Identification of Management Practices and Cultivars for Organic Hard-Winter Wheat Production

Objective 1. Identify existing hard winter cultivars that perform best in yield, test weight, competitive ability, and disease and insect resistance or tolerance under organic conditions.

Across all four years, Bonneville was the top yielder without addition of compost and UT1944-158 (Golden Spike) was the top yielder with compost addition. Therefore, management of nutrients and non-nutrient effects will have a bearing on which cultivar should be selected under organic production. This genotype by environment interaction was not unexpected but does add another layer of complexity to management decisions. It should also be noted that while the difference between cultivars were statistically significant at alpha=0.05, a means separation test did not detect differences between the top nine cultivars. This was not expected but it is not surprising since only large differences would be detected with this experimental design which had the greatest power of detection of compost level differences and interactions between cultivars and compost level. The statistical analyses and means separations are included in the appendix.

Objective 2. Determine effectiveness and value of compost amendments and green manure in increasing yield and grain quality.
The nutrient and nonnutrient contributions of the compost application to grain yield were partitioned by solving the Mitscherlich equation for compost levels where applied nutrients were in surplus, calculating a nonnutrient Mitscherlich response equation, and solving the remainder as the nutrient contribution. The nonnutrient to nutrient yield response ratio varied from 0.25:1 for a year with larger amounts of precipitation to 2.2:1 during a dryer year. Contrary to results obtained from experiments where moisture is not a major limiting factor the nonnutrient effects of a compost application can be significant and even dominant. The lower yields in a dryland farming system require less nutrients, and nutrient requirements are met or exceeded by low rates of compost application. Higher rates of compost can still produce significant increases in yields due to nonnutrient effects. Furthermore, in areas where soil moisture is a significant limiting factor, the nonnutrient effects of even low rates of compost can be important, suggesting that increased infiltration and retention of moisture may be a significant nonnutrient benefit of compost in dryland systems. The study was not of sufficient length to continue to evaluate long term contributions to yield from the compost.

Objective 3. Determine the rate of mineralization and estimate number of years of benefit provided by compost addition.
Both the south and the north test plots showed significant nutrient and non-nutrient responses to the compost application. The overall yield increases for the maximum compost addition rate of 168 Mg ha-¹ averaged 250 percent. In contrast to most previously published experiments, the nonnutrient effects of the compost were significant and ranged from 25 percent of the nutrient effect to 225 percent of the nutrient effect. The nonnutrient benefit of the compost increased when water availability was more limited, and may have been due to increased water penetration and retention in the compost treated plots. This finding suggests that the relative benefits of a compost application in a dryland situation may change widely from season to season depending upon the availability of water.
The compost application resulted in a significant increase in soil available P levels. Approximately 10 percent of the total P contained in the compost was available for the crop within one year after application. By 1.5 years after application, a peak value of 20 percent of the total P in the compost was available. By the end of the experiment, three years after application, only 10 percent of the total P in the compost was still available. This reduction in P availability is typical for a calcareous soil. The rate of available P decrease declined 2.0 years after compost application. This decrease in P immobilization was probably due to the buffering effect caused by the production and dissolution of soil metastable calcium phosphate compounds.

The compost application resulted in significant increases in the availability of K, Zn, and Mn but not Fe or Cu. By one year after application, 90 to 100 percent of the total K contained in the compost was available as soil exchangeable K. This K remained within the top two feet of topsoil and was still available for plant use for at least three years after the compost application.

The soil availability of micronutrients supplied by the compost appeared to be controlled by organic complexing and inorganic precipitation reactions. Although the compost contained similar amounts of Zn, Mn, and larger amounts of Fe, the increase in soil DTPA extractable Mn was approximately 4 times the increase in extractable Zn levels, and no increase in extractable soil Fe levels was detected. The amount of Cu contained in the compost was too small to have a detectable effect on the soil.

Despite containing 2.2 kg Mg-¹ of total Na, having a pH of over 8.0, and having an H2O-extractable SAR of 18, the compost application did not cause an increase in soil Na levels even at the 168 Mg ha-¹ application rate. The compost included large amounts of Ca and Mg which were less immediately water soluble than the Na but were eventually released. This released Ca and Mg most likely competed with the released Na for cation exchange sites and prevented an increase of soil exchangeable Na levels. The SAR value of the compost was not a good indicator of the compost’s effect on the SAR of the soil. A ratio of the total Na to Ca plus Mg levels in the compost may be superior.

The compost application caused a significant increase in soil extractable P levels for several years after the application. After three years, soil extractable P levels were still elevated at a level equivalent to 10 percent of the total P applied. If the rate of extractable P decline from two to three years after application remains constant, this compost will probably provide a measurable residual effect for four to six years after the initial application.

The total K content of the compost provided a good estimate of the compost’s effect upon soil test K levels. The DTPA extract compost test provided a reasonable estimate of the increase in soil test Mn and Zn levels as long as an appropriate factor is included: two times the test level for Mn and 0.5 times the test level for Zn. It is unknown if these factors would be applicable for other compost applications in different soils. The DTPA extract compost test did not provide a good estimate for the effect of Fe in the compost upon the soil. Finally, because of the complex mineralization and precipitation reactions in the soil, no single compost test provided a consistent estimate of future soil P availability. The total P compost test may be useful for estimating peak levels of P availability, and the NaHCO3 compost test may be useful for predicting long-term P availability from the compost.

Compost applications show good promise in improving yields in dryland wheat farming systems. The addition of compost can have significant, beneficial non-nutrient effects as well as providing essential plant nutrients. The compost supplies available P, K, Mn, and Zn, and does so without causing a detrimental increase in soil Na levels.

Objective 4. Analyze the economic break even points through enterprise budgeting for organic production with and without compost addition.
Cost analysis assumptions & conclusions:

• Average yield for non-organic wheat was assumed to be 28.0 bushels per acre. Taken from 1996 Utah Agricultural Statistics (dryland, Box Elder county yields).
• Compost would be purchased and trucked 50 miles (one way).
• Compost charges are based on cost figures from E.A. Miller’s. If a return load is found, the mileage cost is reduced to $1.25 per mile.
• Land costs are not included in economic calculations.
• Labor costs are included in machinery operating costs.
• A $2.00 premium is given for the organic wheat (Richard Grover).

General Conclusions:

• Addition of compost is not profitable in the first crop year with any level of compost.
• The addition of 10 tons of compost per year becomes economically viable during the second crop year, if wheat is $3.50 (non-organic price) or higher.
• 25 tons of compost per year becomes economically viable during the second crop year, if wheat is $5.50/bu (non-organic price).
• 50 tons of compost per acre will take 3 to 5 crop years to break even (assuming yields remain constant).
• 75 tons of compost per acre takes 4 to 7 crop years to break even (assuming yields remain constant).

Objective 5. Determine end use quality of current cultivars and elite lines by mixograph, NIR and miller and baker evaluation.
Golden Spike will be released with General Mills as the licensee outside of Utah, but Utah growers will be able to grow the cultivar without a relationship to General Mills. This will allow organic growers the opportunity of using this cultivar. Collaborative quality tests have shown that this cultivar has excellent milling and baking quality and should be very attractive as an organic wheat since most organic wheat for bread is used as whole wheat flour and hard whites provide the most advantage to whole wheat four. Mills that evaluated Golden Spike for quality attributes were:

USDA-ARS Western Wheat quality Lab – Pullman, WA
Roman Meal Company – Tacoma, WA
Pendleton Flour Mills – Pendleton, OR
Cargill Flour Milling – Ogden, UT
Archer Daniels Midland Milling – Overland Park, KS
Fisher Mills Inc. – Seattle, WA
Wheat Marketing Center – Portland, OR
ConAgra Grain Processing Company – Omaha, NE
Nabisco Brands – Toledo, OH
Cereal Foods Processors – Ogden, UT
Krusteaz, Continental Mills – Seattle, WA

This extensive evaluation concluded that the bread making quality of this wheat was very good and the noodle color characteristics (controlled primarily by low levels of the enzyme polyphenol oxidase) were excellent. Hence this wheat may provide further value added for organic producers.