Cotton
Mapping
Crop Monitoring - Plant mapping does not have to be complicated to provide useful information. In fact, the simpler you make it, the more likely you are to do it regularly. As the crop starts into the fruiting cycle, monitoring it's development can be advantageous. During the past few years there have been literally volumes written about crop monitoring. I think one of the biggest mistakes made in practical crop monitoring is the attempt to gather too much data. Crop monitoring for research and development is one thing, crop monitoring for management is yet another. The more complicated a monitoring system becomes, the less likely growers, consultants or fieldmen are to do it at all. The simpler a plant monitoring system is the better it is. With just a little thought and little knowledge of the cotton plant, plant monitoring can be both simple and helpful.
A simple method
for practical application is to break the growing season down into stages.
For cotton it makes sense to break the season into pre-square (from emergence
to first square), square set ( from first square to first bloom), bloom
(from first bloom until cut-out) and post cut out (from cutout till defoliation).
For simple purposes we should define cut out as the point when the field
reaches node above white flower five. Also, for clarification a field
should be considered at a particular event (emergence, square , bloom
NAWF -5 , etc) when at least 50 percent of the plants in the field are
at that stage.
After dividing the season into "management" periods, parameters to be monitored and measured should be determined. You may wish to customize these measurements to your own needs. However, once they are set they should be monitored uniformly and timely. The key factor is to not waste time monitoring parameters that you either can't interpret or can't use in making management decisions. Here are a few of the things that I look for during particular "management" times.
PRE-SQUARE - Until plant monitoring programs were developed and encouraged, few observations were made prior to squaring. If you are scouting for insect damage, that will be the principle thing you look for. However, if you are looking at other aspects of the crop, here are some examples: plant population, plant height, number of nodes, and root health. Other important observations that can be noted are; herbicide damage, missing rows, poor drainage areas etc. These parameters can be measured very quickly. In fact, plants can be pulled and these measurements made as you walk across the field. Analyses is also very quick and can be done on the turn row before moving to the next field. When summarized, the data can give indications of plant stand, stand uniformity and growth rate or vigor. This data can then be used to make replant decisions, help with insect control decisions and build a firm understanding of what type crop exists in the field. It should give an experienced manager a head start working with the field.
SQUARE - Until recently, insect scouting began at the initiation of first squares. Now it is common to begin scouting at emergence. However, it was only after the evolution of a simplified plant monitoring programs that crop parameters other than insects could be monitored during this phase. Here again, measurements taken must be simple and be made very fast. Care should be taken to be sure enough plants are sampled to give an accurate picture of the field. A suggestion is to take a minimum of five plants from four locations in the field. These can be accomplished as fast as you can walk across the field. Some of the important plant parameters which should be measured during this phase are: plant height, number of nodes, node of first square or fruiting branch, and number of squares retained in the first and/or second position. From this, numerous calculations can be made. Height node ratio and growth rate can be calculated and used in plant growth regulator decisions. Percent square retention can be calculated and used to help determine insect control thresholds and control strategies. Height, node of first fruiting branch, total nodes and square retention are the key measurements. Node of first fruiting branch will indicate timeliness of season. Total nodes can age the crop. In fact, I can get a much better image of the field situation if the caller tells me that they have a problem and the cotton has 12 nodes rather than saying the crop is about four weeks old. Percent square retention is critical to making sound insect control decisions. It is important to keep this data current as I feel it is very important to note "changes" in fruit set and growth. Growth rate can also be used as a management tool or as an indication as to how the crop is responding to its environment and used to help predict the need for plant growth regulators
BLOOM - It is during this phase that plant monitoring has the greatest opportunity to be beneficial to a crop manager. As the crop moves into bloom, plant size is getting larger. If you do not concentrate only on the keep components, you will get lost in the exercise, confused, frustrated and quit. During bloom the important things to measure are plant height, number of nodes, the number of nodes above the upper most first position white flower (NAWF), first position squares retained above the white flower and first position bolls retained below the white flower. If detail records are taken, plant height should be taken from the same plants from which nodes and fruit counts are made. Now, from a practical stand point - plant height can be taken by "observing" or measuring a few plants that are typical of the field. NAWF, square retention above the white flower, boll retention below the white flower and number of fruiting branches that have bloomed are the most important measurements and can be made within a few seconds without even pulling up the cotton. These measurements can be taken very fast, increasing the likelihood of their application. If these measurements are taken and used, they can provide powerful information about the field.
At first bloom NAWF should be in the range of eight or nine and square retention should be above 80percent, preferably around 90 percent. As the season progresses the white flower will move up the plant. As a boll load develops and competes with the vegetative component for carbohydrates, the white bloom will advance toward the terminal. By the second to third week of bloom, with a normal boll load, NAWF will be in the six to seven range and should hold there until the end of the fourth week or first of the fifth week of bloom. At that time it should advance to five and drive on out to three or four. The crop is essentially at cut when it his NAWF -5. That is assuming a normal fruiting pattern. Monitoring changes in NAWF, square retention and boll retention can provide valuable information about crop development. NAWF, plant height and boll load can be very valuable in making PIX decisions. Example: If the NAWF at first bloom is greater than nine it can be an indicator that the crop has tremendous vegetative horsepower. If square retention is low, or if boll retention is low, excessive growth will be a problem if the field is not checked. Likewise, if NAWF is low at first bloom, it is an indicator that stress has limited growth. The NAWF measurement is an indication of the horse power in the plant. The concept of NAWF coupled with a measure of fruit retention, is a powerful tool in plant monitoring.
POST-CUTOUT - Several factors can be monitored during this phase. Boll retention, regrowth and boll opening are the most notable. A concept called nodes above cracked boll (NACB) has been developed to aid in harvest aid application timing. This simply tracks the progress of the first position cracked boll as it moves up the plant and relates to the number of nodes above this measurement. This should contain a physiologically mature boll. Hence, another tool to help time defoliation.
Common sense must be applied in all situations.
