Impact of Agricultural Land Use on Nematode Diversity and Soil Quality in Dalmada, South Africa

Abstract

During a survey on soil nematode diversity, the soil samples were collected from Field-1 (3-months-not-used land), Field-2 (5-years-not-disturbed land), Field-3 (the rhizosphere of tomatoes), and Field-4 (natural land, not disturbed for 50 years), in Dalmada, Limpopo Province, South Africa. A total of 25 nematode genera were found to be associated with the surveyed plant species. The result showed Acrobeloides, Aphelenchus, Aporcella, Ditylenchus, Mesorhabditis, Pratylenchus, and Rotylenchus with a 100% frequency of occurrence. Meloidogyne was detected only in association with Field-3, with a low frequency of occurrence (25%). The study of the relationship between nematodes with physicochemical properties in the soil using Pearson correlation revealed that phosphate of the soil had a positive correlation (r = 0.977) with Bitylenchus and Pseudacrobeles species. In contrast, pH strongly correlated with Nanidorus (r = 0.928), Trypilina (r = 0.925), Xiphinema (r = 0.925), and Zeldia (r = 0.860). The principal component analysis placed Field-4 and Field-3 in two groups, indicating the biodiversity dynamics among the two locations. Soil texture showed that clay was correlated with Rotylenchulus. In contrast, soil texture had no effect on Meloidogyne. The Shannon index was the lowest (1.7) for Field-1 in Dalmada compared to the other Fields, indicating lower nematode diversity. The structure index showed that Field-2 was disturbed with a low C:N ratio. In contrast, Field-3 and Field-4 had suppressive soil but matured and fertile. The network analysis showed that Panagrolaimus was only found in Field-4 and was the most engaging genus describing soil quality in the soil system in Dalmada. In conclusion, Field-2 showed a high diversity of free-living nematodes than the disturbed land of tomatoes. Additionally, plant-parasitic nematodes numbered more in the rhizosphere of tomatoes. The results suggest that the soil nematodes, especially free-living bacterivores, may mediate the effects of ecosystem disturbance on soil health.

Association of Plant-Parasitic Nematodes and Soil Physicochemical Properties in Tomatoes in Turfloop, Limpopo Province, South Africa

“…Ammonium (NH 4 + ) was shown to have a positive (Rotylenchus) or negative (Rotylenchulus) correlation with plant-parasitic nematodes [5]. The same result was obtained in the present study with a positive correlation between NH 4 + and Rotylenchus.…”

“…Several studies have delved deep into the influence of the chemical properties of soils affecting plant vigor and consequently affecting the distribution and population density of nematodes. These studies have shown that chemical composition significantly regulates nematode population dynamics by affecting plant health and productivity [5,21].…”

“…The result of the present study showed that there is no correlation between Meloidogyne and soil textures. Another survey of tomatoes in South Africa showed that soil textures, including clay, silt, and sand, had no effect on Meloidogyne [5]. Moreover, Rotylenchulus showed a negative correlation with boron (B).…”

“…As a result, PPNs represent a significant threat to the agricultural industry, and their control is of utmost importance for sustainable agriculture [2]. The impact of the plant-parasitic nematodes has been recently studied in tomato production in Ethiopia [3], Kenya [4], and South Africa [5]. Jones et al [6] identified Meloidogyne spp.…”

“…These nematodes, also known as root-knot nematodes, infect plant roots, causing the formation of knots that impede water and nutrient uptake. In South Africa, root-knot nematodes, particularly M. incognita and M. javanica, are a significant threat to tomato crops [5]. These nematodes can cause stunted growth, reduced fruit production, and even plant death, leading to significant economic losses for farmers.…”