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Fluid Journal : Winter 2016
and the mineral nutrient of interest. In corn, the majority of nitrogen (N) and potassium (K) accumulation occurs before flowering compared to uptake of phosphorus (P), sulfur (S), and zinc (Zn), which primarily occurs during grain-filling (Bender et ai, 2013). Total requirements for some nutrients by soybeans (Bender et aI., 2015) are similar to those of corn, despite the misconception that nutrient management in soybeans is less critical because of N fixation as well as the notion that fertilizer supplied to a corn crop will also meet subsequent soybean fertility requirements. In soybeans, the majority of K accumulation occurs during vegetative and early reproductive growth, compared to the uptake of N, P, S, and micronutrients during seed-filling. Nutrient harvest index values (i.e., the portion of total nutrient uptake present in the grain) of N, P, S, are between 60 to 80 0 /0 for both corn and soybeans, which further necessitates adequate nutrient availability during seed filling. The unique partitioning of these nutrients to harvestable seed may partially explain the decreases in soil P, K, S, and Zn fertility levels reported by a recent IPNI summary (Fixen et aI., 2010). Achieving maximum yields while also sustaining the productivity of Illinois soils will likely require a comprehensive season-long fertility plan designed to meet the uptake needs of well-managed corn and soybean crops. Drip fertigation may become a component of the future agricultural landscape in Illinois and across the Corn Belt when coupled with efficient fertilizer placement, timing, and source technologies. The importance of supplying nutrients at key growth stages may be more vital for intensively managed corn and soybean production systems where other factors such as germplasm, pest control, plant density, and row spacing have been optimized. This research is designed to assess how fertigation might be used to increase corn and soybean productivity while also improving nutrient recovery efficiency Methodology Site characteristics. Experiments were conducted at the Crop Sciences Research and Education Center at Champaign, Illinois, using adjacent plots maintained in a corn-soybean rotation. Plots were planted on 15 June 2014. The site has been established by the University of Illinois Crop Physiology Laboratory as a long-term study site 11 - 2et4 g 0 illliJrTeIQI .. .. .. 311 Yr g DillliJrT BIll -2et4R ...-. -2et4R ...-. + hlgdion ( . - 2et4 R ...-. + hlgdion (Com] 100 60 ..... IL lID 50 D ..... ..... . C - ... 40 ..... ::J C 1iS 6D 0 ... - . 3D 1iS .... - 40 D- . - I- 20 u e :>.. - IL - 2D . 10 D o 0 150 170 190 210 23D 250 270 29D Julian Day Figure 1. Actual and 30 yr avgs for daily avg temp and cumulative precip & cumulative precip + irrigation measured at Champaign, IL during 2014. Water volume supplied for corn and soybean trials totaled 4.04 and 2.94 inches, respectively. Table 1. Effect of hybrid selection and fertigation treatment on corn grain yield at Champaign, IL during 2014. A total of 80 Ib N, 70 Ib K 2 0, and 14 Ib S on a per acre basis were applied during six fertigation periods between V6 and R2. Hybrid Irrigated Fertigated Difference ------------------------- Yi e I d (B U Ac- 1 ) ------------------------- DKC62-08 155 175 20* DKC63-33 180 202 22* N63R-3000GT 180 200 20* Average 172 192 20* (*) Significantly different than zero at a=0.1 O. Table 2. Effect of hybrid selection and fertigation treatment on R6 biomass for corn hybrids grown at Champaign, IL during 2014. A total of 80 Ib N, 70 Ib K20, and 14 Ib S on a per acre basis were applied during six fertigation periods between V6 and R2. Recovery efficiency represents the percentage of total applied nutrients accumulated in above-ground biomass. Hybrid Irrigated Fertigated Difference Recovery Efficiency (oÆ>) R6 Biomass (Ib Ac- 1 ) N K S DKC62-08 20911 22440 1529 53.6 58.9 21.3 DKC63-33 22134 23476 1342 44.8 37.1 17.0 N63R-3000GT 23762 25436 1674 37.7 53.6 16.5 LSD (a=0.1 0) 583 587 711 14.1 13.6 6.8 on a Drummer silty clay loam (fine silty mixed, super-active, mesic Typic Endoaquolls)- Flanagan silt loam (fine, smectitic, mesic, Aquic Argiudolls) soil. Site characteristics included 3.6 0 /0 organic matter, 21.1 meq/100g CEC, 5.8 pH, 22 ppm P, 99 ppm K, and 9.5 ppm S using Mehlich-3 extraction. Corn and soybean experiments were managed with herbicide and fungicide applications and were well-suited to provide evenly distributed soil fertility, pH, soil organic matter, and water availability. Commercially available corn and soybean The Fluid Journal Winter 2016