The combination of composted animal manure and plant growth-promoting rhizobacteria is a sustainable biofertilizer and bionematicide for grapevine (Vitis vinifera L.) cultivars

Root-knot nematodes (RKN) cause extensive damage to grapevine cultivars. RKN-resistant grapevine rootstocks remain vulnerable to biotic and abiotic stresses. This study aimed to determine the influence of composted animal manures (CAMs) [chicken manure (CM), cow manure (CowM), and sheep manure (SM)] with or without plant growth-promoting rhizobacteria (PGPR) on the population of Meloidogyne incognita, free-living nematodes (FLNs) and predaceous nematodes (PNs) residing in the soils of vineyard cultivars (Flame, Superior and Prime). The nematodes were isolated from grapevine roots and rhizosphere soils, then the absolute frequency of occurrence (FO), relative FO, prominence value (PV), and population density (PD) were assessed. The impact of CAMs and PGPR on the growth parameters, fruit output, and quality of three grapevine varieties was subsequently evaluated. Eight treatments included a control without CAMs or PGPR amendments, the CAMs alone, or CAM treatments combined with PGPR. The results showed that FLNs and PNs were more abundant in Prime than Flame or Superior cultivars when poor sandy loam soils were supplied with CAMs. Among all tested manures, CM was the best treatment as a nematicide. This was evident from the decreased numbers of M. incognita and increased numbers of FLNs and PNs in grapevine fields. Compared to the soil-applied oxamyl (a systemic nematicide), which was efficiently suppressive on M. incognita for two months, CM significantly (P < 0.05) decreased PD of the phytonematodes for five months, improved soil structure and enhanced the soil biological activities. There were significant (P < 0.05) increases in the number of leaves/vines by 79.9, 78.8, and 73.1%; and total fruit weight/vine by 76.9, 75.0, and 73.0% in Flame, Superior, and Prime varieties, respectively, compared to untreated vines. Regardless of the cultivar, soils amended with CM + PGPR achieved the lowest number of M. incognita among all other treatments, followed by SM + PGPR and CowM + PGPR. It was concluded that CAMs amendment, mainly CM, along with PGPR in poor sandy soils of temperate areas, is considered a sustainable approach for reducing parasitic nematodes and improving agricultural management.