- Agronomic: peanuts
- Crop Production: cover crops
The plant parasitic nematodes from the genus Meloidogyne spp. (a.k.a. Root-knot nematodes, RKN) are one of the leading causes of losses in production of peanut (Arachis hypogaea) in the Southeastern U.S. One of the most sustainable measures that a farmer can implement is to use the resistant peanut cultivars. However, farmers tend to avoid the RKN-resistant peanut cultivar because they usually have low yield and/or kernel quality when compared to elite (RNK susceptible) cultivars. To avoid decreasing the peanut quality in production system, the alternative sustainable practice is the use of crop rotation. However, crop rotation is not a viable approach in central Florida, where peanut is planted every year. In this region, the last and least sustainable measure is used: annual application of nematicides. While the use of cover crops is prevailing in other parts of the country and information was widely available to crop growers, similar situations did not exist in the state of Florida. This project evaluated the nematode suppression capacity of six winter cover crops that are resistant to RKN and their subsequent impacts on peanut production. Two-season field experiments with six winter cover crops (plus control) followed by peanut growth were established in Plant Science and Research Education Center near Gainesville. The yield, height and percentage coverage of cover crop species were measured as well as the peanut yield. The RKN population was quantified before the establishment of cover crops and monitored until the harvest of peanut on the second year. The yield of grasses cover crops was significantly higher than other species regarding dry matter yield and this phenomenon was consistent across two years. Grasses showed lower nematode population than legumes during the cover crop season. However, when nematodes were present in the peanut season (only second season) this pattern changed and legumes showed lower nematode count than grasses treatments. While nematodes were present in most of the study period, appear that their number was not enough to create significant damage in the peanut plant and kernel health.
Root-knot nematode (RKN) species are the predominant parasite of Florida peanut production, causing significant damage both to peanut yield and quality (Minton and Baujard 1990, McSorley et al. 1992, Dickson and De Waele 2005). The most sustainable farming practice alternative is to use the RKN-resistant peanut cultivars, such Tifguard or COAN. However, even though these cultivars have high resistance to RKN, their peanut yield is lower than top-yielding cultivars, such as the most popular peanut cultivar Georgia-06G. Crop rotation with cotton is another sustainable alternative used to decrease and avoid crop loss by nematode damage. However, due to the climatic conditions, this is not an alternative for central Florida. Thus the use of chemical control (nematicides) is the only option currently available to farmers of central Florida when susceptible peanut varieties are used. However, the application of nematicides increases production cost, breaks the ecological balance in the soil environment, and eliminates biological control agents, ultimately leading to reducing the sustainability of the agricultural system (Bridge 1996).
Cover crops are generally used as agricultural cultural practices to improve the soil fertility, structure, and suppress weeds, nematodes, and other plant pathogens (Janzen et al. 1992). Additionally, winter cover crops species, including Triticum spp. (wheat), Trifolium repens L. (white clover), Trifolium pretense L. (red clover), Vicia sativa L. (common vetch), Vicia villosa (hairy vetch), Secale cereale L. (rye), and Tricoselace (triticale), may bring benefits beyond the nematode suppression. All of these cover crops can additionally be used as cash crops for grain or forage. The use of clovers can also benefit soil nutrition by fixation of nitrogen. The red clover cultivar ‘Southern Belle’ was selected for high resistance to M. arenaria race 1, M. incognita race 3, and M. javanica. The white clover cultivar ‘Ocoee’ was also selected for resistance to M. arenaria, M. incognita, and M. javanica. These two clover cultivars have shown low gall and egg mass number and interference with nematode developmental process and, therefore have been recommended for crop rotation (Call et al. 1996, Quesenberry et al. 2005). Both the rye, ‘Florida 401’, and triticale, ‘Trical 342’, have been shown to have low egg mass and to affect the reproduction of M. arenaria race 1, indicating they could be the potential superior candidates to suppress the nematode population (Ibrahim et al. 1993). The wheat cultivar ‘SS8641’ is an ideal cover crop due to its high resistance to leaf rust and stripe rust and it may possess the ability to suppress the nematode population in the field.
By using RKN-resistant cover crops, it is expected that nematodes are able to identify and infest the cover crop plants, but not being able to develop or reproduce in them, thus reduction of the population of RKN could be achieved. For example, Quesenberry et al (2014) observed that the RKN-resistant red clover ‘Southern Belle’ reduced the fecundity of egg masses and thus suppressed the nematode development. If reproduction of nematode is suppressed, then its overall population ought to decrease. Additionally, RKNs are endoparasitic pests which means they become sedentary after they migrate to the target vascular bundle (Bird et al. 2009). Therefore, unlike mobile cyst nematodes, after harvest of the cover crops, the nematodes in their roots will be trapped in the immobile stage unable to migrate to infest the subsequent crop. By identifying the cover crops that can be used to decrease the population of RKN in the field, it is expected that the RKN susceptible peanut cultivars with high yield and quality can continue to be used by farmers, reducing the quantity of application of nematicides and their negative impact on the environment. While cover crops have been extensively studied in the northern part of the US, limited information is available in term of its usage in Florida. It has been promoted that more studies are needed to encourage farmers to adopt this sustainable alternative.
The goal of this study is to identify the cover crop species/cultivar that can reduce the RKN-nematode population in a peanut production systems of central Florida and thus increase the yield of peanut. Specifically, evaluate the suppression of root-knot nematode (RKN) population from six winter cover crop cultivars resistant to RKN and measure the their effects on subsequent peanut yield in a peanut production rotation system.