What is in this article?:
- Orchard floor management in citrus
- Post-emergent weed control
- Orchard floor management options are varied and include: doing nothing, planting a fall cover crop in the middles between tree rows with the possible use of pre-emergent or post-emergent herbicides in the tree row, disking the middles and using pre-emergent and/or post-emergent herbicides in the tree row, or treating the entire orchard floor with post-emergent and/or pre-emergent herbicides.
The objective of an orchard floor maintenance program is to provide conditions for the crop that reduces competition by weeds, reduces danger from frost, allows grower access to the trees for cultural and harvest activities and prevents environmental degradation of agricultural resources like soil and water.
Orchard floor management options are varied and include: doing nothing (usually resulting in a much more expensive weed removal effort later usually involving hoes), planting a fall cover crop in the middles between tree rows with the possible use of pre-emergent or post-emergent herbicides in the tree row, disking the middles and using pre-emergent and/or post-emergent herbicides in the tree row, or treating the entire orchard floor with post-emergent and/or pre-emergent herbicides.
Most citrus growers in the San Joaquin Valley maintain orchard floors relatively free of weeds. Research shows that vegetation on the orchard floor will result in cooler temperatures, and these cooler temperatures may mean the difference between saving and losing the crop. Disked soils have been shown to be cooler than untilled soil, since they conduct heat less efficiently. Firmly-packed bare earth in the middles between rows, wet to a minimum depth of 6 inches, is an efficient absorber of heat during the day and re-radiator of heat to the trees at night. The orchard-floor management system used by most growers consists of applying pre-emergent and post-emergent herbicides tree trunk to tree trunk.
Cover crops are being planted in citrus in areas of the San Joaquin Valley where temperatures do not usually fall much below 30 degrees Fahrenheit, where fruit are picked early before major frost events are likely, or where other concerns outweigh frost danger. Cover crops often have a positive effect on the environment by reducing erosion, reducing runoff through improving rates of water infiltration into the soil, and by reducing the potential of contamination of surface or ground waters that comes from herbicide use.
Herbicide carried in runoff from citrus groves has been shown to be damaging to crops, such as pistachio and grape, located downhill. Research work has shown that swales or drainage areas planted to certain annual crops can provide a buffer reducing runoff from herbicide treated fields. Fall-planted cover crops minimize the amount of vegetation present during the coldest part of the winter. Less vegetation means less frost hazard, but timing planting so that rainfall germinates the seed in the fall can be tricky, especially in the southern San Joaquin Valley. The first rains may not come until temperatures are too low to germinate seed and supplementary water is not usually available since most groves in this area only have low-volume irrigation systems which do not wet areas outside of the tree row. In Kern County most cover crops generally succumb to drought in unirrigated areas of the orchard floor in June. Mowing is used to manage cover crop height in the spring.