How to Manage Pests
UC Pest Management Guidelines
(Reviewed 12/08, updated 12/08)
In this Guideline:
Frequency of crop irrigation depends upon plant growth, root development, water-holding capacity of the soil, and the water use through evapotranspiration. Compared to other crops, beans have a relatively poor root system. About one month after planting, when visual signs of moisture stress are first noted, bean plants typically have removed about 50% of the available soil moisture from the 6 to 12 inch depth, but at 3 feet, only about 10%. Baby limas and blackeyes have the best root systems while early pinks are better than red kidney.
Research and production experience have shown that common beans grown in the San Joaquin and Sacramento valleys on loam soils will require frequent but light irrigation every 6 to 8 days. In coastal areas, 14- to 18-day irrigation intervals are common. Consumptive use (evapotranspiration) of common beans ranges from 20 to 25 inches per season, depending upon the variety and production area of the state. Consumptive use is the amount of water that evaporates from the soil plus the amount transpired by the bean plants. It does not include the loss of water from head-ditch seepage and evaporation or the tail-water loss. Therefore, depending upon the efficiency of the irrigation system, the amount of water needed will range from 25 to 40 inches per year.
Summer beans are irrigated in a number of ways in California. For most common beans, large limas, and bush baby limas, furrow irrigation is the usual method, but sprinklers are popular in some areas of the state, especially on shallow soils or soils high in clay content. Most vine baby lima beans in the Sutter Basin of Sacramento Valley are subirrigated using perimeter ditches. Subirrigation is also practiced for lima production in the Delta region. However, because common beans have a poor root system compared to limas, they are usually not subirrigated.
The foliage of common bean plants darkens in color when moisture stressed; however, when water is applied, the color will lighten. The difference in plant color is readily seen between irrigated and non-irrigated areas. If bean plants are moisture-stressed, lower leaves, flowers, and small pods may drop. If common beans are severely water stressed during the growing season, yields will be lower as will quality, because the weakened plants may not be able to recover.
Another approach to irrigating on clay soils is to form furrows on 60-inch centers, and shape the beds flat on top. Use a bed that is wider than the conventional 30 or 40 inch width. Plant beans in rows of 28 to 30 inches apart. Make irrigation runs 600 to 800 feet long, if possible, and no longer than 1,200 feet. Using wider beds leaves an area on the bed unsaturated, thereby allowing oxygen to remain in the soil for roots. This wide-bed system has no practical application on loamy soils and should not be used on silty soils where water penetration is a problem.
Soils with a high silt content present another challenge to growing common beans. These soils absorb moisture well after a cultivation, but after a few irrigations, they seal and become almost impervious to water penetration. After the bean plants close over the row, cultivating equipment cannot be driven in the fields. A good sprinkler system works well in supplying water to beans grown on problem soils.
UC IPM Pest Management Guidelines:
W. M. Canevari, UC Cooperative Extension, San Joaquin County