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Volume 7, Number 4 - April 2001

This Month in Ag Connection

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Timing of Roundup Applications to Roundup Ready Soybean

Alarm clock

The first post emergence Roundup application should be targeted on 4-8 inch tall weeds to avoid crop yield losses due to weed interference, and reduced control of larger weeds. We have observed an increase in the number of fields treated when weeds are 10 inches tall or greater. This can reduce effective weed control and lower yields. An initial application of 1 quart per acre (3 lb acid equivalent formulations) on 4-8" weeds is recommended. This is usually 3 to 5 weeks after planting. If new flushes of weeds occur, they can be controlled by subsequent applications. Roundup may be used up to 2 quarts per acre in any single in-crop application for control of annual weeds, where heavy weed densities exist.

(Adapted from information written by Dr. Bill Johnson, State Extension Weed Specialist. Click here to see more information.)

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Check Your Grain


As the temperature warms in the spring, it is important to monitor stored grain temperature and condition. Temperature differences between the grain and the outside air will cause moisture migration within the bin, causing grain spoilage. Grain along the bin wall will warm while grain near the center will remain cold. Air will migrate upward along the bin wall and move downward in the center. Grain spoilage will occur at the bottom center of the bin under spring conditions. Spoilage in fall will occur at the top of the bin since air movement is opposite that of spring. Grain should be warmed when the average outside air temperature is 10 to 15 degrees warmer than the temperature of grain in the bin. Run the fan continuously until the entire bin of grain is warmed to the average daily temperature. Repeat the warming cycles until the optimum spring and summer storage temperature of 50 to 60 degrees F is reached.

(Author: Don Day, Ag. Eng./Info. Tech. Spec.)

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High Corn Yields Are In The Details

Corn cob

Herman Warsaw, the Illinois farmer who held the world record corn yield of 370 bushels since 1985, finally lost the title in 1999. An Iowa farmer named Francis Childs entered the 1999 National Corn Growers Association Corn Yield Contest and officially made 393.7 bushels per acre without irrigation. This proves that corn grown in the right environment and with near perfect conditions can produce exceptional yields. Some believe that the average corn yield will need to reach 300 bushels by 2025 to meet the world demand. The current national average yield is around 125 bushels.

What does it take to make exceptional yields? One of the most important factors is the environment. Obviously Childs and Warsaw had ideal weather conditions in the years they reached their record. Corn needs about 25-30 inches of timely rainfall during the growing season and requires a moderate day and night temperature during pollination. When the day-time temperature exceeds 95 F during pollination, 1.5 bushels per day are lost. Advancements in genetics have contributed to improved corn yields (1.5 to 2 bushels per year since hybridization was introduced). Biotechnology has further improved yield by protecting the crop from stresses such as insects and weeds. Genome research at the University of Missouri is helping map chromosomes and gene interactions that impact yield.

A few things stand out about Francis Child's corn production.

While Mr. Childs used an extremely high rate of nitrogen to produce record-yielding corn in his test area, it's important to fine-tune exactly how much nitrogen your crop needs and to spread it in multiple applications so excess nitrates will not be a threat to groundwater.

Growers should take the time to gradually whittle away at limitations to their corn crop by paying attention to detail on a field-by-field basis since every field is different. Blanket approaches to growing corn will go unrewarded.

Make sure that a return is received on all inputs into the crop. It will take time to get all your yield-enhancing "ducks in a row". The first step is to set attainable goals and work toward them, keeping close financial records and guarding against possible environmental impacts along the way.

(Author: Tim Schnakenberg, Agronomy Specialist)

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Soil Test and Plant Analysis Summary for Year 2000

Man with a test tube

The University of Missouri Extension Soil Testing labs analyzed about 34,000 soil samples in 2000. Of these, 22,218 were for field crops, 4,403 for lawns and gardens, 826 for commercial fruits, vegetables and turf, and about 6,500 for research. The lab also analyzed 1288 plant samples, 67 water samples, 63 compost samples, 4037 special soil tests (tests other than regular/routine fertility tests). The data has value as a broad assessment of the nutrient status of soils throughout the state of Missouri. A complete report of the Soil Testing Lab can be obtained by contacting Dr. Manjula Nathan at (573) 882-6301.

Crops grown in Missouri generally require a pHs of 5.4 or more for non-limiting growth. Neutralizable acidity is determined by the Woodruff Buffer Method. (Note: Dr. Woodruff will turn 91 this April and at this writing continues to contribute to the University of Missouri from his office in the Natural Resources Building). About 21% of the samples tested lower than pHs of 5.4 (Table 2). About 14% of the samples from corn and soybean fields had pHs ranging from very low to low. The desired phosphorous (P) soil test level for corn and soybean is 45 lbs/acre. For corn and soybean, the desired potassium (K) soil test level for soils with a cation exchange capacity (CEC) of 15 would be 220 + (5 x 15) = 295 lbs. of K/acre.

Table 1. Percentage of samples with pHs ranges for corn & soybean fields
CropTotal< 4.44.5-5.35.4-6.06.1-7.5>7.5
Corn (grain)450711334520

Table 2. Percentage of samples within OM ranges for corn & soybean fields
Corn (grain)45074314021

Table 3. Percentage of samples within P ranges for corn and soybean fields
Corn (grain)450768282830

Table 4. Percentage of samples within K ranges for corn & soybean fields
Corn (grain)450703293829

Plant Analysis:
Corn is the crop tested most often among field crops with samples collected at different growth stages for analysis. Soybean is the second most frequently tested field crop. The regular plant tissue test includes N (nitrogen), P, K, Ca (calcium) and Mg (magnesium) and deficiencies were often observed. Corn stalk nitrate tests are done at the black layer stage to evaluate prior growing season N management practices. Click here to view UMC Guide G9131.

The most common problem observed was K deficiency. While some corn samples that were submitted from Northwest part of the state had high K testing soils, they still showed K deficiency. Moisture stress and compaction likely resulted in reduced uptake of K in these fields. Based on plant tissue testing data from the University of Missouri Soil and Plant Testing Laboratory, the incidence of K deficiency in corn and soybean increased from 1998 to 2000. These results indicate that a high proportion of Missouri farmers are at risk of experiencing K deficiency under appropriate environmental conditions. Plant tissue tests help diagnose problems and improve management decisions.

(Author: Todd Lorenz, Horticulture/Agronomy Specialist)

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Taxation Tidbits: Agricultural Inputs -- Exempt from Missouri Sales Tax or Not

Farmer on a laptop

The majority of the inputs purchased for use in production agriculture are exempt from Missouri sales tax. Do you know which inputs are not exempt? The Sales/Use Tax Auditors Training Manual defines exemptions which include:

Section 144.030.2(22) exempts: all sales of feed additives; propane, natural gas, electricity or diesel fuel used exclusively for drying agricultural crops; and farm machinery, if they meet a three-part test. The components of the test are:

Historically, items had to be tangible personal property at the time of title transfer to qualify. Items that were physically affixed to real property and therefore lost their character as tangible equipment at the time of transfer did not qualify for the exemption. For example, the sale of portable grain bins was exempt, but the sale of non-portable grain bins was taxable. machinery was exempt, whether or not such machinery or equipment is attached to a vehicle or real property. The rule on bins currently makes the distinction whether it is used during or after production. Feed storage bins are exempt, and grain bins are considered taxable. Repair and replacement parts purchased for use on farm machinery are exempt from tax. Consumable supplies such as grease, oil and antifreeze are not considered parts and are taxable items.

Effective August 28, 1998, Senate Bill 936 added the following exemptions to section 144.030.1(22):

Click here to view the Sales/Use Tax Auditors Training Manual on the web.

In addition to providing criteria and some rationale for why some items are exempt while other items are not - the site provides a link for two fairly comprehensive lists that set forth items that generally do or do not qualify for the agricultural exemption.

(Author: Parman R. Green, UO&E Farm Business Mgmt. Specialist)

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Publishing Information

Ag Connection is published monthly for Central Missouri Region producers and is supported by University of Missouri Extension, the Commercial Agriculture program, the Missouri Agricultural Experiment Station and the MU College of Agriculture, Food and Natural Resources. Managing Editor: Kent Shannon.