Project Details:

Treatment Variable and Levels of Each. This study will take place on-farm at the Grett Dairy. Plots will be 32 feet wide and 1200 feet long, so that commercial equipment can be used for all operations. There will be three replications; treatments will be 0, 40, 80 and 180 lb K₂O/acre for alfalfa; and the design will be a randomized complete block. The potassium will be broadcast applied as KCl (60-0-0) in the fall.

Soil Characteristics. Along the rivers in the Tri-River Area, soils tend to be deep, nearly level, fine to medium-textured, somewhat poorly drained soils on alluvial fans, flood plains and low terraces. Mesas, high terraces, and old alluvial fans tend to have deep, nearly level and gently sloping soils with moderately fine texture. Many soils are derived from Mancos Shale which is naturally high in salt. Therefore, poor drainage is frequently coupled with high salinity. However, in this study, the highest yielding areas will be chosen for study, and the saline areas will be avoided.

Soil will be sampled and analyzed for NO₃-N, P, K, Ca, Mg, pH, OM, and EC, and P fertilizer will be applied according to soil test.

Cultural Practices. Cultural practices will be handled by the producer according to his usual practices. Fields in this area are typically furrow irrigated.

Alfalfa is commonly planted with oats as a companion crop, generally seeded at 10-15 lb/A. Some progressive growers seed alfalfa in late summer (mid-August to early September) as solo seeding at 15-17 lb/A following small grains. Generally, three cuttings are made per year, with a few producers getting four cuttings. County averages are in the 4 ton/A range, but good producers get 5.5-6.0 tons/A. Alfalfa varieties are numerous, and fertilizer applications generally include P depending on soil test and some N when newly seeded. Weed control (if any) is usually Velpar or Pursuit with occasional use of 2,4-DB. Insect control is primarily for alfalfa weevil and sometimes pea aphids mainly with Furadan. Stem nematode is a fairly common problem throughout the area, but rotation is about the only solution.

Parameters to be Measured.
Objective 1. Yield will be measured as green chop using a set of weigh pads. Alfalfa yield (total above ground dry matter) will be measured for each of three cuttings.

Objective 2. Soil samples (0-8 inch depth) will be taken prior to fertilization. Evaluations will be made regarding the accuracy of Colorado State University's potash recommendations based on soil test.