ABSTRACT

Plant mapping can be used throughout the growing season or at the end of the production season to evaluate the growth of plants and the effect of specific treatments or cultural practices on growth characteristics. The use of plant mapping produces large quantities of data which has to be summarized and analyzed in order to draw inference or conclusions about conditions in the field. PMAP and COTMAP are programs which have been written to assist in the summation of plant mapping data. These programs were used to summarize data from some of the field studies initiated to determine the feasibility of narrow-row cotton production. Included in these studies were nitrogen (N) management, plant growth regulators, potassium (K) rates and placement, and varieties. Only mapping summaries from the N management study will be included in this report. The objectives of the study included 1) determination of optimum N management by evaluation of N rates and application schedules; 2) field evaluation of PIX (mepiquat chloride) plant growth regulator; and 3) evaluation of plant characteristics and yield by plant mapping using COTMAP and PMAP. This report will focus on the third objective. The treatments included urea-ammonium nitrate solution (32% N), applied either 100% preplant (PP) or 50% PP and 50% as a sidedress (SD) application at early bloom. The N rates were 90, 120, and 150 lb/A knifed in on either side of the row. PIX was applied to one-half of the plot each year with rates of 4-6 oz/A. End-of-season mapping was done from three of the six replications, just prior to the first harvest in 1990, 1991, and 1992. Five plants from each Pix subplot were mapped giving a total of 10 plants for each N management treatment. Individual plants were enter and summarized by the programs. Statistical analysis was performed on the means generated from the individual plant summaries. Some manipulations of the files were required to assign modifying elements to the summary data. Information summarized included plant populations, plant height, first fruiting node, total fruiting nodes, total nodes, internode length, number of vegetative branches, boll numbers, boll positions, boll distribution, and boll retention. No mapping was completed for 1989, so data presented in the talk represents means for 1990 through 1992. There was little variation in plant growth related to row spacing. The 40-in row cotton was taller than 30-in cotton with height increased with N rate for 40-in rows but not for 30-in rows. There was no difference in first fruiting branch for 30-in cotton compared to 40-in cotton, indicating that 30-in row cotton is not early fruiting than 40-in cotton as has been claimed by some. Row spacing had little effect on the number of fruiting (sympodia) branches or the number of vegetative (monopodia) branches. The total bolls per plant was higher for 40-in rows in all years with the average equal to 1 boll/plant. Plant mapping has not detected specific regions of the plant that were affected by the increasing N rates. The total lint production loss in 40-in rows was apparently distributed throughout the plant. Plant mapping data does not support claims of earlier maturity for 30-in rows. Yield data has actually shown that 30-in cotton matured later than 40-in rows in some years. The two programs used, COTMAP and PMAP, have been useful in summarizing the volumes of data collected during plant mapping and the data discussed covers only a small portion of the output that is available. The output can also be used in spreadsheets to examine the distribution of lint on the plant and the dollar values associated with that distribution. More information will be summarized from the data and may be available at a later date.