Potato (Solanum spp.) in the hot tropics III. Influence of mulch on weed growth, crop development, and yield in contrasting environments

Abstract

Abstract Eighteen experiments at three hot tropical sites (5–12 °S, 180–800 m) within Peru were run with various mulches over a 4-year period. Mulch, although suppressing weed growth, favoured both crop emergence and the stand of tuber-bearing plants at final harvest. Canopy development, crop cover and light interception over the season were almost invariably improved by mulch. Tuber initiation, when measured, was earlier and tuber growth rates greater for mulched plants. Tuber yield was consistently increased by mulch in all but two experiments, averaging 25% over all experiments. Yield improvements due to mulch were less evident at the hottest site, where high soil temperature (> 25 °C) during the night at tuber depth, high natural reflectivity of the soil (0.18), a large sand fraction in the soil, and cloudy days and nights, were considered responsible for inconsistent benefits of mulch on tuber yield. At another site, where mulch was also tested during the rainy season, yield was on average improved by mulch in a proportion similar to that during the dry season at the same site. Mulch was particularly beneficial in improving all measured aspects of crop growth and yield when combined with agronomic treatments that, on their own, predisposed plants to greater heat stress. For example, mulch was more effective in ridge than on the flat plantings, at planting depth less than 7 cm, at lower plant populations and for small-canopied determinate clones. Environmental and biological criteria for the successful use of mulch for potato cultivation in hot climates are discussed.