Animal manure rhizobacteria co-fertilization suppresses phytonematodes and enhances plant production: evidence from field and greenhouse

The increased demand for agricultural produce can be attained by optimizing the productivity potential and minimizing losses caused by notorious plant-parasitic nematodes (PPNs) in crops. Given the exacerbation of the environmental pollution problem with pesticides, the use of potential biocontrol agents is the most acceptable way of nematode management by the farming community. This study conducted a survey to evaluate three animal [chicken (3.0 g/plant), sheep (5.0 g/plant), and cow (5 g/plant)] manures on soil nematode communities on cucumber under greenhouse conditions and inoculated with plant growth-promoting rhizobacteria (PGPR) and their infectivity and the plant growth and crop production of tomato under field conditions compared to oxamyl (0.3 mL/plant). The survey concluded to spread 10 PPN genera, free-living nematodes (FLNs; Genus: Rhabditis), and predacious nematodes (PNs; Order: Mononchida). The root-knot nematode Meloidogyne spp. occupied the highest population density (PD; 60.41%), followed by the lesion nematode Pratylenchus spp. (38.72%) and then the spiral nematodes Helicotylenchus spp. (9.89%) and Tylenchus spp. (9.54%). The frequency of occurrence of phytonematode genera illustrated that Meloidogyne (35.41%), Pratylenchus (17.18%), Tylenchorhynchus (15.62%), and Tylenchus (11.45%) were the most frequent genera of phytonematodes. The higher prominence value was recorded with Meloidogyne, followed by Pratylenchus and Tylenchus. Under greenhouse conditions, an increase in plant growth parameters was recorded in cucumber plants that received the recommended rate of chicken, cow, and sheep manures, with no significant differences between chicken manure and oxamyl in root length and stem diameter. However, chicken manure treatment surpassed oxamyl in fresh root weight. Animal manure effects were extended for a long period in protective cucumber plants compared to control treatment by recording the lowest PD of Helicotylenchus spp., Tylenchorhynchus spp., and Pratylenchus spp. and the maximum decrease in galling and reproduction of Meloidogyne incognita. In the field experiment, test manures and PGPR combinations achieved maximum enhancement in tomato yield/plant compared to animal manures alone. The minimized numbers of M. incognita population coincided with the sustainable numbers of FLNs and PNs. Thus, the application of animal manures mixed with PGPR is a potential alternative to pesticides for the biological control of nematodes.

Automated summary

The study found that the combination of animal manures and plant growth-promoting rhizobacteria can effectively reduce the harm of root-knot nematodes in tomato production, and also have a significant impact on the growth of cucumber.