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Fluid Journal : Winter 2016
Variable Rate Starter Fertilization Does it affect corn yield and should it be based on soil attributes? Jeffrey Vetsch and Dr. Daniel Kais er The Fluid Journal · Official Journal of the Fluid Fertilizer Foundation · Winter 2016 · Vol. 24, No.1, Issue #91 T DOWN LOAD Summary: Some key observations. Plant populations were rarely affected by ferlilizer P treatments. Generally, broadcast and starler ferlilizer enhanced early growth of corn. Broadcast P applications increased yields at five of eight locations while starler applications increased yields at only two of eight locations. Our findings contradicted our experimental hypotheses that corn grain yield response would be affected by starter rate and starler rates should be varied based on soil attributes. S tarter fertilizers containing phosphorus (P) have been found to enhance early growth and yield of corn, especially on poorly drained soils of the northern Corn Belt (Randall and Hoeft, 1988, Vetsch and Randall, 2002). The largest yield responses to starter Pare often found where soil test P is less than optimum (Bermundez and Mallarino, 2004) and on P fixing soils (Rehm et al., 1988). Phosphorus fixation is usually associated with calcareous soils with pH values greater than 7.4. A significant proportion of soils in South Dakota, Minnesota, and Iowa, which developed from glacial deposits from Des Moines Lobe till, are P-fixing soils. The location and extent of P-fixing soils vary significantly by geographic region within these states and, more importantly, vary across the landscape within a given farm field. Identifying or mapping the extent of P-fixing soils in a given field can be aided by several soil attributes. Soil test P, pH, calcium carbonates (CaC03) and soil, topographic, and yield maps could all aid in identifying these areas in fields. Generally, grid soil samples, analyzed for pH and soil test P, are the first step toward identifying and mapping low P and potential P fixing areas of fields. On P-fixing soils a fluid starter fertilizer, such as ammonium polyphosphate 15 f ;;.6oi ..". "." -, 4 . t If ..... , L':;- r --.. \> --. -' l .J.. -\ . t '\ iI- . ... . '\ \ , ,,'t ..(, - .... fj".. \';. " "', '! ... : '" ... "'\ ..J: ... ...... . ..... ... (APP) applied in-furrow, may be an efficient and economic way to manage P compared with a traditional broadcast application, especially on farmland in short-term rental contracts where the farmer is not necessarily interested in building soil test levels. Instead, their primary goal is to maximize yield and profit while minimizing risk. Previous research has answered many questions on starter fertilizer sources, placement, and rates. However, widespread adoption of variable rate fertilization and availability of variable rate controllers has led to two new questions: 1) does the optimum rate of starter fertilizer vary enough within a field to require variable rates of starter? and 2) what soil attributes or landscape parameters can be used to make variable starter rate application recommendations? These questions will be addressed by measuring the response of corn to multiple rates of APP applied in-furrow to a field containing soil variability (pH, soil test P, etc.) typical of the region. The starter rates will be applied within blocks- -with and without broadcast P fertilizer. The with-and-without broadcast P blocks will allow us to compare the efficiency of starter P to broadcast P across the landscape. Objectives The Fluid Journal '"' . :\1 . .' - t ' : I · - _J t t ... t -- r -I .. \ ... . \. "" , .. 'Ii<' · i. ',.. ""':\ r. .- \ :"* - 4[ .; r; '"!" \: -.... "" --- Iiol . ,- \ ........ ,- ,. ., l ... \ ....... , '. . "- 1'00. The objectives of this study are: · To measure the effect of the rate of application of APP on early growth of corn, grain yield, P removal in grain and fertilizer use efficiency (FUE) · To determine if the optimum rate of APP varies within a field · To develop and calibrate an algorithm for making variable rate starter applications based on soil attri butes · To compare and contrast the effects of broadcast P addition on the response(s) observed in objectives 1,2,and3. Methodology Design. The field research study was performed using a modified strip trial design. This unique design uses traditional small plot methodology, which includes small plot equipment (planter and combine), experimental design, and appropriate statistical analysis. However, each two-three acre experiment was arranged like a traditional strip trial with strips running the length of the field. The primary difference was each strip was subdivided into 65-foot long segments with each treatment (rate of P fertilizer) randomly applied within each strip and replication using variable-rate controllers and GPS guidance. This design Winter 2016