Sustainable sweetpotato farming systems to improve soil health and reduce losses caused by root-knot nematode
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ORIGINAL PAPER
Sustainable sweetpotato farming systems to improve soil health and reduce losses caused by root-knot nematode G. R. Stirling 1
&
A. M. Stirling 1 & M. Prichard 2
Received: 3 April 2020 / Accepted: 20 July 2020 # Australasian Plant Pathology Society Inc. 2020
Abstract Australia produces some of the highest sweetpotato yields in the world but the health of the soil used to produce the crop is declining because it is repeatedly tilled to kill volunteer sweetpotatoes, incorporate cover crop residues and prepare beds for planting. Additional disturbance occurs when the swollen roots are harvested. An on-farm study showed that it is possible to replace this tillage-dominated farming system with an alternative that is not only productive, but is also likely to be sustainable in the long-term. When the soil was amended with organic matter, beds were formed 10 months prior to planting, two cover crops (forage sorghum followed by oats) were grown on the beds, residues from those crops were retained on the soil surface as mulch, and sweetpotato cuttings were planted into the mulched, undisturbed beds using strip tillage, the crop established well and yielded 93 t/ha. The only detrimental effect was that root-knot nematode (Meloidogyne incognita) caused severe damage. In contrast, a trial in the same field showed that when organic amendments were placed in a furrow in the centre of the bed so that the swollen roots were surrounded by the amendment as they developed, nematode control was much better. Sawdust and a mixture of sawdust and chicken litter were the most effective amendments, as they both reduced root-knot nematode populations and the severity of nematode damage, and increased marketable yield by 29%. The wide range of natural enemies found in soil collected from the amended furrow at harvest, and the results of a suppression assay in the laboratory suggested that the soils amended with sawdust and sawdust /chicken litter were biologically suppressive to root-knot nematode. Keywords Biological control . Conservation agriculture . Ipomoea batatas . Meloidogyne . Organic amendments . Sawdust . Chicken litter
Introduction Sweetpotato (Ipomoea batatas) is the world’s sixth most important food crop, with more than 105 million metric tonnes produced globally each year. Although sweetpotato originated in central and south America, Asia now accounts for 86% of the production, with China by far the largest producer. Australia is a relatively small contributor, with total production of around 100,000 t. Nevertheless, its sweetpotato industry has grown remarkably in recent years, with sales increasing by about 20% per annum and yearly production now
* G. R. Stirling [email protected] 1
Biological Crop Protection, 3601 Moggill Road, Moggill, Queensland 4070, Australia
2
Cudgen Road Farms, Cudgen, NSW 2487, Australia
valued at more than $80 million. Most of the crop is grown in subtropical regions, with Bundaberg (southern Queensland) and Cudgen (northern New South Wales) the main centres o
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