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Fluid Journal : Spring 2011
7 The Fluid Journal Spring 2011 Summary: We designed and conducted a simple fertilizer response trial using an omission technique. We applied fertilizer to the research plots on April 14, 2008, a couple of days before the rest of the field was custom applied by Interior Seed and Fertilizer Ltd.'s floater applicator. We flagged the experimental site so it was fertilized when the rest of the field was fertilized. We took the forage yield samples off the research plots twice. The results clearly showed that there was a response to nitrogen (N). All other nutrients did not show as clear a response when compared to the complete blend or the no-fertilizer treatment. However, even though we were not able to show statistically the yield increasing effect of each of the other nutrients besides N, there was a slight yield decrease when each nutrient was omitted, compared to the complete blend, so each nutrient did contribute to a yield increase. Omission plot design employed to show farmer whether or not there is a yield increase response. Answering the question: does fertilizer applied give yield increase? The Fluid Journal • Ofﬁcial Journal of the Fluid Fertilizer Foundation • Spring 2011 • Vol. 19, No. 3, Issue #73 Dr. Tom Jensen Does the fertilizer you apply always give the result you expect? Farm customers want to know that the fertilizer they apply is resulting in a yield increase. Of all fertilized crops, it is my observation that we have more questions about whether or not the fertilizer works when it is applied to forage stands. I'm not certain why this is but perhaps it is because whether a forage crop is grown for grazing, hay, or silage, it is difficult to measure yield increases due to fertilizer when compared to grain crops, especially when the stand is grazed. Soil testing is often used as a first step in deciding which nutrients apply and at what rate of application for each nutrient. These recommendations are usually based on regional fertilizer response trials, targeting normal yields for the area. I can remember a little over ten years ago, while working as an agronomist out of Calgary, I received a phone call from the manager of Interior Seed Fertilizer Ltd. in Cranbrook, BC. He asked me to consider conducting a fertilizer response trial on an irrigated forage field of a ranch customer. Having the time and resources that spring to assist, I obliged. Assessing The ranch customer thought that fertilizer response was disappointing on fields used for a combination of hay and grazing. They usually fertilized in early spring, took the first cut as hay, and grazed the regrowth in late summer or early fall. The ranch owner said, "I just don't think the fertilizer you apply for us really results in much increase in forage growth. How can you show me that your fertilizer works?" In the past he had soil tested at least every few years. The soil test results taken the previous year (2007), on the field where the study was proposed, are shown in Table 1. The irrigated field was estimated at having a 25 percent alfalfa and 75 percent forage grass stand. The target forage yield was 3 tons/A. The fertilizer blend generated using the soil test results for the field in 2007 and used again in 2008 (the year of the fertilizer trial) was 230 lbs/A with a blend analysis of 17-13-17-6.5 sulfur (S). The actual nutrients applied totaled approximately 40 lbs N, 30 lbs phosphorus (P2O5), 40 lbs potassium (K2O), and 15 lbs S per acre. Omission plot. We designed and conducted a simple fertilizer trial using an omission technique. This is accomplished by having a plot where each one of the nutrients being evaluated is missed or omitted on a plot, while at all the other plots nutrients are applied. There is one plot that receives all the nutrients. If there is no decrease in yield when a nutrient is omitted, compared to an all-nutrient plot, it is assumed that there is a sufficient amount of that nutrient being supplied from the soil and there is no measurable additional response to that particular nutrient. We also employed a no-fertilizer or check plot. This is useful to determine whether or not there is any fertilizer response. We repeated each 6.5-ft by 13-ft plot four times, using a randomized block design so we could analyze the results statistically. We evaluated forage yield response to the following nutrients: N, P, K, S, and boron (B). The NPKS was applied at the per-
Early Spring 2011