Effect of soil management and water stress upon growth and cropping of the highbush blueberry

The field trial on 'Bluecrop' highbush blueberry, planted in 1986 on a podsolic sandy soil, was carried out in 1987-1995. The effect of six fertilizer treatments: (control, P, N+K+Mg, N+K+Mg, N+P+K+Mg, N+P+Mg, N+P+K, was compared in split-plot factorial design, for two soil management systems (clean cultivation and bark mulch) in sub-blocks. Terminal growth, size of bushes, yield and quality of berries were recorded. As determinants of root growth, the soil matrix water potential and temperature at 15- and 25-cm were measured under both clean cultivation and pine-bark mulch. II was found that during a period of prolonged drought mulching on unfertilized plots increased water retention as expressed in soil matrix potential lower by 150-200 hPa than under clean cultivated soil. On the other hand, with full mineral fertilization, mulching resulted in 15-cm depth in higher soil matrix potential (more water depletion), while ate 25-cm depth a pronounced decrease in potential was found like that on unfertilized plots (more water retained). On both fertilized and unfertilized plots, mulching gave a lower temperature of soil surface layers by 205 degrees. On average, mulching resulted in better growth and higher yield.