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Fluid Journal : Spring 2016
7 The Fluid Journal Spring 2016 No-till Corn Responds to Fluid Fluid Starters Response is significant in five of six experiments in Argentina. The Fluid Journal • Official Journal of the Fluid Fertilizer Foundation • Spring 2016 • Vol. 24, No. 2, Issue #92 Drs. Ricardo Melgar, Enrique Figueroa, Gabriel Kuriger and Diego Saba. Summary: There was significant response to starter fertilization in five of six experiments, as indicated by the contrast between the check and fertilized treatment. Fluid sources were not different to granular at the same rate and Phosphorus:Nitrogen (P:N) ratio. All evaluated grades were able to supply enough P or Sulfur (S) to achieve a reasonable replacement percentage (application vs. removal) but not for Potassium (K) in Mercedes, where the need for K in the starter is clearly demonstrated. ▼ DOWNLOAD Although the use of urea ammonium nitrate (UAN) and other N-S fluids has a wide and deep development in Argentina for many years, the availability of P sources, long awaited by fluid fertilizer users, may offer special and distinct challenges to all the value chain, from distributors to end users. Several local fertilizer firms are currently marketing P-based fluid fertilizers, either importing or manufacturing from imported phosphoric acid or solubilizing ammonium phosphates with sulfuric acid followed by neutralization. The application of NP or NPS/NPKS fluids as a starter has to have distinctive advantages over the solid granular blends via a rapid adoption from farmers, as well as lack of major disadvantages. Among the main concerns of farmers using starters--solid or fluid--is the effect of placement on toxicity to seeds, which has to do with the urea N and ammonium N amounts and the proximity of the fertilizer to the line of seeds. N and P are the same nutrients used in starters and considered the major contributors to grain yield, but also K and S are often included in starters, either solid or fluids. Since a corn crop yielding 10 Mg ha-1 would remove 38, 48, and 10 kg ha-1 of P, K, and S respectively, the challenge is to apply as much at sowing to cover replacement without waste and potential phytotoxicity. Objective The objective of this work is to find out the best NPKS grades and rates as a starter placed along the row of seeds at planting to maximize grain production in two regions of Argentina. We aim to get a simple blend proportion among common fluid sources that would be easily adopted by retailers and farmers. Methodology Site characterizations involved two field experiments that were carried out in the experimental stations of INTA Mercedes (Corrientes province, 29o11’S – 58o02’ W) and in a farmer field near Pergamino (Buenos Aires province, 33 o 56’S – 60 o 33’ W), during three consecutive seasons (2011-12, 2012-13, and 2013-14). Soils. The soil of the experiment at Pergamino is loamy clay, slightly acid Typic Argiudoll, with medium organic content, very well supplied with exchangeable K and cations, representative of Pampean soils used for grain crop production. On the other hand, the soil of the experimental site at Mercedes is a sandy loam Aquic Argiudoll, equally endowed with organic matter but much lower in available K. A composite soil sample was collected at both sites at planting to characterize the initial fertility of the site of the experiment, which is shown in Table 1 along with other agronomic characteristics of the crops for every season. Treatments. The experiment was a factorial of two rates and two grades of fluid fertilizer mixes plus a single rate of granular fertilizer blend and a check with N only (Tables 2 and 3). In Pergamino (Table 2), the fluid blend was an NPS one, made by mixing ammonium polyphosphate (APP, 11-37-0, sp. gravity 1.42 kg dm-3), urea ammonium nitrate (UAN,32-0 -0, sp. gravity 1.32 kg dm-3) and ammonium thiosulphate (ATS) 26-0 -0 -12S, sp. gravity 1.32 kg dm-3) with a 1:1 and 2:1 N:P ratio. The granular blend used Single super- phosphate (0-20-0 -125) and diammonium phosphate (18-46-0) to prepare a grade close to supply the same quantity and ratio of nutrients of the first fluid treatment. The experiment included a check without any fertilizer other than N, totaling seven treatments Plots. All plots received enough N as UAN between V6 and V8 stages to standardize all treatments in 160 kg ha-1 and thus compensating the N supplied at sowing by the different treatments. Conversely, the check treatment received