Submitted to: Almond Industry Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/22/2003
Publication Date: 12/1/2003
Citation: Holtz, B., Mckenry, M., Caesar, T., Caesar, A.J. 2003. Benefits of Chipping Almond Brush. In: Proceedings of the 31st Almond Industry Conference, December 3-4, 2003, Modesto, California. 31:164-168.
Interpretive Summary: Using almond prunings as a soil amendment, rather than burning them, as practiced prior to the institution of air quality rules in California, is assessed for effects on the fertility and health or quality of the orchard soil. The availability of some nutrients for plant growth such as nitrogen were lowered in the first year (compared to soils not receiving the chips) after adding the almond chips to the soil, while potassium was increased. In the second year, nitrogen was not lower, zinc was, and potassium and phosphorous were higher. In the first year after amendment, organic matter as expected from adding plant material, was higher, nitrogen in the form of ammonia was higher, and the ability of the soil to retain nutrients without readily having them washed away (expected with higher organic matter), and the overall fertility of the soil were higher. In the second year, overall nutrient levels were similar, while the nutrient retaining potential of the soil was lower. In the first year after adding chips levels of a plant parasitic nematode Criconemella were lower and bacteria-eating nematode such as Bunonema and such fungal and bacterial eating nematodes as Dorylaimida. Mushroom type fungi, living as filaments in the soil were found at higher densities when soils were chipped and the soil structure as indicated by the size of soil aggregates (an effect of the filaments of the mushroom type fungi) was better, and this effect was especially true when chipped soils had not been disturbed through cultivation.
Technical Abstract: The wood chipping of almond (Prunus dulcis) prunings could provide an alternative to burning that would not contribute to air pollution and add valuable organic matter to soils. The success of wood chipping depends on whether the wood chips deplete the soil of critical nutrients necessary for tree growth. An experiment was established whereby wood chips were mixed with soil and placed in containers, each with an almond tree, in order to quantitatively examine the effect of wood chips on soil nutrients, soil aggregation and the rhizosphere microbial community. Control trees were planted in containers without wood chips. Tissue analysis was performed on leaf petioles to determine whether the wood chips had an effect on nutrient availability. After the first year, trees growing with wood chips had less N, Zn and Mn while P was increased. After the second year, trees with wood chips no longer had lower levels of N while P and K were significantly increased, but Zn was lower. Soil analysis after the first year showed significantly higher levels of Ca, Mg, Zn, Cu, P and K with wood chips. The percent carbon, NH4-N, cation exchange capacity (CEC), electrical conductivity (EC) and the percent organic matter (OM) were increased. The soil pH and N03-N levels were lower. Similar results were obtained the second year, except that Mn and Fe levels were lower in wood-chipped soils while B and Na were increased. The CEC was no longer higher in wood-chipped soils. When nematode populations were assayed after the first year there were fewer Criconemella and more Bunonema, Dorylaimida and free-living bacterial and fungal feeding nematodes in wood-chipped soils. Similar results were obtained after the second year except that root lesion was reduced in wood-chipped soils. More basidiomycetes were counted in wood-chipped soils and detected at higher levels with ELISA. Larger soil aggregates were found in wood-chipped soils. Undisturbed wood-chipped soils had more soil aggregates than disturbed wood-chipped soils.