Maximizing wheat yields in North Dakota in a crop rotation system

An evaluation of the effect of crop rotations on wheat yield and quality.

IPNI-1982-USA-ND2

21 Jun 2001

Methodology

    The maximum wheat yield study will be conducted at the North Central Branch Experiment Station located at Minot, North Dakota with a crop rotation system including durum, sunflower and flax. Three separate one acre blocks of land (plus border or turn areas) in immediate proximity will be required to complete the rotation and grow each crop annually. Site selection will be determined and identified by soil survey personnel to insure uniformity of soil within the site selected. Initial chemical and physical properties of the soil will be determined to a depth of four feet at designated increments (0-3, 3-6, 6-12, 12-24, 24-36, and 36-48 inches.

    The experiment will be set up with three variable sin a split-split block arrangement with four replications. This arrangement will simply field management operations. The main plot variables include fungicide spraying (two), wheat varieties (two), and fertilizer management (three) which will apply to the wheat sequence of the study and not the sunflower or flax portion of rotation. The subunit plots will be either sixteen or twenty-four feet wide (8 or 12 foot drill) and thirty two feet long. This will consist of two drill widths of each wheat variety. One drill width will be reserved for harvest and one drill width will be used for destructive sampling (plant samples for evaluation of diseases and analysis of plant nutrients). The thirty two foot length will coincide with a sprayer boom that extends sixteen feet into the plot area so herbicides and fungicides can be sprayed from both sides to cover the plot subunit area without destruction of harvest or sample area. The experimental areas will be carefully marked so treatment variable son the wheat can be reimposed on the exact same area in the rotation sequence.

    The fungicide spraying variable will consist of a spray protection program or nonspray program each year on the plot area where wheat is grown. The fungicide spray program will be established by the Plant Pathology department using appropriate fungicides and spray sequences. This will consist of four sprayings at selected time or growth intervals from tillering stage to soft dough stage. The initial spray sequence will start after tillering is completed, followed with a spraying after 10 days (approximately boot stage). The third spraying will be at heading (prior to bloom) followed by a fourth spraying 10 days later at about late flowering. If a rain occurs within 24 hours after spraying, the plots will be resprayed. This sequence gives a spray protection program at about every 10-14 day intervals during critical periods of plant growth with reference to disease damage. Disease ratings will be taken at designated growth stages (early heading and milk stages). Since root rot disease cannot be controlled by spraying, the incidence of this disease will be evaluated across variety and fertilizer management systems with samples collected at flowering and at the soft dough stage for disease evaluations.

    Durum wheat will be grown for maximum yields with two variety studies. Disease resistance, maturity and yield performance will be the criteria used in selection of the varieties. One of the varieties selected will be early maturing and the other late maturing to enable evaluation of the climatic interaction with maturity as influenced by management since planting date is held constant. The variety within each maturity class should have maximum disease resistance and high yield performance as noted by variety trials.

    Three fertilizer management variables will be considered. The first treatment is a fertilizer recommendation (NP) for an average wheat yield goal (farmer expectation) of the area (35 bu/acre) based on the soil test son the wheat study area. The second treatment will be a fertilizer recommendation (NP) for a maximum wheat yield level expected for the area under ideal climatic and management conditions (70 bu/acre) based on the same soil test level from the first treatment. The third treatment wold be the same as the second treatment except will include a K fertilizer application (lb K/acre). Since starter fertilizer has been shown to be beneficial in wheat production and continues to be a standard practice it will be applied to all wheat plots at planting. Fifty pounds of 18-46-0 (dry) will be applied with the seed at planting. These three fertilizer management treatments will be applied to the plots only when wheat is grown. Since deep banding of fertilizer may prove beneficial, especially in dry years, all major application of NPK will be deep banded or subsurface applied. Major fertilizer applications of NPK will be applied as a solution using 28-0-0, 10-34-0 and dissolved KCl. The entire sunflower or flax plot sites in the rotation will be fertilized each year according to soil test levels from their respective first treatment area with a yield goal of 1800 lb/acre for sunflower and 20 bu/acre for flax.

    In the crop rotation system, all residues will remain over winter to maximize snow trap for replenishing the soil moisture reserves. The wheat will be planted no-till into standing fax straw. The wheat stubble will be plowed and seeded to sunflower in 30 inch spacing. The sunflower stalks will be disked and seeded to flax (two drill strips per plot). Maximum weed control will be maintained at all times on all crops using appropriate herbicides at recommended rates based on the weed species present. The sunflower crop will be cultivated. In planting each crop, special emphasis will be placed on population, thus all seeds will be uniformly screened for seed size and seeding rate adjusted for germination to insure uniform stands, especially between varieties. This step will be taken to insure that population differences are not introduced as a variable. Special emphasis will be placed on wheat seeding depth (should be 2 inches) to insure proper depth for adequate root rot ratings (second subcrown internode used as rating criteria).

    All plots will be harvested at maturity. The flax and wheat will be harvested with a small plot combine. Sunflowers will be hand harvested with heads removed, dried and threshed. Yields will be reported at 12.5, 10.0, and 10.0% moisture for wheat, flax and sunflowers, respectively, seed samples will be saved for analysis. Wheat yield will be used to evaluate the maximum yield trial while the flax and sunflower yields will be used to measure any difference sin residual moisture or fertility that occur and total production for the crop rotation system. Also, total dry matter (grain + stray or seed + stalks) on all crops will be saved for analysis. Nitrogen, phosphorus and potassium will be determined on grain and straw or seed and stalk samples collected. Seed weight and oil content will be measured on the grain and seed samples.

    Climatic data will be recorded and will include such measurements as air and soil temperature, relative humidity, wind, precipitation (growing and no-growing season), etc. Gravimetric soil moisture samples to a four foot depth will be collected annually in the spring and fall to determine crop water use. Soil samples will be collected to four feet to evaluate changes in soil nutrient levels. Additional data including initial and final stand counts, flowering dates, plant height and lodging will be recorded.