Date of Planting by Long Staple and Short Staple Variety Trial, Safford Agricultural Center, 1997

L.J. Clark, Safford Agricultural Center
E.W. Carpenter, Safford Agricultural Center


Four varieties each of Long Staple and Short Staple cotton were tested over five and four dates of planting, respectively, in this study. The first date of planting for the Long Staple cotton was pushed up to the 18th of March because planting is now legal in Graham county as early as March 15th. The latest planting was May 13th. Cultivars of differing maturities were tested for both long and short staple cotton to determine their optimal planting time. Many agronomic and hvi values were evaluated to determine the effect of different planting dates


A date of planting study had not been planted on the Safford Agricultural Center for many years and never before with long staple cotton varieties. The past few years with the coming forth of many new long staple varieties of differing maturities has necessitated this study. It is important to know the window of opportunity for planting different varieties as stands are lost, necessitating replanting and some years the spring weather doesn't allow planting in early April.

Methods and Materials

The varieties being tested were planted in a replicated small plot design with two rows of each variety being planted in four replicates at each planting date. The crop history is included below to define the cultural practices.

Crop history - Long Staple

Soil type: Pima clay loam variant
Previous crop: Cotton
Planting date: 18 Mar, 1 Apr, 16 Apr, 28 Apr and 13 May 1997
Rate: 25 lbs/ac
Herbicide: Triflurilin preplant incorporated, Cotton Pro at lay-by
Fertilizer: 110 lbs/ac urea side dressed 6/2, 100 lbs/ac urea side dressed 7/14
Irrigation: Watered up plus 8 irrigations (24 ac in + 6.0" rain)
Last date: 8 September
Harvest: 1st pick: 24 October        2nd pick: 4 November

Crop history - Short Staple

Soil type: Pima clay loam variant
Previous crop: Cotton
Planting date: 1 Apr, 16 Apr, 28 Apr and 13 May 1997
Rate: 25 lbs/ac
Herbicide: Triflurilin preplant incorporated, Cotton Pro at lay-by
Fertilizer: 100 lbs/ac urea under green manure crop 2/10, 100 lbs/ac urea side      dressed 6/3 and 7/14
Irrigation: Dates 1 and 2 planted into moisture, 3 and 4 watered up, plus 6      irrigations (24 ac in + 6.0" rain)
Last date: 6 September 1997
Harvest: 1st pick: 16 October       2nd pick: 4 November

Plots were harvested with a modified two-row cotton picker which collected cotton from each plot in a large bag. Weights were then obtained by weighing the bags on a hanging scale.

Results and Discussion

A two way analysis of the data on date of planting by long staple varieties is shown in Table 1. In looking at the varietal data across all dates of planting, few statistically significant differences are seen. Considerable differences were seen, however, in looking at the date of planting data over all varieties. The third planting date was the best, with higher yields, increased plant maturity at harvest, better lint turnout, tallest plants and fruiting started between the 4th and 5th nodes. Much seemed to be obscured by lumping all varieties together or all dates of planting together, so a number of tables are put together separating the date and variety effects. Table 2 shows the lint yields of long staple varieties by date of planting. This still shows the superiority of the third date of planting, but also shows S-6 and OA 312 had a little more tolerance for cold, in that they did better than the other varieties in the second date of planting. S-7 showed the greatest tolerance for the late April planting. Table 3 looks at the percent first pick by date of planting and variety. This can be used as an indicator of plant maturity at harvest. Early plantings delayed the plants maturity in the fall. This might relate to root damage done when the soil temperatures dropped into the mid to low 50's on the 26th of March and 4th and 5th of April. Late plantings were not as mature at the harvest date because they hadn't had sufficient heat units to drive the plant to full maturity. The two OA varieties did not do well in the latest planting, even though they are considered early maturing plants. Table 4 shows the percent lint turnouts. The best turnouts came at the optimal planting date. OA 361 had the best overall turnout but its value dropped off with the late planting. Table 5 shows first fruiting branch position. Varietal differences were seen but generally the second date of planting was the hardest on plants for setting fruit early. Table 6 shows fiber length. Oddly enough the best fiber came from the second planting date, which struggled with early fruiting. Pima S-6 seemed to have the most consistent fiber length over the planting period. Table 7 shows fiber strength. There were varietal differences over dates, S-6 had good strength with early plantings, OA 361 had good strength in the middle and at the end and S-7 maintained good strength through most of the plantings. Table 8 gives micronaire values. All of the values were in the acceptable range but differences were seen. The latest planting had the lowest readings, which is understandable from the fact that fewer heat units were received by the plants. The lower micronaire readings from the second planting is not fully understood, but may go back to the idea of root damage causing unthrifty plants.

Table 9 presents the yield data for the date of planting by short staple variety study. As with Table 1, this table gives yields for varieties across all dates of planting and for dates of planting across all varieties. The first date of planting was eliminated from this study because earlier work had shown the best yields from mid April plantings. These findings confirmed the earlier works. On varietal differences, DP 90 the longest seasoned variety produced the most lint, followed closely by HS 44. Table 10 show lint yields by date of planting. DP 90 shows good yield through the entire planting range with HS 44 and SG 501 showing strength in the middle of the planting range and STV 132 only coming into its own with the latest planting. Table 11 gives the lint turnout data. SG 501 was consistent across all dates of planting, the other varieties went up and down. No conclusions are drawn from this information. Table 12 shows percent first pick data. DP 90, being the longest maturity variety, was expected to have the lowest values across this table, that was not seen. The data show that all dates of planting except the last one were on equal footing, as far as maturity is concerned, at harvest time. The good heat unit accumulation during the middle of the season, had brought everything along together. Table 13 shows fiber length information for the short staple varieties. It is noted that fiber length was not particularly good in 1997. The values move around a bit with variety and date of planting, but nothing is concluded from this data. Table 14 give fiber strength data. As with the length, STV 132 was in a different class from the rest of the varieties, being consistently lower through all the planting dates. Strength varied by variety and date but nothing consistent to show any trends. Table 15 gives the micronaire data. HS 44 and STV 132 had the most consistent micronaire values across all planting dates. DP 90 and SG 501 showed a declining micronaire value with the latest planting, which would be consistent with less mature fiber at the end of the season.

The most significant thing shown in this study is that both long and short staple varieties produce best if planted when soil and air temperatures are favorable for physiological growth. This typically occurs in the Safford Valley in the third week in April. That was the case this year.


  1. Clark, L.J., E.W. Carpenter and J.C. Silvertooth. 1997. Date of planting by long staple variety trial, Safford Agricultural Center, 1996. Cotton, A College of Agriculture Report, The University of Arizona, Tucson, AZ. Series P-108, pp, 62-66.

This is a part of publication AZ1006: "Cotton: A College of Agriculture Report," 1998, College of Agriculture, The University of Arizona, Tucson,Arizona, 85721. Any products, services, or organizations that are mentioned, shown, or indirectly implied in this publication do not imply endorsement by The University of Arizona. The University is an Equal Opportunity/Affirmative Action Employer.
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