EFFECT OF AVAIL ON CORN PRODUCTION IN MINNESOTA

Transcription

1 EFFECT OF AVAIL ON CORN PRODUCTION IN MINNESOTA Gyles Randall and Jeff Vetsch 1/ Diammonium phosphate (DAP) and monoammonium phosphate (MAP) fertilizers that have been coated with a shield that surrounds the fertilizer granules are commonly referred to by the fertilizer name AVAIL. The purpose of this coating, which expands when applied to the soil, is to block the elements (Fe, Al, Ca, and Mg) in the soil that fix P. The goal is to provide enhanced nutrient availability making more of the fertilizer P available to the plants root systems all season long and the opportunity for higher yields and increased profit (Source The objective of this study was to evaluate the performance of AVAIL (coated DAP and MAP fertilizers) compared to conventional DAP and MAP on corn production in southern Minnesota. Experimental Procedures Experiments were conducted on fine-textured glacial till soils at the Southern Research and Outreach Center, Waseca, MN in 2002, 2003, and All experimental procedures are presented in Table 1. In 2002 and 2004, the experiments were located on calcareous Canisteo soils that had low levels of Olsen extractable P. The site in 2003 was located on a Webster soil, which is very closely associated with the Canisteo soils, but does not have a calcareous surface soil. Exchangeable K was high to very high each year; thus, fertilizer K was not applied. Recommended rates of N as urea were applied each year. In 2004, an additional 30 lb N/A as UAN was applied sidedress because of excessive late May and early June rainfall. The conventional and coated forms of DAP and MAP and the urea were broadcast applied in late April. The experimental site was field cultivated once on the same day to incorporate the treatments. Corn was planted at high populations within a couple of days. Excellent weed control, high populations, and adequate rainfall provided high-yield conditions where yield responses to fertilizer P were expected. The P treatments, including rates, sources, and method of application, varied each year. However, the granular AVAIL fertilizer (DAP in 2002 and 2003 and MAP in 2004) was provided by Specialty Fertilizer Products each year. In 2002, we mixed the appropriate amount of AVAIL product with the before applying in a 2 x 2 starter band. Results and Discussion Corn grain yields were increased over the zero-p control by about 17 bu/a with broadcast-applied DAP and about 37 bu/a with the AVAIL (coated DAP) in 2002 (Table 2). The 20 bu/a advantage for broadcast AVAIL compared to conventional DAP was considerably different compared to applying AVAIL with the 2 x 2 starter. When applied with 8 gal/a of , the treatments containing 2 or 4% AVAIL (coated DAP) reduced yields about 15 bu/a compared to without AVAIL. Thus, Broadcastapplied AVAIL produced corn yields about 30 bu/a greater than the 2 x 2 starterapplied AVAIL. At this time, we have no explanation for the poor performance of the starter treatments. Plant stands were not affected, and no visible indicators of phytotoxicity were observed. 1/ Soil Scientist and Professor and Assistant Scientist, respectively, Southern Research and Outreach Center, Univ. of Minnesota. Waseca, MN

2 Ten small whole plants were harvested from each plot at the V6 stage. The plants were dried, weighed for total dry matter (DM), ground, and analyzed for total P. Dry matter yields shown in Table 2 were greatest for the 25 and 50-lb P 2 O 5 AVAIL treatments and the 50-lb P 2 O 5 conventional DAP treatment. Early growth was not different between the zero-p control treatment and the 2 x 2 starter treatments. The P concentration and P uptake data were not statistically different among the treatments due to high variability (CVs from 16 to 26). In 2003, corn grain yields topped 200 bu/a, but a significant yield response to fertilizer P was not found (Table 3). Similarly, DM at V6 for the conventional DAP and AVAIL treatments was not statistically different from the zero-p control. This site, a Webster soil, was not calcareous (ph=6.4). The Olsen extractable P was 13 ppm (MH), and the soil was able to supply sufficient P for very high yields. The Canisteo soil at the experimental site in 2004 had the highest ph (7.8) and lowest Olsen P levels (4 ppm) of the three site-years. Thus, a 30 bu/a corn yield response was obtained for the 30, 40, and 50-lb P 2 O 5 treatments over the 0, 10, and 20-lb treatments for both conventional MAP and AVAIL (coated MAP). We were surprised at the consistent lack of yield response to the 10 and 20-lb P 2 O 5 broadcast treatments. The 4 bu/a difference between MAP and AVAIL (coated MAP) was not significantly different. There was no interaction between P 2 O 5 rate and P source (MAP vs. coated MAP). Whole plant DM at the V6 stage was not statistically different among treatments due to high variability. For some unknown reason, plant growth within rows and plots was quite variable. This was observed from about the V4 stage through the VT stage. Summary Significant corn yield responses to P were obtained in 2 out of 3 years. In the two responding years, broadcast-applied AVAIL (coated DAP) was superior to conventional DAP in one year (2002), but there was no difference between AVAIL (coated MAP) and conventional MAP in the other year (2004). Broadcast-applied AVAIL performed considerably better than 2 x 2 starter applied AVAIL in the only year we compared P placement. Plant growth at the V6 stage showed larger plants with the broadcast AVAIL treatments in one of the two years when a yield response to P was obtained. Early growth was not statistically different from the zero-p control in the other year due to high variability. Based on these data, the AVAIL products (coated ammoniated phosphates) appear to possess characteristics that allow greater P availability in calcareous soils and give higher corn yields in some cases. However, the inconsistency as noted by a 20 bu/a yield advantage for broadcast AVAIL (coated DAP) over conventional DAP in one year and no yield difference between AVAIL (coated MAP) and conventional MAP in another year is of concern. The poor performance of 2 x 2 starter-placed AVAIL with is also of concern. Our three site-year findings suggest that more trials be conducted in a very organized fashion to determine when and why the AVAIL products will out-perform conventional DAP and MAP most consistently and significantly.

3 Table 1. Experimental procedures used in the AVAIL studies at Waseca, MN in Year Parameter Soil type Canisteo cl Webster cl Canisteo cl Previous crop Soybean Corn Corn Replications Soil ph Olsen Ext. P (ppm) 6 (L) 13 (MH) 4 (L) Exch. K (ppm) 170 (VH) 261 (VH) 134 (H) Tillage Fall NT M. Plow M. Plow Tillage Spring field cult (5/1) field cult. (4/25) field cult. (4/24) N rate/(lb/a), source, & date of application 120, urea, 5/1 160, urea, 4/30 160, urea, 4/24 30, UAN, 6/22 Bdct. P application date 5/1 4/25 4/24 Planting date 5/3 4/26 4/28 Hybrid P37H27 P36B09 DKC Herbicides Surpass & Roundup Harness & Hornet Harness & Callisto Final stand (plants/a) 33,800 32,100 33,100 Harvest date 10/2 10/1 10/11

4 Table 2. Effect of broadcast and starter DAP and coated DAP (AVAIL) on corn grain yield and early growth at Waseca, MN in # Source P Rate P Management H 2 O Yield Yield [P] P Uptake lb P 2 O 5 /A % bu/a lb DM/A % lb P/A 1 None 0 None DAP 25 Bdct. Incorp DAP 50 Bdct. Incorp coated DAP 25 Bdct. Incorp coated DAP 50 Bdct. Incorp gal 2 x 2 starter % coated 8 gal 2 x 2 starter % coated 8 gal 2 x 2 starter P > F: LSD (0.10): NS NS C.V. (%): Table 3. Effect of rate of broadcast DAP and coated DAP (AVAIL) on corn grain yield and early growth at Waseca in # Source P Rate P Management H 2 O Yield Yield lb P 2 O 5 /A % bu/a lb DM/A 1 None 0 None DAP 25 Bdct. Incorp DAP 50 Bdct. Incorp coated DAP 25 Bdct. Incorp coated DAP 50 Bdct. Incorp P > F: LSD (0.10): NS NS NS C.V. (%):

5 Table 4. Effect of rate of broadcast MAP and coated MAP (AVAIL) on corn grain yield and early growth at Waseca in # Source P Rate H 2 O Yield Yield lb P 2 O 5 /A % bu/a lb DM/A 1 None MAP MAP MAP MAP MAP Coated MAP Coated MAP Coated MAP Coated MAP Coated MAP Stats for RCB Design (all treatments) P > F: LSD (0.10): NS 23.7 NS C.V. (%): Stats for RCB Design Factorial Arrangement (treatments 2-11) Phosphorus Rate (lb P 2 O 5 /A) P > F: LSD (0.10): NS 15.9 NS Source of P MAP Coated MAP (AVAIL) P > F: Interaction Rate x Source P > F: C.V. (%):