Weed Management and Plant Growth Regulator Comparisons in Drip Irrigated Cotton

(Field 6H)
Wayne Keeling, John Everitt and Leanna Lyon

Fig. 1. Cotton harvest of weed management, growth regulator study irrigated by SDI at Helms Farm, 2002.Objective: The objectives were to:

1) Evaluate the effectiveness of two herbicide scenarios on weed control and lint yield.

2) Evaluate a new plant growth regulator against mepiquat chloride.

Methodology: Paymaster 2326 BG/RR and Fibermax 989 BG/RR were planted on May 6, 2002 in three replications (16 rows x 250’ long) in a subsurface drip irrigated field. The seasonal herbicide scenarios were as follows: 1) Prowl (pre-plant incorporation) followed by a broadcast application of Roundup Ultra Max (post-emergence) followed by post-directed spray of Roundup Ultra Max and 2) Broadcast application of Roundup Ultra Max (post-emergence) followed by post-directed spray of Roundup Ultra Max. Plant growth regulator (PGR) treatments were 1) Pix Plus/BAS, a new PGR, and 2) mepiquat chloride, the original PIX. Weed control was observed during the growing season and lint yield was determined after harvest. A total of 15.1 inches of water was applied through the sub-surface drip irrigation system.

Results: Due to very low rainfall and subsurface drip irrigation, pigweed pressure was light and both the Prowl + Roundup UltraMax and the Roundup UltraMax only scenarios provided effective season-long weed control (Table 1.). Similar cotton yields were produced with either PGR treatment. FiberMax 989 BG/RR produced the highest lint yield at 2069 lb./ac.

Table 1. The effect of two herbicide treatments on pigweed adn venice mallow weeds and on lint yield of Paymaster 2326 BG/RR and Fiber Max 989 BG/RR cotton.
Treatment Weed Control July 31 (%) Cotton Yield (lb/ac)
Pigweed Venice Mallow Paymaster Fiber Max
2326 BG/RR 989 BG/RR
Prowl + Roundup Ultra Max 100 a1/ 100 a 1746 a 1962 a
Roundup Ultra Max only 100 a 100 a 1806 a 2069 a
1/Means followed by the same letter do not significantly differ (P=0.05, LSD)





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