Maintaining orchard soil health is a fundamental priority of profitable walnut growers. Good tilth and optimal organic matter content receive constant attention.
The California Walnut Board’s research funding commitment to IPM (e.g. alternatives to soil fumigation, disease resistant rootstocks that don’t require pesticide protection, reduced pesticide sprays) has beneficially protected the soil biosphere.
- Cultivation: Ongoing cultivation lessens soil fertility. Selective herbicides are used in California walnut orchards as growers increasingly use non or minimum tillage programs to enhance soil tilth, reduce costs, and minimize dust (see Fig. 9).
Fig. 9. Herbicide treated, non-cultivated walnut orchard using a double line drip irrigation system.
- Organic Matter: California walnut growers recognize optimal levels of soil organic matter encourage a healthy root biosphere that includes both micro and macro organisms. There is considerable effort to preserve and increase organic matter, reduce weeds, and to reduce erosion in California walnut orchards through use of cover crops (See Fig. 10), shredding pruning’s (see Fig. 5), and use of composts and manures. Organic matter coincidently improves soil tilth including its water and nutrient holding capacity.
Fig. 10. Cover cropped walnut orchard