During the 2014 growing season, several on-farm research studies were established in collaboration with Kim Larson, Kansas River Valley Extension District Agent, and soybean producers in that district. The experimental layout, field variability, and strip-trial position in the field for those studies are presented below.
An example of the experimental design proposed for the 2014 soybean seeding rate trials is presented below. In this example, five seeding rate levels were investigated with three replications (completely randomized) in all 15 soybean strips.
Strip-trial, soybean seeding rate:
Soybean seeding rate trial and position in the field:
Yield outcomes from a seeding rate study
In this example, five seeding rates were evaluated in a north central Kansas location. Agronomically, the optimum seeding rate and final plant population for this study was 80,000 plants per acre final stand count, which was equivalent to a seeding rate of 90,000 seeds per acre. Maximum soybean yield was about 60 bushels per acre, but there was quite a bit of variability around that 60-bushel average. The most consistent yield results were at the seeding rate of 120,000 per acre. In this specific site, increasing seeding rate over 90,000 seeds per acre did not promote an improvement in yields. Soybean productivity plateaued for the seeding rates 120, 150, and 180 thousand seeds per acre.
Similar soybean seeding rate studies were performed in collaboration with Extension agents and producers, resulting in diverse soybean yield responses to seeding rates.
This is just one study and one site. Thus, one should be careful in interpreting the results. The goal of this information is to motivate soybean producers to perform more on-farm research evaluations and to understand the complexity of our soybean farming systems. In addition to this, the on-farm data emphasizes the need for further site-specific, on-farm evaluations on the response of soybean yields to seeding rates and how management practices interact with the environment.
More information on the on-farm studies will be summarized in coming issues of the K-State Agronomy eUpdate. Stay tuned.
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
Guillermo R. Balboa, Graduate Student in Agronomy, Fulbright Scholar