Effects of Cropping Frequency on Potato Production

Abstract

High cropping frequency of potatoes, particularly continuous cultivation, can lead to physical and economical yield losses because the population densities of soil-borne pathogenic organisms are enhanced. Such organisms diminish crop growth and often necessitate costly control measures.

Analysis of data from the literature showed that potatoes in continuous cropping yielded initially just as well as potatoes in a rotation, but sooner (after two to three seasons) or later (after about five to seven seasons) yield reductions usually appeared with continuous cropping. Studies in which a range of cropping frequencies were studied, e.g comparisons of 2, 3, 4, 5 or 6 course rotations, showed systematically lower yields as the cropping frequency increased, particularly when the cropping frequency was higher than 33 to 50 per cent. The magnitudes of the losses were usually in the order of 5 to 25 per cent. Much higher losses were incurred when the potato cyst nematode was the pathogen affecting plant growth.

Potato cyst nematodes and Verticillium spp. were most often mentioned as the pathogens that were responsible for yield losses, but also other organisms can be involved. Differences in parameters in the domain of soil physics were rarely examined in rotation studies.

Cultural practices, such as the supply of mineral fertilizer and water or the addition of organic matter did not appear to nullify or alleviate the effects of cropping frequency on yield.

There were no specific effects of the cropping frequency on the quality of the tubers, except those due to organisms that infect or malform the skin (e.g. Rhizoctonia solani, Meloidogyne chitwoodi, Streptomyces spp).

In a rotation the preceding crop can influence potato yield. Mainly because its cultivation can stimulate the build up of common pathogens and can influence the relative deficiency of nutrients when these are in short supply.

In order to maintain profitable specialized production of potatoes, more quantitative analyses need to be made of the factors that cause yield reductions in short rotations and of their interactions. Improved seed health, improved hygienic measures on the farms, the incorporation of genes for resistance against the major pathogens, and strategies for use of cultivars with different resistance genes in practice are domains where research efforts should be continued. A specific task is the development of an expert system that contains the available information on the relations between crops and pests and diseases.