Evaluation of mulching in organically grown black current (Ribes nigrum) in terms of its effects on the crop and the environment
1997
Larsson, L. (SLU, Alnarp (Sweden). Inst. foer Traedgaardsvetenskap)
Work in the present project on mulching in organically grown black current has shown that covering the soil with a mulch can strongly influence crop growth and development as well as the environment. In this thesis results from a number of studies dealing with the effects of mulching are summarized and discussed. The main purpose was to increase the knowledge concerning several aspects of mulching, which could then be integrated into an improved use of the method. In accordance with the objective of the work, the thesis includes theoretical discussions on the various effects as well as discussions on the practical applicability of the results. Conditions in the different studies were chosen to be as realistic as possible, and all experiments were done in field. A system of mulching and cover cropping was investigated in organically grown black currant for five years. Different soil parameters were measured in order to study how mulching and cover cropping affect microbial responses. Seven mulches were evaluated in terms of their influence on soil temperature and moisture loss. In addition, the root and shoot growth of young black currant bushes were investigated in terms of their response to mulching with seven different materials. Release of carbon and nitrogen from decomposing green mulches was studied, and ammonia and nitrous oxide emissions from green mulches were measured. The results clearly demonstrate the dynamic nature of growth responses following mulching. Mulching has the potential to increase crop production and can also effectively suppress weeds. However, the results also indicate that it is difficult to achieve improved soil fertility with mulching, at least in the short term. The data obtained imply that there is a considerable risk of losses of N and C to the environment, especially when using N-rich green mulch. It seems to be very difficult to supply adequate nutrients to a black currant crop in the form of green mulch from cover crops growing alongside the rows. Furthermore, the cover crops can complete so severely with the bushes that the fruit yield is reduced. Through improved knowledge on the effects of mulching, it should be possible to develop more effective mulching systems for use in sustainable horticultural systems.
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