Cotton Genotype Response to Soil Conditions Associated with the Use of Cover Crops

P.J. Bauer, J.M. Bradow, and C.C Green


 
ABSTRACT

Cotton (Gossypium hirsutum L.) plant populations are often reduced when planting occurs following a winter legume in both conventional and conservation tillage systems. Reasons for reduced cotton stands have not been fully explained, but ammonia toxicity, increases in soil pathogens, and toxicity from volatile organic compounds have been implicated. Experiments were conducted to determine if genetic variability exists for soil conditions associated with the use of legume cover crops.

Thirty genotypes were evaluated in a laboratory assay in which seeds were germinated in the presence of decomposing crimson clover (Trifolium incarnatum L.). Three genotypes, 'Coker 315', 'PD 3', and the germplasm line 'PD 5246' were selected for field studies in 1991 and 1992 based on root length results from that assay. Ranking of these three genotypes, in order of sensitivity to the clover residues, was Coker 315 > PD 3 > PD 5246.

In the two year field study, these three genotypes were planted 7 days after incorporating a crimson clover cover crop or winter weeds (winter fallow). Experimental design was randomized complete block in splitplot arrangement with four replicates. Main plots were winter covers and subplots were genotypes. Cotton plant populations and yield were measured. In 1991, both Coker 315 and PD 3 had significantly reduced stands in the clover winter cover treatment compared to the winter fallow, but PD 5246 was not significantly affected. Yields in that year were not influenced by cover treatment. In 1992, all three genotypes had reduced stands in the clover plots, but PD 5246 was the only genotype that had similar yields in both cover treatments. For Coker 315 and PD 3, yield was significantly reduced in the clover winter cover treatment. Thus, it appears that genetic diversity exists for the soil conditions associated with the use of cover crops, and that PD 5246 is superior in that production system compared to the other two genotypes.

Experiments have been conducted to identify the specific trait(s) which make PD 5246 superior in this system. No difference between these genotypes were found in a laboratory assay developed to test for ammonia tolerance. However, PD 5246 was less susceptible than the other two genotypes to several of the known organic volatiles that are emitted from decomposing crimson clover. These results indicate that cultivar improvement for soil conditions associated with the use of cover crops may be achieved through developing cottons that are more tolerant of these organic volatiles.



Reprinted from 1993 Proceedings Beltwide Cotton Conferences pg. 609
©National Cotton Council, Memphis TN

[Main TOC] | [TOC] | [TOC by Section] | [Search] | [Help]
Previous Page [Previous] [Next] Next Page
 
Document last modified Sunday, Dec 6 1998