Raymond C. Ward, Ph.D.
Jolene F. Ward, B.S.
|A Practical Look At Soil Productivity
By Dr. Ray Ward, Certified Soil Scientist
Every now and then, the professionals at Ward Laboratories, Inc. in Kearney, Nebraska are asked why two fields in close proximity to one another can produce dramatically different yields with the same type of management practices.
The coffee shop answer to that question may be bad luck … in reality, the answer may rest with soil productivity. The fact of the matter is, different soil types require different management practices to produce maximum yields.
I have had the opportunity to witness this process on our family farm in southeast Nebraska over the last 10 years. I have monitored the yields of these two dry land fields with a high producing silt loam soil and a lower producing silt loam with a clay subsoil. Over that decade of observance, soybeans ranged from 30.2 bushels to 49.2 bushels, while corn ranged from 100.1 bushels to 139.6 bushels.
In many cases the difference is a result of the soil’s ability to absorb water for the plant to use. In the lower yielding clay subsoil, water permeability may be as low as .06”/hour or 0.6” every 10 hours. Conversely, the permeability of the silt loam soil is .6”/hour or 6” over a 10 hour period.
The higher yielding silt loam field has an available water holding capacity of 2 1/2”/foot where the clay subsoil can hold only 1 3/4”/foot.
Simply put, more water holding capacity and better permeability translates into more water for the plant to use.
So, as producers establish “management zones” on their fields, soil types should be a major consideration in the development of plans to address production in those management zones. Different soil types require different management.
Additional information about soil types in your fields can be found at your local NRCS office through the County Soil Survey Manual.
Soybean Cyst Nematode Found Near Kearney
The first soybean field in central Nebraska to be recognized as being infested with Soybean Cyst Nematode (SCN) has been identified near Kearney. Even though soybeans can be produced profitably in SCN-infested fields, the nematode causes millions of dollars worth of soybean yield losses each year.
SCN causes no specific symptoms and its effects are often not dramatic. Thus, many farmers do not know that their fields are infested with SCN until severe problems develop. Meanwhile, up to 30% yield losses can occur without obvious symptoms.
Proper nematode management will consist of identifying infested fields and selecting nematode resistant varieties to plant in these fields.
Timing For Last Alfalfa Harvest Is Critical For Strong Spring Start
Reprinted from the August, 1994 Wardletter
While many alfalfa producers view the last cutting of the year as the end of another long growing season and a chance to stock up on winter feed, a longer term view should be considered as well.
Current research indicates the timing for the last cutting of alfalfa and other forage in the fall could have a dramatic impact on the start your crop gets the following spring according to Kearney, Nebraska soil scientist Dr. Ray Ward.
Dr. Ward says documented research indicates that alfalfa should enter winter dormancy with high levels of carbohydrates in the root reserves. To accomplish this, the last cutting should be complete four to five weeks before the average date for the first killing frost, defined as two consecutive days of 24 to 26 degree temperature.
Dr. Ward continued by saying that alfalfa, as a perennial plant, initiates regrowth after each cutting. The level of carbohydrates fluctuates with each cutting and during regrowth. Normally, a plant’s root system is fully “recharged” four to five weeks after harvest, even in the fall. As a consequence, harvesting four to five weeks prior to frost will allow ample time for the plant to grow and recharge in preparation for the winter dormancy.
During early growth after harvest an alfalfa plant uses up large amounts of carbohydrates from the tap root of the plant. After a plant reaches six to eight inches photosynthesis “kicks in” recharging the plant’s root system.
Studies indicate that up to 50% of the available carbohydrates are used to support the plant’s survival during the winter months. It is extremely important, Dr. Ward said, to allow enough time for regrowth before the first killing frost to fully recharge the root system with carbohydrates.
In short, careful timing on the part of a producer can insure good winter survival and rapid spring growth for next year’s alfalfa.
Nutrient Distribution In Plants Begins and Ends Near The Surface
To say that the distribution of plant nutrients is highest at or near the surface of the soil is generally true. To say that the surface is where the nutrients stay during the growing season is a whole different story.
As we analyze the table following this article, we clearly see a higher concentration of nutrients at 0-2” depth, then tends lower as deeper samples are analyzed. The table below is a soil analysis for a Hastings silt loam soil on our family farm that was limed two years ago at a rate of 1.6 tons/acre. Additionally all phosphorus and zinc has been broadcast on this field. In reality, producers could apply phosphorus and zinc in band below the surface with very little difference in the soil analysis as well. This field has been no tilled for 16 years.
The process after application is very simple. Plants take up the nutrients they need to grow from any sources available. In the fall, we usually harvest just the grain allowing the nutrient filled residue such as stalks, plant leaves and roots to fall to the ground. As the plant residue decomposes, nutrients in the residue return to the soil, normally at or just below the soil surface.
This natural process happens every growing season. It clearly explains why the nutrient values are highest near the soil surface.
Cover Crops Provide Benefits Today … and Tomorrow
Central plains producers are beginning to realize now what many producers worldwide have known for some time … cover crops are good and provide short and long term benefits.
Generally defined, cover crops are crops grown on land when you are not doing ordinary cropping. The concept of a crop growing to keep the ground covered can produce the following benefits:
The economics of cover crops in the Midwest are still being analyzed, but it is clear that their full value is clearly not understood. Many parts of the world use cover crops to build up organic matter and nitrogen in the soil. The practice of cover crops in the Midwest is just being studied now.
Dr. Ray Ward, President of Ward Laboratories, Inc. in Kearney is analyzing the use of cover crops on some of his fields in southeast Nebraska. Dr. Ward says that cover crops should be planted as inexpensively as possible. He is currently testing the use of turnips in a harvested wheat field. The turnips and volunteer wheat is grazed during the winter months and the field will be planted to corn next spring. He noted that he will have two years of data to report after this year. He already observed that his turnip cover crop corn field compared favorably to the corn field left to wheat stubble only.
Dr. Ward concluded by saying turnip is only one inexpensive crop cover to consider planting. Other inexpensive cover crops include mung beans, cowpeas, sun hemp, harry vetch, millet, sudan and rye.
Ward Laboratories Expands Forage Testing Capability
In a concerted effort to provide producers with the best possible information to help with production decisions, Ward Laboratories, Inc. will be adding the Relative Feed Quality (RFQ) test to their line up of forage testing procedures.
Beginning October 1, Ward Laboratories will run a combined forage analysis that will show the digestible Neutral Detergent Fiber (NDF), Relative Feed Value (RFV) and RFQ. Cost for the combined NIR analysis is $14 per sample.
“In short, we felt that RFQ is a better measure of the ability of the forage to perform. And, we are sure the information will be more useful to producers,” Dr. Ray Ward said. New developments and research make the RFQ a more valuable tool for producers to use, he added.
Simply stated, RFQ is a better gauge of the digestibility of alfalfa and grasses. Better digestibility, Dr. Ward says, leads to increased milk and beef production.
RFQ is calculated from knowledge of NDF digestibility and is a true measure of Dry Matter Intake (DMI). If the digestibility of forage is higher than average, a cow can increase its DMI. Milk production is partially determined by forage intake with the simple premise that the more a cow eats, the more milk she produces.
RFQ also measures the total energy consumed by the animal including not only fiber but non fiber carbohydrates as well. All of those compounds have an energy value that is not considered with the RFV test and are useful in determining overall forage quality.
NDF is an important component in determining the quality of forage. As a result, listed below are some factors that impact NDF digestibility.