection. KS continued work on the final development of a drip tube performance reporting standard. MN refined the SIMPOTATO model for soil regions with irrigation available for world potato production. WA provided input data for hops to model pesticide movement. WY used the CHAIN-Ir model to simulate water flow, movement of chemicals in saturated soils, and root uptake for sugar beet production.

Objective 4. Assess the economics of BMPs developed for microirrigation systems.

States reporting activity: HI, WA

HI has developed a well designed irrigation scheduling system to include economic factors of environmental pollution, water cost, and price of yield. WA provided input data on economics of managing chemigation for hops.

II. Usefulness of Findings

Many useful findings are related in Section I. Here are some additional highlights.

AZ Development of reliable and accurate methods to measure or estimate hydraulic conductivity is vital to modeling efforts.

CA Plant water stress measurements hold promise for scheduling irrigations resulting in significant water savings without negative impacts on tree yield.

FL Soil moisture content under citrus canopy depends on the season of the year and affects irrigation scheduling and quantity.

GU Location of tensiometers for irrigating head cabbage is very important in scheduling water quantity.

HI Design criteria for microirrigation were developed from considerations of water, yield, environmental protection and total economic return.

IA Soil moisture tension devices for scheduling irrigation may be site specific.

KS SDI systems can be operated during winter months under freezing conditions permitting year-round application of wastewater sources and minimizing on-site winter storage requirements for wastewater. However, winter applications of water from a SDI system may leach beneficial crop nutrients out of the irrigated sol zone.

NM Microirrigation can be used to increase yields but under sandy loam soil type irrigation efficiency will be low to achieve maximum yield.

WA Application of systemic insecticides by SDI chemigation is ideally suited for IPM programs since insecticides can be targeted only to feeding pests, leaving predators populations unharmed.

WY Microirrigation, compared to flood and sprinkler, resulted in less water applied to the soil system resulted in a lower amount and slower movement of nitrate out of the rootzone towards groundwater.

III. Work Planned for 1999.

The principal efforts in 1999 will be preparing publications documenting the BMPs . Special effort will be made to put a simple scheduling model on the internet. The modeling efforts will continue and intensify particularly in regards to the soil physical models and their evaluation. Continued evaluation of SDI with additional crops and more intensive soil and plant nutritional analyses will be conducted to refine BMPs. Research in progress will be continued such as evaluation of soil moisture devices, deep seepage water quality, effect of wastewater on soil hydraulic conductivity, and the potential differences in root health and effects on tree water stress.