Effect of Potash Fertility on Orchardgrass Yield: 2023 Research Update
Andrew Kness and Erika Crowl
Orchardgrass is a popular pasture and hay forage species and it requires relatively high fertility levels, especially in a hay system where nutrients are being exported from the field. To test and demonstrate the importance of potash (potassium) fertility in orchargrass plantings, we established a replicated trial at the Western Maryland Research and Education Center. Three orchardgrass varieties were planted in a prepared seedbed at a seeding rate of 22 lbs pure live seed per acre using a drop-seeder on September 27, 2021. Plots were 6 feet wide by 20 feet long. Each variety received three fertility treatments: 1.) 0 lbs/A potash, 2.) 45 lbs/A potash (based on soil test), or 3.) 200 lbs/A potash, based on the potassium removal rate of 4 ton/A orchardgrass yield.
Three cuttings were taken from the trial in 2022; after each cutting, 50 lbs/A nitrogen was top dressed to all plots, as well as 50 lbs/A at green up. Potash (0-0-62) was top dressed on select plots after each cutting to reach 200 lb/A on the 200 lb/A plots and a single 45 lb/A application was made after first cutting on the plots receiving 45 lb/A potash.
Yield data was compiled and analyzed in JMP statistical software package, differences were separated using Fisher’s Least Significant Difference (α=0.10).
Interestingly in 2023, Potomac, an old variety, yielded significantly more (3.96 tons/A) than Olathe (3.65 tons/A) and Rushmore II (3.67 tons/A). In terms of fertility, plots that received 200 lbs/A potash yielded significantly more than those that received 0 and 45 lbs/A (Table 1).
Drier weather prevailed in 2023, preventing us from getting a third cutting. Methods remained the same as in 2022 with the exception of the fourth fertilizer application which was skipped due to the drought. As a result, all plots received 150 lbs/A total nitrogen and plots received between 45 and 120 lbs of potash/A depending on the treatment.
Overall, yields we lower in 2023 compared to 2022 as expected due to the reduction in fertility and rainfall. The top-yielding treatment was again the 200 lbs/A potash program with 2.57 tons/A, significantly greater than 0 and 45 lbs/A potash programs (p=0.003). While the 200 lbs/A potash plots only received 120 total pounds in 2023, this data demonstrates the importance of maintaining high potash fertility because these higher-fertility plots were able to cope with the drought stress better than those in the 45 and 0 lbs/A plots.
We will continue to collect yield data in 2024 and additionally collect new soil fertility data from the plots, as well as monitor disease presence and prevalence, as well as orchardgrass persistence.
We would like to acknowledge the Maryland Agriculture Experiment Station and the farm crew at the Western Maryland Research and Education Center for making this research project possible, as well as monetary support from the Maryland Horse Industry Board and USDA.
2022's Article on Effect of Potash Fertility on Orchardgrass Yield