Soil fertility constraints and yield gaps of irrigation wheat in South Africa

Abstract

South Africa currently faces a wheat (Triticum aestivum L.) crisis as production has declined significantly over the past few years. The objective of this study was to explore opportunities for improving yields in intensive irrigated wheat production systems of South Africa through analyses of yield gaps, soil fertility constraints and conservation agriculture practices. The study was conducted in the major irrigation wheat production areas across four geographical regions: KwaZulu-Natal, eastern Highveld, warmer northern and cooler central. Actual yield (Ya) based on long-term yield data ranged from 5.99±0.15 t/ha to 8.32±0.10 t/ha across different geographical regions. The yield potential (Yp) ranged from 7.57 t/ha to 11.45 t/ha. Yield gaps (Yp–Ya) were in the range of 1.58–3.13 t/ha. Yields could be increased by 26–38% through closing yield gaps. On 88.37% and 13.89% of the fields in the KwaZulu-Natal and warmer northern regions, respectively, there was strong evidence of the practise of conservation agriculture, but none in the other regions. On 42.31% of irrigated wheat fields, soil organic carbon was below 1% at a soil depth of 0–20 cm. Fields in which conservation tillage was practised had double the soil organic carbon of conventionally tilled fields (2.15±0.10% versus 1.02±0.05%), but greater acidity and phosphorus deficiency problems. Sustainable approaches for addressing phosphorus deficiency and acidity under conservation tillage practices need to be sought, especially in the KwaZulu-Natal region.

The benefits of conservation agriculture on soil organic carbon and yield in southern Africa are site-specific

“…In a review, Cheesman et al (2016) drew similar conclusions for southern Africa. However, other similar site-specific studies found that RT could effectively increase SOM (Kotze and Du Preez, 2007;Govaerts et al, 2009;Sosibo et al, 2017). Our study confirms this but concurrently points to the fact that this depends strongly on the particular soil (and weather) conditions.…”

Aligning Conservation Agriculture among various disciplines in South Africa

“…For the same production systems, Crookes et al (2017) demonstrated that a more diverse crop rotation system resulted in higher profitability, particularly for cropping systems integrated with livestock. In addition, enhanced soil organic C sequestration as a result of no-tillage has been widely reported for South African crop production systems and is assumed to be generally beneficial (Agenbag and Stander 1988;Kotze and du Preez 2007;Sosibo et al 2017;Swanepoel et al 2018). However, there are also examples of systems where no-tillage did not result in increased soil organic C contents (Sithole and Magwaza 2019).…”

Spatio-seasonal variations in the faecal bacterial community of Zulu sheep grazing in communally managed rangeland

“…This difference between the newer and older cultivars is usually not more than ZAR500 per 50-kg bag. It should also be noted that seed costs typically contribute less than 5% of establishment costs for a commercial irrigation wheat crop in South Africa, 4 hence lower seed price is seldom the major reason for choosing a lower yielding cultivar over a higher yielding one.…”

“…3 A preliminary study on yield gaps of irrigation wheat in South Africa showed that while yield averages ranged from 6.0 t/ha to 8.3 t/ha, the yield potential ranged from 7.6 t/ha to 11.5 t/ha. 4 Conclusions were that irrigation wheat yields could be increased by 26-38% in the major production areas of South Africa. However, information presented in the yield gap studies was not conclusive regarding solutions for closing the yield gaps.…”