• Topics: Agronomy  | Nematode Management in Cotton  | Cotton  |  Wright, David L  |  Rich, Jimmy R  |  Marois, James J 

Alternating Row Patterns in Cotton to Reduce Damage from Reniform Nematodes¹

Reniform nematodes (Rotylenchulus reniformis) have become an increasingly important problem in cotton production in the U.S. and Florida. Management of reniform nematodes is accomplished by crop rotation, nematicides or a combination of these practices since resistant cotton cultivars are not available. For many growers, rotation is not seen as an option due to low alternative commodity prices, and the most effective nematicides are very costly. Thus, other practices need to be developed to provide growers more flexibility to manage reniform nematodes. Our research using strip till planting has centered on several cultural practices that could potentially reduce reniform nematode losses in cotton at little cost to growers. These have included planting cotton between previous crop rows, increasing cotton plant populations and destroying cotton roots soon after harvest. In a preliminary trial, cotton planted strip-till between previous cotton rows showed positive results in a preliminary trial. Cotton lint yield was increased 29% by planting between previous rows as compared to planting into the old cotton row. Further tests, as described herein, have confirmed usefulness of planting between previous cotton rows to reduce losses from reniform nematodes.

Two field trials, one each year were conducted at the North Florida Research and Education Center near Quincy, FL, on a loamy sand soil (80% sand, 8% silt, 12% clay) infested with reniform nematodes. Cotton was grown on this site the year before, and the mowed stubble was left undisturbed over the winter. Two cotton cultivars using Roundup and Bt technology were planted using strip tillage in late June of each year. Rows were 36 inches wide, and the two treatments consisted of planting cotton either directly in-row over the old cotton stubble or planting between the previous cotton rows. The treatments were alternated and replicated six times. Cotton was maintained using standard cultural practices for north Florida. Soil samples for nematode analysis and plant yield were collected from two rows per plot. When soil samples were taken concurrently in the cotton row and between rows, individual cores were taken across from each other to insure comparable sampling areas. Soil was collected for reniform nematode extraction and counted using standard techniques. Seed cotton was manually harvested in early December in the two tests, and subsamples ginned for lint yield.

In Test 1, reniform nematode population densities 28 days after planting were lower in cotton planted between previous rows than that planted over the previous rows (Table 1). As the season progressed, however, reniform nematode population densities in-row in both treatments increased and was roughly equal 76 days after planting. Samples taken after 136 days were collected both in-row and between rows of the two treatments. Reniform nematode population densities were significantly higher in-row in both treatments (mean-1603/100 cm³ soil) compared to row middle populations (mean-544/100 cm³ soil). Cotton yield mirrored early season nematode population density. Yield was significantly higher in cotton planted between previous cotton rows compared to in-row planting.

In Year 2, initial reniform nematode population densities were lower between previous cotton rows than those taken in the previous year's cotton row (Table 2). At both the 81 and 153 day sampling dates, reniform population densities did not differ between the two treatments (Table 3). Additionally, nematode population densities between row middles of both previous-year treatments did not differ from each other but were significantly lower than those found in the planted row of either treatment. Due to the initially lower populations of reniform nematodes in rows middles, however, cotton lint yield was significantly higher than in-row plantings (Table 2).

Present information supports the idea that planting cotton in previous row middles when strip till planting will help avoid a portion of potential yield losses due to reniform nematodes. This is due to population densities of reniform nematodes that are less between rows as compared to in-row populations. However, plant growth, hence root spread, is probably an important factor in the success of this technique. More detailed tests are needed to determine advantages of planting between previous cotton rows over a wide range of initial population densities of reniform nematodes and previous cotton yield. Should these results be applicable under a wide range of conditions, nematicide rates could possibly be reduced, or more likely, row middle plantings could increase nematicide performance. Also, shifting to row middle plantings using strip-till technology does not involve additional grower expense so any yield improvement would be profitable for the cotton farmer.

Concern about compaction has often been the motivating factor in planting back over the old row instead of in previous row middles. This research indicates that where reniform nematodes are a problem, it pays to strip till in row middles. With use of chisels or subsoilers, compaction in row middles should not be a problem, and yields are significantly higher than planting back over last year's row where higher nematode populations exists.

Tables

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean.

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