ISSUE 3   May 29, 2008

ON FARM CROPPING TRIALS

It is a good strategy to evaluate new cropping practices on a limited scale on the farm before adopting the new technology on many acres.

Although published data from university research and other sources will indicate whether a practice will work and provide a financial return under the tested conditions, adapting the technology to specific fields and management systems requires local testing. Through careful testing and evaluation an agricultural producer can determine the economics of the product or practice and see if the change in practice will increase the farm profit.

Setting up proper field trials will require some careful planning to obtain meaningful results. Sometimes test strips do not follow proper protocol and there may be a bias for or against the new product or practice. Here are some guidelines for planning field tests.

Always compare the newly tested variable (product, variety, technology) against the current production practice.

1) The field test site should be as uniform as possible for the "current" and the "new" technology. Make sure the soil type, drainage, slope and location in the field are similar.

2) The size of the test area should be reasonably large to harvest enough crop so a weigh wagon can be used to determine yield differences. Excessively large plots such as 1/4 to 1/3 of a field may actually decrease the accuracy of the trial because too many variables affect the final results.

3) Test strips the length of the field are usually the most practical. They are easy to plant, manage and harvest. It is easy to change treatments such as herbicides, fertilizer, insecticides, fungicide rates or crop varieties.

4) One of the fundamentals in crop research is replication of observations. It is important to repeat treatments (control and whatever else is investigated) at least two times but preferably more.

5) Evaluate only one variable at the time and manage each strip trial exactly the same except for the variable evaluated. For instance if you are testing soybean varieties, each trial strip should have the same tillage, seedbed preparation, fertilizer application, weed and insect control during the season. The only difference would be the variety. Another example would be to use fungicides or insecticides as a treatment and compare them to the situation where no product is applied (an untreated control or check). In this way with replicated observations the yield potential of the different treatments can be established under the farmís unique set of environmental and management conditions.

6) Keep accurate and complete records of all field operations and observations. These records will help to validate comparisons between the treatments. Record exactly where the "treatment" and the check plots are located. Also record weather conditions, dates of seeding and spraying, crop stand, and any pests developing during the season.

7) Some farms have advanced technology available and use global positioning to plant and apply products to the field. At harvest combines with GPS systems will be able to record exact yield in the field with yield monitors and data on treatments can be obtained from the yield maps.

8) Producers who do not have yield monitors can use weigh wagons to establish the yield of the harvested area. The width in feet x the distance traveled in feet gives the harvested area and yield per acre can be calculated.

With high commodity prices there is an increase in products which claim to have positive yield effects. Use available research data to see if the product has merit. The next step is to try out the product on the farm under controlled conditions and after harvest evaluate if the yield increase of the technology tested will pay for the additional cost of the product and application cost.

If producers need help setting up trials or evaluating test results, contact North Dakota State Extension staff for advice.

Hans Kandel
NDSU Extension Agronomist
hans.kandel@ndsu.edu

 

GROWTH STAGING SMALL GRAINS

Most of the small grain crops in North Dakota have now been planted. Winter wheat is or will soon be jointing, and early planted spring wheat and barley are well established. The next few weeks are extremely

important in determining the yield potential of small grains as many of the components that make up yield develop early in the season. Timely application of management practices is critical to achieving high yields. Since crop growth and development are affected by the environment and by the variety, the recommendations for most management practices for which timing is important (e.g. fertilizer topdressing and herbicide application timing, etc.) are based on crop growth stage rather than calendar date. Therefore, being able to properly identify the growth stage of your cereal crop will be important to ensuring that management practices are applied at the appropriate time. In this article I will briefly review how to determine the early growth stages of your small grains.

Early Growth Staging in Small Grains

Growth stage scales have been developed and are commonly used by researchers when describing experimental methods and results in scientific publications, but less so in communicating recommendations to farmers. The timing of early-season management recommendations are most commonly based on leaf numbers or other visible characteristics of the plants. Therefore, in this article I will focus on how to assess these various characteristics and will not delve into the details of growth scales.

When growth staging your crop you should begin by obtaining a representative sample of plants from the field or part of the field of interest. To give you a good feel for an "average" plant, use ten plants selected at random away from the edges of the field. Remove any soil attached to the plant so that you are able to observe the roots and crown. Leaf stage is the most common physical feature used to describe early development of small grain crops. Leaf stage is defined by the number of leaves that have visible collars on the main stem. Care must be taken to ensure that the earliest leaves are included when counting. The first leaf is small and is frequently lost from the plant during normal growth. It has a characteristically blunt tip. Look for the sheath remnants at the crown of the plant if you suspect that the first leaf (or second for that matter) is missing. Count only the leaves on the main stem, which is the tallest and most leafy of the stems. Include only those leaves that have a collar. When staging plants include all leaves, even those that have been damaged by hail or frost. The total number of leaves that a plant will develop is more or less fixed for a given variety; leaves that are stripped from the plant will not be replaced by additional new leaves.

Predicting Leaf Stages in Small Grains

Sometimes it is useful to be able to estimate or predict when a certain growth stage will be reached. Plant development is closely correlated to the accumulation of heat units or Growing Degree Days (GDD), much more so than calendar days. Based on plant emergence and historic temperature trends, you can predict with fair accuracy when a crop will reach a certain developmental stage. Growing degree days are readily available for a number of locations in North Dakota using the NDAWN website (http://ndawn.ndsu.nodak.edu/). Wheat requires about 140 GDDs and barley about 100 GDDs to produce a leaf. The actual number of GGDs required can vary between varieties, but these values will give estimates that will be accurate enough for most applications. Be sure to use GDD that were calculated for small grains which use a base temperature of 32 degrees. Other base temperatures are used for corn and sunflower and certain pests.

As an example, if you wanted to know what stage your wheat crop would be in at the end of the week, you could estimate it by using either historical weather data or predicted weather data. Fargo accumulates about 29 small grain GGDs daily during the last week in May and 31 GGD per day during the first week of June. Using these data, you could expect wheat to produce 1.5 leaves during the last week of May and 1.6 leaves during the first week of June. Barley could be expected to produce 2 and 2.2 leaves per week during these same periods.

Joel Ransom
NDSU Extension Agronomist - Cereal Crops
Joel.Ransom@ndsu.edu


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