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.
 
 
 
 
 Significance: 
 
 
 
 Opportunities for improving wheat yields in South Africa need to be explored to address the wheat crisis.
 Sustainable approaches for addressing phosphorus deficiency and acidity of soil under conservation tillage practices need to be sought, especially in the KwaZulu-Natal region.
 
 
 
Highlights
South Africa’s wheat (Triticum aestivum L.) production has declined progressively from 2.5 million tonnes, produced on 974 000 ha in 2002, to approximately 1.7 million tonnes, produced on 500 000 ha in 2013.1 The country is increasingly reliant on imports of wheat to sustain domestic demand
This study contributed to our knowledge pool through quantifying yield gaps and investigating CA practices and soil fertility constraints of irrigated wheat fields in different production areas of South Africa
A yield potential of 13.67 t/ha which was calculated for the cooler central region is comparable to the world record for farm wheat yield of 16.52 t/ha, which was obtained in the United Kingdom.[32]
Summary
South Africa’s wheat (Triticum aestivum L.) production has declined progressively from 2.5 million tonnes, produced on 974 000 ha in 2002, to approximately 1.7 million tonnes, produced on 500 000 ha in 2013.1 The country is increasingly reliant on imports of wheat to sustain domestic demand. The yield potential of irrigation wheat in South Africa is increasing progressively because of improvements in the genetic yield potential of cultivars, pest and disease resistance as well as technological advancements that enable producers to improve crop management.[4] in recent years, researchers and industry agronomists conducting cultivar trials in South Africa have documented potential yields of up to 12 t/ha under controlled field experiments.[5] When these yields are compared with the national average yield of approximately 6 t/ha, it appears that there may be opportunity for improving wheat yield in some production areas of South Africa through refinements of crop and resource management strategies
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