| Pinpointing Cotton's Nitrogen Needs | |||
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| The modern, successful farming operations in today's fast paced and ever changing world, have several sources of technology available.
To be cost effective, one method in growing cotton is Soil and Petiole Analysis. Implementing such a program can help you to pinpoint your nitrogen needs and to indicate the success or failure of your current fertilizer program. |
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| Points You May Need To Consider | |||
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| 1. Check Land, Water, Insect, Weed and Disease management practices | 2. Obtain soil samples for fertility and salinity analysis before planting | 3. Take petiole samples carefully prior to each irrigation or opportunity to fertilize | 4. Fertilize according to the needs of the crop |
Nitrogen fertilizer is applied to the vast majority of acres planted to cotton each year. Rates of application maybe as low as 50 pounds per acre, to over 300 pounds per acre. You can increase yields by the proper use of nitrogen on some fields. The objective of a good fertilizer program for any crop is to provide adequate but not excessive nutrients. The amount needed to fulfill this objective will depend upon initial soil fertility, the crop to be grown, date of planting, water management practices, physical condition of the soil, the climate, seed variety, disease problems and insect damage, but to name a few factors. Two tools that are utilized are Soil Analyses ahead of planting and Petiole Analyses beginning after two weeks are very useful.
Nitrogen is found in the soil in several forms. It may be in organic materials, in the ammonium form, or the nitrate form. The weather conditions cause the micro-organisms to convert the organic and ammonium forms to nitrate. Since the nitrate form is very soluble and moves through the soil with the irrigation water, the amount of nitrate nitrogen present varies widely. If soil samples are obtained properly and at the right time, the nitrate content of the soil can be used to help pinpoint early needs for nitrogen fertilization of cotton.
Nitrogen is contained in the various parts of a plant in different forms and amounts. To use tissue analysis successfully for pinpointing nitrogen needs in cotton, it is necessary to consider a single form of nitrogen in a specific plant part. The level of nitrogen in leaf petioles (the petiole is the stem that connects the leaf blade to the stalk) has been found to be the best indictor. Early in the season, the nitrate level in the petiole will be quite high if soil nitrogen is adequate. As the plant begins to form squares, then flowers and bolls, the level of nitrogen will decrease rapidly. Analyses to determine the nitrate content of petioles in a designated portion of the cotton plant can be used to help pinpoint the nitrogen needs throughout the season.
Take soil samples ahead of planting. Obtain soil samples after the pre-irrigation and prior to planting, and from the side of the cotton beds. Samples from the plants should be taken when the 1st squares begin to appear on the young plant, usually just prior to the 1st sidedress. Samples should then be taken a few days prior to each irrigation. You will need at least 25 - 30 petiole per sample. Select the youngest mature leaf on the plant, usually about the third or fourth leaf down from the top.
| When is fertilizing needed? | How much nitrogen has been applied? | When did the field last receive water? | What is the growth stage of the cotton? |
| What soil types are common in the field? | What kind of nitrogen has been applied? | What is the square and boll load? | Any unusual climatic conditions? |
| Has Pix been applied? How much and when? | What method of applying nitrogen was used and what were the last test results? | Are there any pink bollworms or white flies? | What has the phosphate-p level been doing? |
