Rainfall Management Is Critical For Dryland Cotton

Writer: Tim W. McAlavy, (806) 746-6101, email: t-mcalavy@tamu.edu

LUBBOCK – Dryland cotton farmers who manage their crop to make the most of rainfall and soil moisture stand a better chance of producing profitable yields than those who simply bank on adequate rainfall, according to a South Plains agronomist.

“Saving and managing soil moisture is the name of the game in dryland cotton,” said Dr. Dan Krieg, professor of agronomy at Texas Tech University. “As a result, we must use cotton production systems/techniques designed to reduce water stress during the plant’s critical development stages.”

Krieg was one of eight featured speakers at the Jan. 22 Caprock Cotton Conference in Floydada; one of six regional South Plains crop conferences sponsored each year by Texas Cooperative Extension in January and February.

“Our long-term annual rainfall averages somewhere around 20.4 inches. Most years, we receive about 70 percent of that total – or 13.5 inches – between April and October,” Krieg said. “Inside that April-October window we see a strong relationship between dryland yields and the amount of rain that falls from mid-June to mid-July.

“If our fields are set up to bank that moisture, we can provide dryland cotton with a much-needed drink of critical, yield-producing moisture.”

Many dryland producers rely on a skip-row system where two 40-inch rows of cotton are separated by a fallow, bare row. In theory, the fallow, or skip, rows in this system act as a moisture bank for adjacent cotton rows, but some are now questioning the wisdom of this system, Krieg said.

“If we leave a barren row of ground out there, we have created a zone with high evaporation potential. In the past few years, we have seen better, more consistent yields from cotton planted on 30 or 32 inch rows interspersed with grain sorghum,” he added. “In this system, we plant several rows of cotton and grain sorghum in adjacent strips to produce a field that is two-thirds cotton and one-third grain sorghum.

“We can rotate crops easily in this system and manage soil moisture at the same time. The grain sorghum residue helps reduce wind erosion and boosts rainfall infiltration. It also reduces evaporation of soil moisture by reflecting heat and sunlight, and reduces the incidence of soil sealing after a pounding rain by softening the impact of raindrops.”

Krieg said this system of combining crop rotation with soil moisture management could boost yield potential by as much as 100 pounds per acre.

He also advised producers to think beyond “maximizing yield” by focusing on plant health and fiber quality.

• When planting, think in terms of “plants per foot of row” rather than pounds per acre.

“Planting to achieve between three and four plants per foot of row is ideal. Higher plant densities encourage barren cotton plants (weeds) that rob productive plants of moisture and soil nutrients.”

• Time fertilizer applications to supply nutrients when rainfall occurs.

“Pre-plant fertilization with about 40-50 pounds of nitrogen per acre is a good bet. Spring rains will activate the nitrogen and carry it down to the plant roots. Base fertility on yield goal and soil tests, and remember the rule of thumb that it takes 30 to 50 pounds of actual nitrogen per acre to produce one bale of cotton.”

• Look at other factors besides yield potential when evaluating varieties.

“Look at lint quality ratings, too. Compare staple length, fiber strength, and micronaire (fiber fineness and maturity). There is an economic advantage in producing lint that rates 34-plus in staple length, with 28-30 grams per text (staple strength) and 4.0 average micronaire.”

Krieg challenged dryland producers at the Caprock Cotton Conference to “choose varieties for fiber quality and then manage it” to optimize both soil moisture and yield potential.

“Dryland cotton yields on the South Plains have been essentially flat over the last 30 years. But we can realize a yield advantage and an economic advantage by adopting production systems that preserve soil moisture and rainfall for crops with real fiber quality potential.”

The 2002 series of South Plains Extension crop conferences will wrap up with the Hale County Cotton Conference-Soil Fertility Day on Feb. 18, and the Sandyland Agriculture Conference in Gaines County
on Feb. 19.