Effect of cropping system and peat amendment on strawberry growth and yield

Comparative studies have usually shown higher yields in conventional cropping systems (CCS) than in organic cropping systems (OCS). By utilizing a long-term field experiment on silt soil with 18 years of cropping history (1982–1999), including three OCSs and one CCS, we studied if this is true also for strawberry. The strawberry experiment was conducted in 2000–2002. The experiment had one CCS (A) and three OCSs (B,C,D). The impact of pre-planting peat amendment was also studied. The degree of overwintering, fruit yields, yield components and some soil nutrients were determined. Total and marketable fruit yields were estimated using a peduncle analysis based on weights of fruits of different orders in the peduncle, numbers of healthy and injured fruits in the peduncle and the number of peduncles per plant. The shoot growth, total and marketable fruit yields, as well as all yield components estimated were significantly higher in the OCS rotation D than in the CCS rotation A. The peat amendment, but not the cropping system, decreased the percentage of strawberry plants suffering from or killed by winter damage. However, peat amendment did not affect yield. The cropping system had no impact on soil pH, or the amount of extractable calcium, magnesium and nitrate. Extractable phosphorus and potassium were higher and soil organic carbon (Corg) slightly higher in the OCS than in the CCS. The peat amendment increased Corg by 2%. The amounts of extractable nutrients in soil were not a limiting factor for strawberry growth and yield as they were of sufficient levels both in CCS and OCS. It remains unclear whether the higher yield in the OCS was due to a long-term cropping history or to a short-term effect of composted manure, or to a combination of these two. The importance of soil organic management in strawberry production is emphasized.