The decision to replant is one of the most important decisions in crop production. This project is designed to evaluate several factors that are important in making a replant decision. Planting date is important since yields decrease with late planting. Low plant populations can decrease lint yields. Loss of leaves due to factors such as hail can cause a reduction in lint yield and delay maturity. It was found over a four year period May 5 was the optimum time for planting cotton and after May 21 major yield reductions can be expected. Usually replanting will be in the latter part of the month. Other crops would be better if replanting is necessary in June. Low plant population results in late maturity but the reduced yields of populations of one per 1.5 feet do not offset the effect of the late planting date upon lint yield. Loss of leaves at the four true leaf stage usually will not result in adequate yield loss to justify replanting. The data shows that replanting seldom pays and it is very important to achieve an adequate plant stand with the first planting.

One of the most critical decisions a producer must make is to determine if replanting is necessary. Several factors have to be taken into consideration such as replanting date, stand density and damage due to loss of leaves. Many producers replant when leaving the remaining stand would be the most profitable option. The purpose of this project was to obtain information that will enable producers to make better decisions.

This project was started in 2001 and continued through 2004 and is divided into three parts: planting date, plant population and leaf removal. Delta Pine 1218 BG/RR was planted. The experimental design was a randomized complete block with four replications for each of the three parts. Row width was thirty eight inches and plot length was thirty one feet and was end trimmed before harvest to eliminate end plant effect. Irrigation was by furrow and was irrigated when soil tension was a negative 55 centibars. Insects were controlled as needed. Thrips were controlled with Temik applied at planting. Mepiquat chloride was applied as needed. Soil test recommendations were used for determining the fertilizer rates. The soil type is a silt loam. The trials were harvested with a Case International two-row picker. The samples were ginned on a twenty saw Continental gin stand preceded by an inclined cleaner and a feeder extractor followed by one stage of lint cleaning. Samples were graded on a high volume instrument. Planting dates were started in late April and continued to late May or early June. The plant population plots were over seeded and thinned to the proper density. In the leaf removal study the leaves were removed at the fourth true leaf. Cotyledon leaves were not removed.

Four years of data show May 5 to be the optimum planting date for the Bootheel of Missouri. In 2002 any date in May produced similar yields. Yields started a decline in the other years starting at an early date of May 5 in 2001 until May 21 in 2004. In most years yields were around an average of 25% or more lower after May 25 except in 2002. This data certainly should discourage anyone from replanting.

Plant height and plant population increased at the later planting dates. The turnout and micronaire decreased with late planting. Length increased with late planting and in 2003 the elongation showed a significant increase. Significant increases were found in leaf content as would be expected with late planting.

Maturity is affected by spacing and it was evident in late September. Two per foot or more appears to produce the earliest crop. The lower plant populations have more vegetative branches which are typically late maturing. Growers trying to save money on engineered gene technology fees could have a problem in areas such as Missouri where the growing season is short. Lint yields were highest with two plants per foot. Yellowness drops with an increase in plant population.

There was a numeric increase in fiber length due to crowding, but we did not find a significant difference. There were significant differences in uniformity, but there was not a clear trend. Fiber strength was unaffected. Elongation showed a numeric improvement in the more ideal spacing of one or two per foot. Trash content and color were unaffected. Unless plant spacing is less than one per 1.5 feet it would not be wise to replant.

Leaves were removed at the fourth true leaf to simulate the effect of a hailstorm. This will not totally mimic the effect due to the lack of stem damage. Cotyledon leaves were not removed. One treatment involved removing the terminal but none of the leaves. In September it was easy to observe a delay in boll opening due to the leaf or terminal removal. There was a delay with the removal of one leaf and a greater delay with the delay of more of the leaves or the terminal. The effect of terminal removal is similar to removing 3.5 leaves. The drop in yield was similar to the delay in maturity. There was a yield decrease with the removal of one leaf and a significant drop with more than one leaf or the terminal. Turnout drops with a decrease in the number of leaves.

Micronaire dropped significantly with the leaf removal. Some levels of leaf removal caused enough yield loss to justify replanting in some instances.

The data suggests that replanting will seldom pay unless there is a significant loss of leaves or terminals. Even then it may not pay to replant unless replanting can be done in the first twenty days of May. A loss of stand will usually be offset by reduction of yield due to late planting.

In conclusion replanting will seldom pay unless there is a very severe loss of plant stand or the stubble left is in very poor condition. The data suggests that it is critical to get a stand with the first planting.

This project is funded by Cotton Incorporated.