Influence of soil mixing and sterilization on growth and nutrient uptake of black walnut seedlings

Abstract

Abstract The effects of soil mixing (disturbance) and sterilization on nutrient solubility and uptake, and on growth of potted black walnut seedlings in forest and field soils were studied under glasshouse conditions. Seedlings were grown for 16 weeks in soils that were either disturbed or undisturbed only, and in combination with two methods of sterilization. Both pre‐ and post‐harvest soil data showed that the forest soil had higher concentrations of all elements tested (except Mg) than the field soil. With the exception of Ca in the field soil, both disturbed forest and field soils had higher concentrations of P, K, Ca, Mg and Mn than undisturbed soils. The effects of sterilization on extractable nutrients were variable, with higher amounts resulting from the autoclave treatment. Foliar concentrations of N, P, and Ca in seedlings grown in disturbed forest and field soils were higher than for other treatments. Nutrient concentrations were usually higher in seedlings grown in autoclaved than in fumigated soil. Soil disturbance increased seedling height growth in field but not in forest soil. Apparently the reduction of field soil bulk density is important in increasing the growth of black walnut. Much interest exists in growing black walnut (Juglans nigra L.) on abandoned farm land. However, walnut usually grows slower on abandoned fields than on cleared forest or old fields invaded by brushy vegetation18, 4. This is because on many old fields cultivation has compacted the soil, increasing the bulk, density12 and lowered fertility, tloreover, old fields harbor many plant pathogens and potential symbionts not found in forest soils2. Both conditions can be alleviated, however. By tilling compacted field soil water infiltration can be increased and plant rooting patterns changed6 16. And soil‐borne organisms can be controlled by sterilizing with steam or fumigants. However, sterilization not only kills pathogens and insect pests, but may also affect development of mycorrhizae and chemical properties of soils1 10, 15. Soil tillage and sterilization are commonly used in agriculture and horticulture and may help in establishing tree plantations. So, we undertook to evaluate the effects of soil mixing (disturbance) and sterilization (fumigation and autoclaving) on nutrient status of forest and field soils and on growth and nutrient uptake by black walnut seedlings potted in these soils.