The Impact of Ground Cover Management on Soil Nitrogen Levels, Parameters of Vegetative Crop Development, Yield and Fruit Quality of Strawberries

The aim of this research was to elucidate the impact of various mulches on N availability in the soil, the plant development, as well as the yield and quality of strawberries (Fragaria x ananassa Duch.). Field experiments were established in 1995 with the strawberry cv. 'Petrina' in the midlands of Switzerland. The following interrow soil covers were compared at a moderate rate of nitrogen fertilization (3 × 20 kg N ha-1): bare ground (control), black and white water-permeable Mypex films, straw added after planting and a living mulch of a non-winterhardy white clover (Trifolium repens L.). In the latter two systems, the rows were covered by bands of water-permeable black polyethylene plastic film (30 cm wide). The content of mineral nitrogen (Nmin) in the soil was measured in and between the rows (25 cm apart) and in different soil layers throughout crop development. Parameters of vegetative crop development, such as the formation of runners after planting and total leaf area per plant, were also measured. Moreover, concentrations of total N and nitrate in the leaf blades, fruit yield, fruit size, and parameters of fruit quality of cv. 'Petrina', e.g. soluble solids, titratable fruit acid, and the firmness and shelf life of the fruits were assessed. Black and white Mypex films did not have consistent effects on Nmin values in the soil. With continuous decreases in Nmin, winter straw mulch in particular reduced the risk of nitrogen leaching in the interrow area during winter. The white clover mulch treatment clearly decreased Nmin only in the year of planting. The white clover mulch treatment also resulted in a decrease in the number of runners. Ground cover management did not have a significant effect on leaf area. Straw and living clover mulches hindered flower formation, possibly as a result of shading. Moreover, the white clover mulch significantly decreased the fruit yield. Compared to the black Mypex film, the white film reduced the formation of runners, while the number of flowers increased slightly. The colour of the plastic mulches did not have a significant effect on the fruit yield. The size of the fruit was affected to a slight extent by the ground cover treatments. The content of titratable fruit acid increased in the straw and living clover mulch treatment. The fruits were, on average, most firm in the control treatment with bare ground. Based on these studies, we recommend using black and white plastic mulches for strawberry production on sa