From Dry Bean Production and Pest management, 2nd Edition
Irrigation Strategy
In many areas of the dry bean growing region, water has become a limited natural resource after having been taken for granted for years.
Dry bean uses less water than some other crops, such as corn.
Dry bean, like most crops, can tolerate some degree of water stress during the growing season without a significant impact on final yield. But several consecutive days of water stress will usually affect yields. So it is important for the grower to understand the basics of irrigation, as well as the relationship between the soil and the plant.
The goal is to use available water supplies to produce a crop as efficiently as possible. Efficient use of irrigation water is important not only to respond to water quantity limitations, but also to protect water quality.
Dry Bean Water Use
Peak water use by dry bean occurs during flowering and pod development in late July and early August at approximately 0.30 inches per day (see graph below). Because the peak water demand for dry bean coincides with the critical growth stages and periods of highest evapotranspiration, the crop is most sensitive to water stress during this time period. Water use rates fluctuate on a daily basis during the growing season. Cool days even during the peak water use period may result in daily water use rates of 0.10 inches per day. Excessively hot periods can increas dry bean plant water use to more than 0.40 inches per day. It is important to effectively schedule irrigations to meet crop demand.
Seasonal water use for dry beans in inches/week and inches/day
Early-Season Water management
It is a common belief that delaying the first irrigation of the season and allowing the crop to experience some stress will not affect yields much. Some people believe that delaying irrigation encourages the plant establish a good root system. And, faced with a limited water supply, some think it is better to irrigate fully late in the season and stress to the crop early than vice versa.
However, research conducted in the Nebraska Panhandle showed that delaying the first irrigation of the season reduced yields by 5 percent for each week of delay for furrow-irrigated fields. For fields irrigated by center pivot, a one-week delay caused a 5 percent yield reduction, but an additional week's delay caused a 15 percent yield drop.
In addition to impacting yield, delaying irrigation also can impact the maturity of the crop. The bottom line is: if irrigation water supplies are limited, avoid stressing the crop at the beginning of the seasonl.
Late-Season Water management
Many growers want to avoid irrigating more than necessary at the end of the growing season in order to save a limited water supply, or to reduce the risk of disease development. At the same time, there is the risk of shutting off irrigation too soon and reducing yield. Research conducted by UNL in the Panhandle compared the effects of shutting off or reducing irrigation water around August 10. When irrigation was limited, yield was reduced by only 1 percent for furrow and 3 percent for sprinkler systems. Yield reduction was more significant when irrigation was stopped altogether around August 10. The reduction was 8 percent for furrow fields and 10 percent for sprinkler-irrigated fields.
From article by C. Dean Yonts
Other UNL Extension Resources:
Predicting the Last Irrigation of the Season, G1871
This NebGuide presents criteria and "rules of thumb" for predicting the last irrigation of the season for corn, grain sorghum, soybeans, and dry beans.
Irrigation Scheduling: Checkbook Method, EC709
Learn how to schedule irrigation based on a checkbook method of water deposits and/or withdrawals.
Managing Furrow Irrigation Systems, G1338
Proper furrow irrigation practices can minimize water application, irrigation costs and chemical leaching and result in higher crop yields.
Minimum Center Pivot Design Capacities in Nebraska, G1851
Factors to consider in choosing an appropriate center pivot design are covered here.
Fundamentals of Surge Irrigation, G1870
Fundamental background for surge irrigation and how it can improve water management is provided in this NebGuide.
Current UNL Research about Dry Bean Irrigation
Impact of Limited Irrigation, and Soil Compaction on Dry Bean Yield and Quality: Because of the prolonged drought and restrictions on irrigation, dry bean growers in western Nebraska have had to modify production practices in recent years. To help growers optimize dry bean production under limited irrigation, UNL evaluated the combined effect of variety selection, irrigation scheduling, and level of soil compaction on dry bean yield and quality. Summary of preliminary results (PDF file, 13 KB)