Short-term crop rotation interactive effects on soil microbial communities and potato yield under field conditions

The inclusion of plant-parasitic nematode (Meloidogyne species) non-host crops in potato (Solanum tuberosum L.) -based cropping systems can sustainably manage the pest and reduce the application of greenhouse gas-emitting agro-chemicals. Nevertheless, there exists a research gap on how these cropping systems interact with soil microbiome.

A 2-year field study was conducted at the University of Limpopo and the Agricultural Research Council to investigate the effects of potato monoculture, Cucumis africanus-potato, sorghum-potato and potato (Velum)-potato cropping sequences on soil health and tuber yield. The treatment crops, namely, sweet stem sorghum (Sorghum bicolor) cv. 'Ndendane-X1', C. africanus, potato cv. 'Mondial G3' and potato cv. 'Mondial G3'-velum (control), were assigned to 4 m² subplots in Sequence 1, in a randomized complete block design, with six replicates. The successor potato crop was planted in Sequence 2. Crop arrangement in Sequences 3 and 4 was as in Sequences 1 and 2, respectively. Soil organic carbon content, enzyme activity, nematode and bacterial functional diversity data were collected from Sequences 1 to 4. Final potato tuber yield was recorded in Sequence 4.

Based on the results, nematode indices revealed disturbed agroecosystems dominated with bacterial decomposition pathways, which is a common occurrence in intensively managed soils. High soil organic carbon content, microbial diversity and enzyme activity were observed in sorghum-potato and C. africanus-potato compared to potato monoculture (with or without velum), at both locations. In addition, sorghum-potato improved soil structure over time based on the nematode faunal results, thereby depicting its ability to promote soil health compared to other cropping systems. Tuber yield mass significantly varied (p ≤ 0.05) among cropping sequences at both locations with potato (Velum)-potato and C. africanus-potato sequences recording higher yields than potato monoculture or sorghum-potato.

Crop diversification increased soil organic carbon content, microbial diversity and enzyme activity. Overall, sorghum-potato effectively improved soil health and soil structure over time, better than the other cropping systems.