THE EFFECT OF ORGANIC AND INORGANIC MULCHES ON SOIL ENVIRONMENT, ROOT DEVELOPMENT AND NUTRIENT UPTAKE OF MATURE APPLE TREES

In tree fruit crop production, amelioration after planting with biological agents is still a contentious topic. The organic material cannot be incorporated in the soil after planting, because it will damage the tree root system. If it is applied on top of the soil, the contribution to soil biology is questionable and has indeed been reported as such by various authors. Nevertheless, we need to improve soil biology to maintain high yields, not sustainable with an ever increasing chemical fertilizer application only approach, and we need to achieve this without major physical interference with the root zone.
Our research is aimed at investigating possible effects of biological and an inorganic mulch on top of the soil in an established ‘Cripps’ Pink’ apple orchard on a sandy loam soil. A woven, black poly-geotextile PT110 was chosen as the inorganic mulch. The control received no mulch and the rest of the treatments comprised wood chips, compost, and a thin wood chip layer on top of a thin vermi-compost application. The standard orchard practices for fertilization, irrigation and pest management were followed. The main emphasis was to quantify the effects of the soil biology, soil environment and root distribution on nutrient uptake and distribution in especially the fruit, to improve fruit quality.
Soil environment was quantified in terms of micro- and macro-elements and soil temperature. The wood chips increased K and Na, whereas the vermi-compost increased Mg and K. Mulches changed the minimum temperature in the top 50 mm by 1°C, and as much as 5°C for maximum temperature during summer.
A destructive root study showed that roots with diameter less than 2 mm comprised the bulk (average 75%) of the total root volume in all treatments. The top 100 mm also contained the highest percentage of roots smaller than 2 mm. Mycorrhiza studies indicate a significant increase in colonization between the control and mulches for the sandy loam site. Preliminary nematode results showed that all organic mulches decreased the percentage of pathogenic nematodes from 2009 to 2010.