TILLAGE AND WATER STRESS EFFECTS ON FRUITING PATTERNS OF COTTON

P.E. Hoskinson and D.D. Howard

ABSTRACT

Tillage and water stress effects on fruiting patterns of cotton were evaluated in studies at Jackson and Milan, Tennessee in 1991. The experiments consisted of cotton which was conventionally-tilled and no-tilled into old cotton stubble. The Jackson experiment was irrigated three times and received 1.28 inches of water July 18, 1.0 inches August 6, and 0.8 inches August 19. The Milan experiment did not receive supplemental irrigation. One "average" plant per plot was selected and mapped throughout the season at Milan. Two were selected and mapped at Jackson. Data reported are averages for 48 plants grown in no-tillage and conventional-tillage at Jackson and 35 plants grown in no-tillage and conventional-tillage at Milan. Harvestable bolls were mapped and hand-picked for subsequent evaluation.

No-tilled plants were slightly taller throughout the season at Milan, but the reverse was true at Jackson. Total number of main stem nodes were virtually identical throughout the season for both tillage systems at both locations. Lint yields from conventionally-tilled plots were 13.7% higher at Jackson and 7.6% higher at Milan than yields obtained from no-tilled plots. Conventionally-tilled plots were 11% earlier at Jackson, but were not different at Milan.

Sixty percent of seed cotton yield was produced at fruiting position 1 in no-tillage and 59% in conventional-tillage at Milan. Sites 1 and 2 produced almost 83% of seed cotton yield from both tillage systems. Only 4% was produced at sites 3 or more while 13% was produced by monopodial branches at Milan. We obtained 11.2 bolls per plant from conventionally-tilled plots and 10.5 bolls from no-tilled plots. Bolls from conventionally-tilled plots were 0.46 grams per boll larger. However, gin turnout of no-tilled plots was 1.1% higher than gin turnout of plants that had been conventionally-tilled.

Only 66% of the seed cotton yield from no-tilled plots at Jackson was produced at sites 1 and 2 and only 64% was produced by conventionally-tilled plots. Sites 3 or more accounted for approximately 5% of the yield of both tillage systems. An unusually large 29% of seed cotton was located on monopodial branches of cotton plants no-tilled into cotton stubble and 31% on plants conventionally-tilled. Plants on conventionally-tilled plots, held 13.8 bolls/plant while plants in no-tilled plots averaged 17.4 bolls at Jackson. Boll size of no-tilled plants was 4.45 gms/boll compared with 5.21 gms/boll on plants conventionally-tilled. Gin turnout of cotton produced by conventional-tillage was 2% higher than that produced by no-tillage. An unusually low plant population of 1.52 plants/ft. row, no-till and 2.07 conventional-tillage may have influenced fruiting patterns of the experiment at Jackson.

Sympodia arising from nodes 4 through 12 accounted for 82.6% of the Milan yield averaged across both tillage systems, but only 56.5% of the yield at Jackson. When seed cotton yields obtained from monopodial branches were added to all plots at both locations, it becomes clear that increased yield due to irrigation at Jackson was largely produced on sympodia above node 12 and on monopodial branches. Irrigation encouraged boll retention later in the season as shown by 37.6% boll retention on monopodial branches of plants grown at Jackson compared with 19.3% retention by plants of both tillage systems at Milan. Overall, boll set at Milan averaged 30.8% for plants grown no-tillage and 34.6% for conventionally-tilled plants. Comparable data at Jackson were 42.2% harvested bolls for plants grown in no-tillage culture and 38.7% for conventionally-tilled plants.

Lint yield averaged 1190 pounds/acre for no-tilled plots and 1353 pounds for conventionally-tilled at Jackson; no-tillage plots at Milan yielded 1170 pounds and conventionally-tilled plots at Milan averaged 1259 pounds lint/acre.





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Document last modified July 8, 2004