Evaluation of Planting Date Effects on Crop Growth and Yield for Upland and Pima Cotton, 1997

J.C. Silvertooth, Plant Sciences Department
E.R. Norton, Plant Sciences Department
P.W. Brown, Soil, Water and Environmental Science Department

Abstract

Three field studies were conducted in 1997 at the Maricopa (1,175 ft. elevation) and Marana (1,974 ft. elevation) Agricultural Centers to evaluate the effects of three planting dates on yield and crop development for three representative Upland varieties. Planting dates ranged from 13 March to 8 May and also 312-1159 HU/Jan 1 (86/55° F thresholds). Crop monitoring revealed increased vegetative growth tendencies with later plantings. General trends also showed decreasing lint yield with the later plantings for all varieties at each location.

Introduction

There are numerous factors that contribute to the realization of a successful cotton crop, which could involve Upland (Gossypium hirsutum L.) or Pima (Gossypium barbadense L.) varieties in Arizona. Two major management decisions, variety selection and planting date management can have a profound effect on the development and final outcome of the crop. Selection of a specific variety will have a large impact on the way in which planting date should be managed. Similarly, the time frame in which a crop can be planted due to weather and/or other circumstances should have a large impact on the selection of a suitable variety.

Previous research in Arizona has shown that delayed plantings often result in higher vegetative growth tendencies at the expense of yield. Optimum planting date windows have been developed for different variety maturity groups (Figure 1) based upon heat units accumulated from January 1 (Silvertooth et al., 1989; Silvertooth et al., 1990; Silvertooth et al., 1991; Silvertooth et al., 1992; and Silvertooth et al., 1993; Silvertooth et al., 1994; Unruh et al., 1995; Norton et al., 1997; and Silvertooth et al., 1997). Planting date management not only has a large effect on crop growth, development, and yield but also impacts insect pest management (Brown et al. 1992, 1993, 1994, 1995, 1996, and 1997). Reduced season management, of which early planting plays a major role, has become increasingly important in recent years. The ability to get a crop in early, carry it through the primary fruiting cycle in a timely and efficient manner, followed by early termination; has become increasingly important with increased late-season insect pressures in Arizona. This approach to earliness management has also been important in terms of avoiding inclement weather conditions commonly associated with the summer monsoon season, which creates higher humidities (higher dew point temperatures) and higher night temperatures, resulting in accelerated rates of fruit loss and abortion.

Another method used for insect pest management is delayed planting. Delayed plantings have been utilized by many producers in some parts of Arizona to aid in the management of pink bollworm (Pectinophora gossypiella (Saunders)) populations. Delayed plantings are intended to encourage suicidal emergence of overwintering pink bollworm populations, theoretically lowering early season infestation levels.

The objective of this study was to further evaluate planting date windows and use the information for the validation and revision of recommendations. This evaluation involves an investigation of the effects of planting date management on the growth, development, and yield of cotton.

Methods and Materials

Studies were conducted in 1997 at the University of Arizona Maricopa (1,175 ft., Casa Grande sandy loam soil) and Marana (1,974 ft.) Agricultural Centers. The experimental design at both locations was a split-plot within a randomized complete block design. The mainplots were planting dates with subplots being varieties. Each subplot consisted of 8, 40 inch rows that extended the full length of the irrigation run (approximately 600 ft.). Planting dates were constructed so as to have three representative points along the recommended planting date range (Figure 1). Table 1 summarizes planting dates and respective heat units accumulated since 1 January (HU/1Jan., 86/55° F thresholds). Varieties selected for this study (Table 2) ranged in maturity from a short season, determinate varieties (STV 474) to more indeterminate varieties (DP 5415 and DP NuCOTN 33b). All plots were planted into moisture across all varieties and planting dates at Marana. At Maricopa, plots were dry planted and watered-up. All inputs such as fertilizer, water, and pest controls were managed on an as-needed basis.

A complete set of plant measurements were collected from all plots at each site on 14 day intervals. Measurements taken included: plant height, number of mainstem nodes, first fruiting branch, total number of aborted sites (positions 1 & 2), number of nodes above the top (1st position) white flower, canopy closure, and number of blooms per unit area. Climatic conditions were also monitored using an Arizona Meteorological network (AZMET) site located on each of the stations.

Irrigation termination dates are listed in Table 1. Lint yields were obtained for each treatment by harvesting the entire center four rows of each plot with a two row mechanical picker. Seed cotton subsamples were collected for ginning, from which lint turnout estimates were made. Results were analyzed statistically in accordance to procedures outlined by Steel and Torrie (1980) and the SAS Institute (SAS, 1988).

Results

Lint yield results for all PD and variety combinations are presented in Tables 3 and 4 for Maricopa and Marana, respectively. Fruit retention (FR) and plant vigor estimates (height to node ratios, HNR) patterns are shown in 2 through 7 for all PD, variety, and location combinations.

Vegetative growth tendencies, as noted by higher HNRs, have proven to be consistently associated with later plantings, were observed at all three locations in this study. This trend is well illustrated in these studies (Figure 3 and Figure 6) and it is generally true with all varieties, but it is most pronounced with STV 474 (a more determinate variety). The increased vegetative growth tendencies for the later plantings, as shown with HNRs, were apparent throughout most of the season.

Early FR levels were slightly higher for the later date of planting at both Maricopa and Marana, (Figure 2 and Figure 5). However, FR levels for the later date of planting dropped substantially at about peak bloom (~2000 HUAP) and beyond for all varieties at both locations. This was probably due in part to a greater portion of the fruiting cycle being subject to inclement weather conditions associated with monsoon season, which began near the end of July or first of August. Final FR levels were generally much higher at the end of the season with each of the varieties planted on the first PD, which corresponded to final yields as well.

Main effects associated with date of planting and variety were significant (P<0.05) with respect to yield at both locations. Interaction terms were also significant at each location. Differences among planting dates for each variety are shown in Table 3 and Table 4.

DP 33b, which is a transgenic Bt cotton, and its recurrent parent DP 5415, each demonstrated a classic response for a long-medium to full season variety with significant yield reductions associated with later planting dates. In most cases yields were higher with DP 33b than DP 5415. Also, DP 33b experienced less yield decline with later planting than DP 5415. These differences were attributed to pink bollworm damage suffered in the DP 5415, even with control measures being applied through conventional chemical insecticides, particularly with later planting. Agronomically, DP 33b and 5415 behaved very similarly in terms of growth and development patterns (HNR, FR, NAWF, etc.). In general, the more determinate variety (STV 474) experienced less yield reduction with delayed planting compared to DP 5415 or DP 33b.

Summary

The delayed plantings generally demonstrated higher vegetative growth tendencies as noted by HNR measurements. This pattern is consistent with earlier research (Silvertooth et al., 1989; Silvertooth et al., 1990; Silvertooth et al., 1991; Silvertooth et al., 1992; and Silvertooth et al., 1993; Silvertooth et al., 1994; Unruh et al., 1995; Norton et al., 1997; and Silvertooth et al., 1997). A lint yield decrease was commonly seen for all varieties from PD2 to PD3 (with the exception of STV 474 at Maricopa). Highest yielding potentials are usually realized with an early, optimum (includes optimum soil temperatures) planting date and a medium to full season type variety. In a delayed planting situation, a higher yield potential can often be realized from a more determinate, shorter season variety. These results also indicate higher yield potentials can be maintained with a late planting using a more indetetminate variety with transgenic Bt properties for pink bollworm protection.

Acknowledgements

We gratefully acknowledge the financial support provided by the Arizona Cotton Growers Association and Cotton Inc., and the valuable assistance from the personnel at the Maricopa and Marana University of Arizona Agricultural Centers. Also the technical assistance provided by Eric Norton, Justin Smith, Steve Ozuna, John Griffin, and Abraham Galadima is greatly appreciated.

References

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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.
This document located at http://ag.arizona.edu/pubs/crops/az1006/az10061b.html
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