Experiment 439, Long-Term Application of N, P and K in Cotton, Altus, Oklahoma

Abstract

Fertilizer use in cotton production remains an important issue, especially in continuous cotton where farmers commonly apply the same rates year after year. This experiment was initiated in 1972 to evaluate the long-term effects of N, P and K fertilization on lint yield and lint quality. Each year, N, P and K fertilizers (depending on the treatment) were surface applied and incorporated prior to planting. Cotton yields were determined using a machine stripper. Lint yields peaked at the 40 lb N/ac rate with or without P and/or K fertilization. Although some increases in lint yields were observed in selected years at the 80 lb N/ac rate, increased N above 40 lb N/ac in the irrigated cotton study was not significant. Limited differences in P and K fertilization were noted from 1972 to 1999. One of the largest differences noted over the years was in yield potential as a result of changing varieties. Most recently, the use of Paymaster (145 and HS26) varieties have shown significant increases in lint yields, exceeding 1000 lbs/acre. This long-term experiment clearly shows that N applied at the 40 lb N/ac rate (when soil test P or K are adequate) resulted in near maximum lint yield.

Experiment 439 was initiated in the spring of 1972 to evaluate the long-term effects of N, P and K on cotton yields at the Irrigation Research Station near Altus. This study along with 222, 406, 407, 501, 502, 503, 504, 505 was started by Dr. Billy Tucker, and continued by Dr. Robert L. Westerman. The Irrigation Research Station is located in the Lugert Altus Irrigation District (LAID), which consists of surface impoundment by the Lugert Dam of some tributaries of the North Fork of the Red River. Irrigation at the research station is accomplished by utilizing concrete ditches, with water furrow applied via siphon tubes. The irrigation district allocates irrigation water to the research station as it does to local producers, with the amount varying each year as to the supply available in the reservoir. Large unlined earth canals are used to distribute the water to the various areas within the district. Some farms near these canals experience drainage problems associated with canal seepage which adversely affect crop yields. Underground tile drainage (installed in the late 1970’s) has been employed to facilitate lowering of the water table. The objective of this experiment is to determine the effect of long-term applications of N, P, and K on lint yield and cotton quality.

Procedures

Experiment 439 was established in 1972 on the western side of the Irrigation Research Station on soil that had previously been in continuous cotton under conventional tillage since approximately 1964. This soil was classified as a Tillman-Hollister clay loam (fine, mixed, thermic Typic Paleustolls). Soil test characteristics in from the 1988 for selected treatments are listed in Table 1. Each plot within the experiment has received annual applications of fertilizers at the rates indicated in Table 2. The N, P, and K fertilizer sources used are ammonium nitrate (33.5-0-0), triple super phosphate (0-46-0) and potassium chloride (0-0-62), respectively. The plot dimensions are six rows wide (40 inch row spacing) by 60 feet in length. The experimental design is a randomized complete block with four replications. Irrigation is applied as available, with allocations from the Lugert Altus Irrigation District varying from year to year. Since the irrigation water is furrow applied, the amount applied per application would be approximately 3 to 4 acre-inches. Cultural practices and other information pertaining to the experiment are found in Table 3. In the early years of the experiment harvest was accomplished by hand pulling the center two rows of the plot by 50 feet in length. In 1976 harvest was performed by machine stripper harvesting the rows. Beginning in 1983, grab samples were collected from the harvested material in each plot and ginned on small ginning equipment in order to approximate lint turn out or ginning percent. Also beginning in 1983, boll samples were taken, ginned and fiber properties on these lint samples determined by appropriate procedures.

Table 1. Treatment applications and experimental management for Experiment #439, Altus, OK, 1972-1999.

Year	Fertilizer Application Date	Planting Date	Variety	Seeding Rate lb/ac	#of Irrigations	Harvest Date
1972	5-15-72	5-31-72	Stoneville 213	22	3	12-22-72
1973	5-16-73	5-25-73	Stoneville 213	22	3	No Data
1974	5-10-74	5-30-74	Stoneville 213	22	2	12-18-74
1975	5-19-75	5-16-75	Lankart LX-571	21	1	12-3-75
1976	5-12-76	5-18-76	Lankart LX-571	20	5	11-19-76
1977	4-8-77	5-17-77	Lankart LX-571	21	2	11-18-77
1978	8-7-78	5-10-78	Westburn M	21	4	12-7-78
1979	5-17-79	5-31-79	Westburn M	21	1	12-7-79
1980	7-24-80	5-22-80	Westburn M	21	6	12-2-80
1981	7-16-81	5-23-81	Westburn M	20	1	12-2-81
1982	5-19-82	5-20-82	Westburn M	21	4	1-11-83
1983	5-11-83	6-1-83	Westburn M	21	7	12-9-83
1984	4-26-84	5-24-84	Westburn M	21	5	1-1-85
1985	5-17-85	5-17-85	Westburn M	21	4	12-21-85
1986	5-10-86	5-23-86	Westburn M	18	3	1-6-87
1987	5-11-87	5-13-87	Westburn M	18	4	12-2-87
1988	5-4-88	6-21-88	Westburn M	18	6	11-30-88
1989	4-27-89	5-23-89	Paymaster 145	16	3	11-8-89
1990	5-14-90	5-15-90	Paymaster 145	21	2	11-2-90
1991	3-11-91	5-28-91	Paymaster 145	21	4	12-5-91
1992	5-5-92	7-1-92*	Paymaster 145	17.8	1	2-1-93
1993	3-25-93	5-27-93	Paymaster 145	17.6	5	11-30-93
1994	4-21-94	5-10-94	Paymaster 145	18.4	5	10-4-94
1995**	5-3-95	5-16-95	Paymaster HS26	16.2
1996	4-25-96	5-9-96	Paymaster HS26	17.2	3	11-7-96
1997	4-22-97	5-14-97	Paymaster HS26	17.2	2	10-31-97
1998	4-23-98	5-19-98	Paymaster HS26	17.2	7	10-9-98
1999	5-14-99	5-19-99	Paymaster HS26	17.2	5	10-21-99

* initial planting date 6-11-92 ** crop lost due to hail storm

Figure 1. Mean lint yields for selected treatments using the variety, Stoneville 212, 1972-1974, Altus, OK.

Figure 2. Mean lint yields for selected treatments using the variety, Lankart LX-571, 1975-1977, Altus, OK.

Figure 3. Mean lint yields for selected treatments using the variety, Westburn M 1979-88, Altus, OK.

Figure 4. Mean lint yields for selected treatments using the variety, Paymaster 145, 1990-1994, Altus, OK.

Figure 5. Mean lint yields for selected treatments using the variety, Paymaster HS26, 1995-1999, Altus, OK.