Sustainable sweetpotato farming systems to improve soil health and reduce losses caused by root-knot nematode

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.

Integrated Nematode Management

“…The results obtained at harvest were also encouraging, as the marketable yield in both the sawdust and sawdust/chicken litter treatments was 93 t/ha. When compared to the non-amended control, both treatments increased marketable yield by 29% and reduced final populations of root-knot nematode by 43% and 39%, respectively (Stirling et al, 2020).…”

Sustainable sweetpotato production in the United States: Current status, challenges, and opportunities

“…Root knot‐nematodes (RKNs) affect a wide range of vegetables, row crops, and perennial plants (Nyczepir & Thomas, 2009). Even low levels of RKNs in the soil can reduce crop yield and the quality of roots (Karssen et al., 2013), and RKNs are found in nearly all areas where sweetpotatoes are grown (Clark et al., 2013; Stirling et al., 2020). Aboveground symptoms of RKN infection are nonspecific: chlorosis, necrosis, plant stunting, or wilting as the plant is under duress.…”

A High-Throughput Sampling Method for Detection ofMeloidogyne enterolobiiand Other Root-Knot Nematodes in Sweetpotato Storage Roots

“…These pests migrate into the roots of a host plant and establish elaborate feeding sites within the root (Chitwood 1949). After establishing its feeding site, the nematode will remain inside the root for the rest of its life cycle (Krusberg L. R. and Nielsen 1958;Stirling et al 2020). The juveniles develop into mature females which can each produce hundreds of eggs (Karssen et al 2013).…”