When is nitrogen fertilization of alfalfa beneficial? Almost never!
Nitrogen (N) fertilizer is generally not required for alfalfa production since alfalfa can obtain its own N from N-fixing nodules (Figure 1). Alfalfa fixes most (70-90%) of its N needs from the air through Rhizobium bacteria residing in alfalfa root nodules (Figure 1). Since 78% of our air consists of nitrogen gas, this supply of ‘free fertilizer' is inexhaustible. A recent unpublished UC Davis-CSU Fresno study showed 90% of N in alfalfa originated from the atmosphere -- but less when soil N levels were high, for example, in manured fields.
Although there have been some reports of yield and forage quality...
- Author: Vonny M. Barlow
- Author: Eric T. Natwick
Of all of the insecticides evaluated against blue alfalfa aphid (BAA) by Eric Natwick of Imperial County, almost every insecticide applied to alfalfa this spring gave initial knockdown of BAA. Blue alfalfa aphid populations resurged in 7-10 days. Treatments giving 70–75% control (reported by PCA’s) were combinations of a pyrethroid with an organophosphate.
Possible factors for our BAA issue:
- High initial aphid populations
- Smaller than expected populations of predators and parasites; particularly the seven-spotted lady beetle
May be weather related or pesticide...
- Author: Carol A Frate
Many of us think about too much water killing alfalfa during the hot days of summer. And this does happen, especially at the tail end of fields where water may collect and stand for hours after the irrigation has ended. When temperatures are over 100 oF and the soil is saturated for extended periods, roots can essentially suffocate due to lack of oxygen. Plants die very quickly and roots begin to disintegrate. Because the root zone is usually saturated from the soil surface for a depth of several inches or even feet, the entire root rots. This situation is referred to as “scald” and is a physiological process rather than a pathology process.
There is another situation where saturated soil leads...
- Author: Vonny M. Barlow
The alfalfa weevil complex, comprised of the Egyptian alfalfa weevil, Hypera brunneipennis, and alfalfa weevil, Hypera postica, is the most damaging arthropod complex in California alfalfa (Medicago sativa). If populations of alfalfa weevil are left unchecked, the larvae can cause severe defoliation, significantly reducing yields. Repeated use of insecticides such as organophosphates and carbamates has resulted in these insecticides being detected in surface waters, providing incentives to find alternative means to manage this pest. The alfalfa weevil is susceptible to the biological control agent Bathyplectes curculionis in many alfalfa-growing regions in the United States. Work...
- Author: Peter B Goodell
The UC Statewide IPM Program has announced the availability of an on-line tutorial to aid in the use of Year Round IPM Programs.
Year Round IPM Programs were developed as another means to retrieve information from the comprehensive Pest...