Yield and dry matter allocation in soilless strawberry with sheep manure compost

Soilless production of strawberry decreases the dependence for soil pesticides while increasing crop yields. Compost is a suitable substrate for sustainable horticultural production; however, due to the diverse characteristics of the final product in composting, careful analysis of its effect on soilless culture must be done. Yield and growth of strawberry cultivars ‘Festival’, ‘Jacona’ and ‘Zamorana’ grown on either peat-perlite (1:1) or compost-peat-perlite (2:1:1) were compared using a split-plot experimental design with the substrate as main plot. Compost was made of fresh sheep manure. Cold-treated plants (1°C/98 days) were planted inside a glasshouse on March 1, 2013. Throughout the 400 days of evaluation (six destructive samplings) root yielded more dry matter in plants grown without compost than those grown with compost (p≤0.02) for a root-shoot ratio of 0.85 vs. 0.56 (beginning) to 0.27 vs. 0.23 (ending) from plants in substrate without and with compost respectively. Comparing root-shoot ratios among cultivars, ‘Zamorana’ achieved the lower (0.58) and ‘Festival’ the higher values (0.79) at the beginning but similar values at the end of the experiment were recorded (0.26 vs. 0.27, respectively). Monthly fruit yield was not consistently affected neither by substrate nor by cultivar. Total yield of 355.5 and 330.7 g of fresh fruit weight were obtained in plants cultivated without and with compost respectively (p=0.117) and ‘Zamorana’ yielded higher than ‘Festival’ (378.1 vs. 317.4 g plant^‑1 respectively; p=0.006). In general, dry matter allocation to root and leaves decreased during fruiting and photosynthesis decreased at onset of fruiting but then leveled up to similar values than those at the beginning, thus being interpreted as dry matter of these organs supporting fruiting more than current photosynthesis. As a conclusion, compost in the growing substrate could decrease strawberry root growth without affecting fruit yield as dry matter of root and leaves might support fruiting.