Project Summaries

12-138AL  Project Manager: D. C. Jones


Charles C. Mitchell, Auburn University

The "Old Rotation" experiment is the oldest, continuous cotton study in the world and the third oldest field crops experiment in the U.S. on the same site. The history of this experiment was published in 2008 in the centennial issue of Agronomy Journal.

An all-time record cotton yield of 2140 lb. lint per acre (~4.3 bales) was produced using only 120 lb. fertilizer N per acre. Corn and cotton yields reflect N availability more than any other factor. Long-term yields suggest that a winter legume would produce almost as much cotton as 120 lb. fertilizer N per acre. This year was an exception with extremely high irrigated yield potentials. Legume-only treatments produced about 3.5 bales per acre with irrigation. There was a dramatic response to irrigation by all crops. Non-irrigated corn yields in 2012 on plots receiving 180 lb. N/acre averaged 213 bu/acre with irrigation and 157 bu/acre without irrigation, a near-record yield for these plots. An additional 180 lb. N/acre increased gain yields ~ 100 bushels per acre over where only winter legumes (crimson clover) provide the N.

The Cullars Rotation is the oldest, continuous soil fertility study in the Southern U.S. In commemoration of the 2011 Centennial Year for this experiment, a comprehensive Ala. Agric. Exp. Station bulletin was published covering the first 100 years of this experiment. A poster was also presented at the 2012 Beltwide Cotton Conference. This study is non-irrigated and yields reflect growing conditions during that season. Note the dramatic yield response to added K. Highest cotton yields (1460 lb. lint/acre) were produced on the treatment receiving a complete fertilizer plus micronutrients (boron). No added P (Plot 2) dramatically reduces wheat, corn and soybean yields more than cotton yields. The Cullars Rotation Experiment is an excellent site to see dramatic nutrient deficiencies compared to healthy crops each year. This type of comparison does not exist anywhere else in the USA. Although this test is on a deep, sandy Coastal Plain soil (Marvyn loamy sand), the "no-S" treatment rarely shows S deficiencies on cotton and long-term yields indicate only a modest yield increase from applying S annually. This year was an exception in that dramatic S deficiencies were quite evident in cotton in mid-June. Leaf analyses confirmed a S deficiency (0.39% S in leaves from control plot #3 and 0.12% S in S-deficient leaves from plot #9). However, the final cotton lint yields on this treatment (1240 lb. lint/acre) was not dramatically different from a similar treatment receiving 40 lb. sulfate-S per acre (Plot 3, 1380 lb. lint/acre).


Project Year: 2012

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