RENOVATION OF EXTRACTED HIGH BOGS IN LATVIA: MINERAL NUTRITION AND ECOLOGICAL ASPECTS OF AMERICAN CRANBERRY CULTIVATION

Abstract

Latvia is a country with abundant peat resources and intensive peat production. Therefore restoration of more than 17,000 ha abandoned and excavated high bogs are an important issue. Scientific researches are necessary to choose the best way for renovation of peatlands after peat cutting. Along with sufficient freshwater supply this specific nutrient-poor and acid growing environment provides the possibilities for commercial cultivation of American cranberry (Vaccinium macrocarpon) which was successfully started during last 15 years. Today with more than 100 ha of plantings Latvia is fourth major cranberries producing country. In contrast with North America little is known regarding the fertilizing systems of cranberries planted on bare sphagnum peat. Being a native wetland plant, cranberries are nutrients low requiring culture; however, balanced mineral nutrition is vitally essential in producing high and qualitative yield. On the other hand, excessive or inadequate fertilization is potentially detrimental to the environmentally sensitive cranberry growing medium. Investigations were done to find out the actual status and main tendencies in mineral nutrition of American cranberries in Latvia during 2001–2009. Peat samples from 60 different cranberry producing sites established on extracted high bogs were collected over two periods: 2001–2004 and 2005–2009. Additional 20 samples from cutover and natural bogs were analyzed for background level to assess the changes in peat nutrient content during cranberry cultivation. Soil (peat) testing was used to evaluate the cranberry supply with nutrients (N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, Mo, B). Peat analysis revealed serious imbalance in cranberry providing with essential mineral elements. Deficiency of N P, S, Fe, Mn, Zn, Cu, Mo, and B were stated in the majority of samples. Positive tendencies in nutrient status of cranberry peat were found from 2001-2004 to 2005-2009. Mean concentrations increased for P, K, Ca, Mg, Fe, Mn, Cu, B, and become more corresponding to soil standards. Our results revealed significantly higher mean concentrations of P, K, Ca, Mg, S, Fe, and Mn in cultivated cranberry peat to compare with background level, although only P, Ca and Mg contents exceeded maximal levels of these nutrients stated in cutover peatlands. Lack of seriously increased nutrient concentrations in peat samples (only 3% of indices in high levels) indicated that cranberry fertilization practices in Latvia are likely not detrimental to the environment. The present investigation forms the basis for development of on scientific knowledge based cranberry fertilization guidelines in Latvia.