Southern Region SSP has funded research studies that consider a variety of issues related to planting and tillage. The areas that research has focused on most extensively over the last 10 years include conservation tillage and optimum row spacing. Our survey considered various elements related to planting and tillage including: when to plant cotton, seeding rates, row spacing, planting methods and the use of conservation tillage.
We presented growers with a list of factors and asked to what extent each one determines when they plant cotton. Growers responded by circling numbers from 0 (not at all) to 3 (very much). An additional question asked growers about the ideal temperature for planting. A second series of items listed a variety of planting methods and asked growers to indicate the extent to which they use each one. They responded by circling a number from 0 (never) to 3 (always). An initial item on tillage asked what primary method the grower used. If growers were using some form of conservation tillage, they were then asked to indicate whether it had an impact on the profitability of their operation. Finally, two additional items focused on desired plant populations and row spacing.
Figure B - Factors Used to Determine When to Plant Cotton
Grower responses to items about the factors that determine when to plant cotton are depicted in Figure B. The figure shows the proportion of respondents who indicate this factor determines when they plant either moderately or very much.
An overwhelming majority of respondents (95.3%) said they relied on previous experience to determine when they plant cotton. Calendar date (78.3%) and predicted air temperature (79.5%) were heavily relied upon, and soil temperature, measured either by probe (57.6%) or estimated by hand (58.5%) was also commonly used. In contrast, 'other growers nearby' appears to have relatively little influence, with less than one-quarter (23.8%) saying this was a determining factor.
Nearly half of the growers (47.6%) believe that it is best to plant when the soil temperature is more than 65 degrees. Slightly less (41%) indicate that temperatures between 61-65 degrees are best. Only 9.6% said they believe 56-60 degrees was the optimal range, and less than 2% favored even lower temperatures.
Grower responses to items about what planting methods they use are depicted in Figure C. The figure shows the proportion of respondents who indicate they use this method often or always.
Figure C - Planting Methods Used
Precision depth seed placement was the most frequently reported method (80%). Use of even spacing was also relatively common, with 61.7% of growers indicating they use this method often or always. More than half (55.2%) use hill drop planting, while slightly less than half (48.7%) indicate they plant on ridges or beds. Use of skip row (1.5%) or twin row (1.2%) planting was extremely rare.
Grower responses to the item "What row spacing do you currently use?" are depicted in Figure D. The largest proportion of growers use either 38'' row spacing (49.2%), or 36'' row spacing (40.1%). The use of all other row-spacing was limited, with only 5.2% using 40" and 4.5 % using 30'' or less. According to growers in our survey, the use of narrow/ultra narrow row spacing is nearly non-existent (0.2%). A large majority of growers (81.7%) report trying to achieve a final plant population of between 2 and 4 plants per row foot.
Figure D - Row spacing growers currently use
More than two-thirds of growers (70.2%) report using some form of conservation tillage. For those growers who said they used conservation tillage, 63.7% said that using it had increased the profitability of their operation.
It is no surprise that growers rely heavily on previous experience for determining when to plant. The average respondent age is approximately 52 years and the average farming experience is about 29 years. The degree of reliance on calendar date is perhaps surprising since weather can be highly variable during late April through early May, the period considered normal planting time in many parts of the Southeast62. This apparent paradox may have resulted from the way the question was phrased. That is, growers have a sense of when they would like to plant (calendar date), but will watch the weather and delay if it is predicted to be cool or rainy.69
The substantial proportion of respondents who rely on soil temperatures (measured by hand or with a soil probe) and on predicted air temperature suggests that growers appreciate the effects of these variables on cottonseed germination and seedling diseases. This is critical for overall profitability as research has shown that yields can be reduced significantly when soil temperatures average less than 60° F 75. and that the optimal planting conditions are moist (not wet) soils, and a 4 inch soil temp of 65° F for 4 days, with warm, dry weather predicted.5
Edmisten 23 reported significantly higher pounds of lint per acre in conventionally planted cotton (4-6 seeds/row foot) than in any hill drop spacing (12, 18 or 24 inches between hills). Hill drop planting was nonetheless relatively common. The frequent use of hill drop seed placement by growers in our survey may reflect its potential value specifically on farms whose soils are fine textured.
Morton66 and Spurlock et al.92 reported that skip row planting can improve farm profitability. However, the very low use of this technique (93.9% Never used it) found in the survey is supported by results of Edmisten 23 who also found low adoption. Jost et al.44,45,46 also found that skip-row patterns generally reduced cotton yields, and that reduction in yield was greater in higher yielding environments.
Twin row planting was also rarely used (97.6% Never used it) by respondents. This is not surprising since research has indicated that the benefits of this approach are not consistently favorable. For example, one study 93 indicated that cotton planted in twin-rows may not have a detrimental effect on yield, while another 95 found no benefit from the practice.
Most growers report trying to achieve a final plant population of between 2 and 4 plants per row foot. This is consistent with University recommendations 5 that specify 3.5 seeds per row (resulting in about 2 plants/row ft.), and is also consistent with research that suggests a final stand of 3.0 to 4.0 plants per foot of row in 38 to 40 inch rows and 2.0 to 3.0 plants per row foot in 30 to 32 inch rows62. While one study determined that some growers have been reducing seeding rates in response to the documented increases in cotton seed cost over the past several years28. that finding was not confirmed by the results obtained in this assessment.
Several reports have noted equal or increased yields3 or better net returns 71 with ultra-narrow row (UNR) cotton. Our results, however, show very low use of both UNR and narrow-row (NR) spacing. This could be a reflection of seed cost, the limited availability of narrow row harvesting equipment (such as strippers or 15" pickers) inconsistent yields, and other difficulties such as high trash content and humidity effects with the use of finger strippers49, 14, 192. The frequent use of 38" and 36" spacing likely reflects availability of suitable machinery now on the farm, including harvesting equipment used by growers who rotate out of cotton to either soy or corn106. Given the prevalence of row spacing of 36" and 38", it is difficult to establish a link between SSP research, the use of NR or UNR cotton, and improved grower profitability.
Although many SSP projects have assessed effects of various planting dates and seeding rate on crop yield, we are unable to draw any direct conclusions about the contribution of this work to profitability at this time. However, we would suggest that knowledge gained by the individual researchers has likely diffused through the grower community and impacted grower understanding about what constitutes optimal planting conditions and seeding rates. This understanding in turn has likely affected the ability of growers to manage their cotton in a profitable manner. However, with specific reference to seeding rates, the increased cost of seed, suggests that continued support for refined knowledge on this topic would seem to be a good investment.
Given inconsistent or negative findings regarding profitability of Hill Drop or Twin Row planting methods, we interpret low adoption of these practices except under specific soil texture conditions as a positive outcome. Additional research to clarify the value of these planting methods is probably appropriate, however.
Although adoption is low, we suggest that SSP-supported research on NR or UNR row spacing has improved grower knowledge about the pros and cons of shifting to narrower spacing, and reduced the likelihood that growers would experience yield or quality loss from adopting an unproven or inconsistent technique and economic loss from purchasing new equipment. Particularly given the recent development and availability of a spindle picker for 15 inch row spacing102. we agree with the suggestion49 that farmers need more information about effects of lower than normal plant population densities to help them evaluate the economic feasibility of UNR cotton.
The widespread use of conservation tillage (CT) that we observed is consistent with other documented increases in adoption of this technique from 99.3 million acres in 1994 to 112.6 million acres in 200412. Most growers who use conservation tillage report that it has been profitable. In addition to the reduced soil compaction, reduced soil loss through erosion, and maintenance of soil structure that are a consequence of its use, CT also typically results in savings in operating costs such as fuel and labor.
An economic evaluation of conservation tillage systems in Texas revealed reduced production costs and higher net yields43. A $45.08 reduction in cost for no-till compared to conventional till was also documented in a separate analysis. These saving estimates were attributed to the use of smaller equipment, resulting in less repairs and maintenance, and reduced labor and fuel costs which more than offset the additional cost of herbicide. Yet another economic analysis78. claimed that the state of Georgia could achieve a benefit of $245 million associated with reduced erosion and improved water quality. When transgenic and non-transgenic varieties were compared under various cultural practices, it was determined that CT allowed significant savings on variable costs, and were more efficient and more profitable, particularly when combined with use of transgenic varieties. On occasion, the benefits of CT may be attenuated by increased damage from cutworm species that can build up on weed hosts or on leguminous cover crops40. There are, however, many additional studies showing that CT is the most profitable system.70,53, 35
It appears that SSP research on various forms of conservation tillage has been an appropriate use of their financial resources as these practices have been widely adopted and there is corroborating evidence from a variety of sources that conservation tillage promotes increased profitability for cotton growers. Further refinements in understanding the full benefits of conservation tillage, particularly regarding its use in the context of various crop rotations and its impact on pest management, may further increase adoption among those remaining southeastern cotton growers who still report using conventional tillage methods.