Evaluation of Mosaic MicroEssentials Sulfur Fertilizer Products for Corn Production

Evaluation of Mosaic MicroEssentials Sulfur Fertilizer Products for Corn Production 2009 Preliminary Research Report Dr. John Sawyer and Daniel Barker Professor and Assistant Scientist Department of Agronomy Iowa State University Introduction Previously conducted research had indicated few crop responses to sulfur (S) fertilizer application across major soil areas of Iowa (Sawyer and Barker, 2002; Sawyer et al., 2009). Recent research in northeast Iowa has documented S deficiency in alfalfa and yield increases to S application on specific areas within fields (lower organic matter, sideslope landscape position, silt loam and loam textured soils) (Lang et al., 2006). On similar soils (and coarse textured soils) in northeast Iowa where early corn growth was exhibiting strong visual S deficiencies, research has documented growth response and yield increase to S application. That research indicates S containing fertilizer products are becoming more important for crop production in that geographic area of Iowa. In conjunction with phosphorus (P) application needs when soils are deficient in available P (Sawyer et al., 2008) or P applications are made to replace harvested nutrients, coapplication of S with a P fertilizer product would enhance efficiency and consistency of the nutrient applications by meeting both fertilization requirements. The objective of this study was to evaluate the Mosaic 12-40-0-10S (MicroEssentials MES10) product [comprised of monoammonium phosphate (MAP) plus ammonium sulfate (AMS) and elemental S in equal proportions] as an S and P fertilizer source for corn production. A second objective was to provide additional data on the potential for corn response to S fertilization in Iowa. In addition to the planned objectives, a second MicroEssentials product (MESZ 12-40-0-10S-1Zn) was evaluated as a zinc (Zn) fertilizer source. Data from that product was analyzed separately from the MES10 evaluation. Materials and Methods Two sites were chosen that had potential for soil S deficiency. One site was no-till corn following soybean (several years of no-till) at the North Iowa Area Community College (NIACC), Mason City, IA on a Readlyn loam soil. This location has the same soil and crop management practices as the site used in 2008 where early S deficiency symptoms were observed on corn plants. The other site in 2009 was at a production field near Madrid, IA on Nicollet and Clarion loam soils with corn following soybean. The Madrid site was located on a sideslope landscape position with indications of previous soi erosion in that area of the field. The field was spring tilled before planting. Fertilizer treatments were broadcast applied in the spring, prior to planting at the Mason City site and at corn emergence at the Madrid site. At the Mason City site, the cooperator did not apply any fertilizer to the study area. At the Madrid site, the cooperator had

2 applied N (anhydrous ammonia) at 140 lb N/acre spring preplant and 180 lb K 2 O/acre spring preplant and incorporated prior to planting. The following S and P treatment combinations were used at both locations (Table 1). The exceptions were that the N rate applied to equalize N at the Madrid site was 50 lb N/acre (N applied in addition to the 140 lb N/acre applied by the cooperator) instead of the 150 lb N/acre rate normally used and no K fertilizer was applied with the plot treatments since the cooperator had applied 180 lb K 2 O/acre across the field. 1. S-CON: S control, zero S (equalize N to corn need for the rotation; add P at the highest MES product rate) 2. MES-10: 10 lb S/acre from MES product (equalize N; equalize P to highest P rate) 3. AMS-10: 10 lb S/acre from AMS (equalize N; equalize P to highest P rate) 4. SP-CON: S&P control, zero P and zero S (equalize N) 5. MES-30: 30 lb S/acre from MES product (equalize N; no additional P as this is the highest P rate) 6. AMS-30: 30 lb S/acre from AMS (equalize N; equalize P to highest P rate) 7. MAP-30: P rate used in the MES 30 lb S/acre rate applied from MAP (equalize N; apply AMS at highest S rate) This set of treatments allowed the following planned S and P application comparisons: MES vs. S&P control [5 vs. 4]; S control vs. S&P control [1 vs. 4]; MES vs. MAP [5 vs. 7]; MES vs. AMS [2&5 vs. 3&6]; S control vs. 10 lb S/acre (as AMS) [1 vs. 3]; and 10 lb S/acre vs. 30 lb S/acre (as AMS) [3 vs. 6]. An eighth treatment (MESZ-30) was the MESZ product applied at a rate to supply 30 lb S/acre, which also supplied 3 lb Zn/acre. The product rates were set by the rate of S application. Those rates were 10 and 30 lb S/acre. The P application rate was set by the highest rate of the Mosaic MES product (120 lb P 2 O 5 /acre). For correct comparisons, rates of P were equalized when required by the specific treatment with triple superphosphate. The P rate was constant at 120 lb P 2 O 5 /acre for all treatments except the S&P control where no S or P was applied. The N rate was constant at 150 lb N/acre (Mason City site) or 190 lb N/acre (Madrid site), with N added as ammonium nitrate as needed to equalize N. Potassium was applied at 60 lb K 2 O/acre as potassium chloride to all plots at the Mason City site, and no K was applied at the Madrid site since the cooperator had applied K to the field.. Treatments were arranged in a randomized complete block design with four replications at each site. Soil was collected in the spring prior to treatment application from the 0- to 6, 6- to 12, 12- to 24, and 24- to 36-inch depths in each replication. The soil samples were analyzed for extractable sulfate at all depths. Samples from the 0- to 6-inch depth will be analyzed for routine soil tests (ph, P, K, Zn, and organic matter). Due to a miscommunication with the lab, these soil samples were discarded before all analyses were completed. The sites will be re-sampled in the spring 2010 in order to obtain these routine test results. The 2009 report will be updated once those soil test results are

3 available. Ear leaf samples (10 leaves per plot) were collected at the R1 (silking) corn growth stage from all plots and analyzed for total S, total P, and total Zn concentration. Corn canopy normalized difference vegetative index (NDVI) and chlorophyll index (Chl) was determined at the V10 growth stage with a Crop Circle ACS-210 (Holland Scientific, Lincoln NE) optical canopy sensor. The NDVI index relates to plant canopy biomass (NDVI) and the Chl index plant canopy chlorophyll. Grain yield was determined for each plot and reported at 15.5% moisture. Results and Discussion Mason City Site Soil test results available for the Mason City site are DTPA Zn at 1.2 ppm (0-6 inch depth) and the extractable soil sulfate-s at 4, 5, 5, and 4 ppm, respectively, for the 0-6, 6-12, 12-24, and 24-36 inch soil depths. These extractable sulfate-s results are low and at a consistent concentration with soil depth. The DTPA Zn test is in the Adequate range of the Iowa State University soil test interpretation for Zn (Sawyer et al., 2008). As mentioned earlier, soil test P for the site is not available at this time. Therefore, the soil test P interpretation for the site is not known or whether to expect a potential P response. There was a general increase in ear leaf S concentration with application of S fertilizer, either as AMS or MES10 products (Table 2). This is indicated by the across product mean leaf S concentration with applied S and the contrast of the MES-30 vs. the SP-CON treatment. However, the increase in leaf S concentrations with S application was small. Also, interpretation of corn ear leaf S concentration in regard to potential grain yield response is problematic as a wide range in critical concentrations have been reported in the literature and the relationship between leaf S concentration and yield response with recent research has been poor (Sawyer et al., 2009). The same general response was measured for ear leaf P concentration, with an increase in leaf P from 0.31% to 0.36% with the SP-CON vs. the S-CON treatments. These ear leaf S and P concentration increases indicate the crop availability of S and P from the fertilizer products, and a similar supply from each. However, the leaf P concentration without applied P is well above critical levels (Jones et al., 1990), therefore, expectation would be that corn yield would not be increased from P application. And that is what was measured (Table 2). The only contrast comparison that was significant was a lower yield for the MES-30 treatment. It is unknown why that product/rate would result in a reduced yield, and would not be expected due to either S or P application. Neither the lower MES-10 rate, nor the MAP-30 rate, resulted in a low yield. Interestingly, the canopy sensing indices (NDVI and Chl) had higher values for the S- CON compared to the SP-CON treatment, and for MES-30 vs. the SP-CON (Table 2). This indicates a response to the applied S and P in growth and greenness. With the treatment contrasts that are significant including the AMS-10 vs. AMS-30, the canopy response is from both S and P application. However, those measured responses did not translate to grain yield increase. Also, the increases in each index with S and P application were small. The canopy sensing also did not indicate any difference between

4 S or P fertilizer sources, nor did they give an indication of a lower yield with the MES-30 treatment. Madrid Site Soil test results available for the Madrid site are DTPA Zn at 0.8 ppm (0-6 inch depth) and the extractable soil sulfate-s at 4, 2, 2, and 3 ppm, respectively, for the 0-6, 6-12, 12-24, and 24-36 inch soil depths. These extractable sulfate-s concentrations are quite low across the soil depth sampled, and approximately half the 3-foot profile sulfate than at the Mason City site. This is likely a reflection of the soil differences between sites, such as organic matter, landscape position, and A horizon depth/erosion. The DTPA Zn test result is at the concentration break between the Marginal and Adequate ranges of the Iowa State University soil test interpretation for Zn (Sawyer et al., 2008). As mentioned earlier, soil test P for the site is not available at this time. Therefore, the soil test P interpretation for the site is not known or whether to expect a potential P response. The ear leaf S concentration increased with S application, however, the increase was greatest and only significant with the higher 30 lb S/acre rate (Table 3). The leaf S concentration with no S applied was the same as at the Mason City site, but the increase with the 30 lb S/acre rate was greater at the Madrid site. Both S fertilizer products resulted in the same increase in leaf S concentration, indicating equivalent crop available S supply. P concentration was increased with P application (significant S-CON vs. SP-CON contrast), and the concentrations were the same with all P fertilizer products and rates (Table 3). The leaf P concentrations were lower than at the Mason City site, but above ear leaf critical concentrations. As with the Mason City site, this would indicate an expectation that corn yield would not be increased from P application. However, there was a yield increase with P application, as indicated by the significant contrast between the S-CON and SP-CON treatments, and the lack of response to S application from any product (Table 3). However, the yields with the highest rate of P from the MES and MAP products were the same as the SP-CON. It is unknown why those treatments did not have higher yield as did other P applications. Otherwise, yields were the same for the P fertilizer products, indicating similar crop available P supply. The canopy sensing indices had inconsistent results (Table 3). The canopy NDVI was greater with the MES-30 vs. the SP-CON treatment, with the S-CON vs. the SP-CON, and with the MES-30 vs. the MAP-30. All differences were small however. The canopy Chl index was greater only for the MES-30 compared to the MAP-30. No other treatment differences were found for either canopy index. As with the Mason City site, differences in canopy index values did not translate to yield differences. Across Sites When analyzed across sites, there was a consistent response where the leaf S, leaf P, canopy indices, and grain yield were higher for the S-CON compared to the SP-CON. This indicates a response to applied P. Also, for all measurements except grain yield, values for the MES-30 treatment were greater than the SP-CON, again indicating response to applied P. However, the difference in grain yield for that comparison was not significant. For some reason, and as noted for each site, the grain yield was

5 comparatively low for the MES-30 rate treatment. This result also caused the yield comparison of MES and AMS to be significant, with an average lower yield with the MES product than AMS (where triple superphosphate was applied to equalize P). It is not known why this difference occurred. It does not appear to be due to P availability as the leaf P was increased the MES product application. Also, the effect from the higher MES- 30 rate is similar to the MAP-30 rate, and no yield reduction occurred with the lower MES-10 rate. These results may indicate an issue with the high P rate, and an issue with the MES and MAP products at that rate. That, however, did not occur for treatments where triple superphosphate was applied to balance the P application, such as both AMS S rates and the S-CON. Applying the higher AMS rate resulted in a small increase in leaf S concentration and canopy NDVI and Chl, but no difference in grain yield. Evaluation of MESZ Comparative results for the MESZ product (MESZ-30 rate treatment) were contrasted with the S-CON, MES-30, and AMS-30 rate treatments. This allowed evaluation of the MESZ product as a Zn source, as well as an S and P source. Results are given in Table 5 for each site and combined across sites. At the Mason City site, all products had similar leaf S, P, and Zn concentrations, and the same as the S-CON. The leaf Zn concentrations were low, and below the 15 ppm critical concentration (Jones et al., 1990). Application of Zn in the MESZ product did not increase leaf Zn. The canopy indices were greater for all products than the S-CON, indicating an S response. The grain yields were variable, with the AMS and MESZ having the same and highest yield, with the MES-30 yield the same as the control. This is the same result with the MES-30 rate as noted in the S and P product comparison. At the Madrid site, the MES and AMS products increased the leaf S concentration but the MESZ did not. The leaf P and Zn concentrations or canopy indices were not different than the control for any product treatment. The leaf Zn concentrations were higher than at the Mason City site, and above the 15 ppm critical level. Grain yield was significantly lower for the MES product, as noted before. The soil test Zn was near to within the Adequate interpretation range (Adequate at the Mason City site and at the break between Marginal and Adequate at the Madrid site). Based on those test levels, a yield response from Zn application would be small or more likely not expected. When analyzed across sites, the MES, MESZ, and AMS products applied at 30 lb S/acre resulted in a small leaf S concentration increase, no difference in leaf P or Zn concentration, some small but inconsistent differences in canopy NDVI and Chl (generally higher than the S-CON, but not for all treatments), and the same yields as the S-CON except for the MES-30 treatment which was lower than the control and the other product applications. As stated before, it is unknown why the MES product when applied at 30 lb S/acre had a lower yield. Summary These results indicate some S plant uptake response to applied S from all S fertilizer products (similar response from each product), but no yield response to S application at either site in 2009. There was P plant uptake response to all P fertilizer products, and a yield increase to applied P at the Madrid site and when analyzed across sites. The yield increase from P application was present for each product, however, for an unknown

6 reason the yield with the MES product when applied at the 30 lb S/acre rate resulted in no yield response at both sites compared to the control. This also occurred for the MAP product at the Madrid site. The products were surface applied at both sites, with one difference being the Madrid site was tilled and the Mason City site no-tillage. However, other P and S product applications (either different product or lower rate of MES) did not result in low yield and all of those combinations had yield increase from P application. Based on the results in 2009, no real difference was noted between S or P fertilizer products. There was no yield increase with application of Zn as MESZ. The MESZ product also appeared to supply equivalent S and P compared to the AMS and MES products. The MESZ product did not have the yield issue as noted with the high rate of MES. This lends further evidence that the lower yield with the MES-30 and MAP-30 treatments was due to something besides product application, although that is unconfirmed. References Jones, J.B. Jr., H.V. Eck, and R. Voss. 1990. Plant analysis as an aid in fertilizing corn and grain sorghum. p. 521-547. In R.L. Westerman (ed.) Soil testing and plant analysis. SSSA, Madison, WI. Lang, B., J. Sawyer, and S. Barnhart. 2006. Dealing with sulfur deficiency in NE Iowa alfalfa production. p. 213-222. In Proc. 18th Annual Integrated Crop Manag. Conf. 29-30 Nov. 2006. Iowa State Univ., Ames. Sawyer, J.E., and D.W. Barker. 2002. Sulfur application to corn and soybean crops in Iowa. p. 13-24. In Proc. 14 th Annual Integrated Crop Manag. Conf. 4-5 Dec. 2002. Iowa State Univ., Ames, IA. Sawyer, J.E., B. Lang, D.W. Barker, and G. Cummins. 2009. Dealing with sulfur deficiency in crop production: the Iowa experience. p. 64-73. In Proc. Thirty-Ninth North Central Extension-Industry Soil Fertility Conf., Des Moines, IA. 18-19 Nov. 2009. Vol. 25. International Plant Nutrition Inst., Brookings, SD. Sawyer, J.E., A.P. Mallarino, R. Killorn, and S.K. Barnhart. 2008. A general guide for crop nutrient and limestone recommendations in Iowa. pm 1688. Iowa State Univ. Extension, Ames, IA.

7 Table 1. Combination of fertilizer products and rates of S and P. Fertilizer Product Treatment S Rate P Rate 12-40-0-10S 21-0-0-24S 34-0-0 0-46-0 11-52-0 lb S/acre lb P 2 O 5 /acre - - - - - - lb product/acre - - - - - - 1 2 3 4 5 6 S Control (S-CON) Mosaic MES (MES-10) (NH 4 ) 2 SO 4 (AMS-10) S&P Control (SP-CON) Mosaic MES (MES-30) (NH 4 ) 2 SO 4 (AMS-30) 0 120 0 0 441 261 0 10 120 100 0 406 174 0 10 120 0 42 415 261 0 0 0 0 0 441 0 0 30 120 300 0 335 0 0 30 120 0 125 364 261 0 7 MAP (MAP-30) 30 120 0 125 289 0 231 12-40-0-10S, Mosaic MES10; 21-0-0-24S, ammonium sulfate; 34-0-0, ammonium nitrate; 0-46-0, triple superphosphate; 11-52-0; monoammonium phosphate. The N application was equalized on all plots at 150 lb N/acre (at the Madrid site 50 lb N/acre was applied to equalize N rates, with that N in addition to 140 lb N/acre applied by the cooperator). Potassium was applied as 0-0-60, potassium chloride, at 60 lb K 2 O/acre to all plots at the Mason City site, but no K was applied with the fertilizer treatments at the Madrid site as the cooperator had applied 180 lb K 2 O/acre.

8 Table 2. Effect of S and P product applications on ear leaf S and P concentration, corn canopy index values, and grain yield at the Mason City site, 2009. Treatment Tissue S Tissue P NDVI Chl Grain Yield % % bu/acre 1 S-CON 0.16 0.36 0.728 5.34 223 2 MES-10 0.18 0.36 0.738 5.61 235 3 AMS-10 0.16 0.36 0.735 5.54 231 4 SP-CON 0.14 0.31 0.718 5.09 222 5 MES-30 0.17 0.36 0.738 5.64 216 6 AMS-30 0.16 0.34 0.744 5.82 232 7 MAP-30 0.15 0.34 0.735 5.55 232 Treatment Contrast Statistics (p>f) MES-30 vs. SP-CON 0.001 0.017 <0.001 0.001 0.336 S-CON vs. SP-CON 0.018 0.014 0.042 0.065 0.814 MES-30 vs. MAP-30 0.018 0.298 0.554 0.515 0.014 MES-10 & MES-30 vs. AMS-10 & AMS-30 0.185 0.403 0.594 0.550 0.156 S-CON vs. AMS-10 1.000 0.939 0.142 0.141 0.199 AMS-10 vs. AMS-30 1.000 0.396 0.058 0.050 0.805 Indicates statistical significance of the contrast at p 0.10.

9 Table 3. Effect of S and P product applications on ear leaf S and P concentration, corn canopy index values, and grain yield at the Madrid site, 2009. Treatment Tissue S Tissue P NDVI Chl Grain Yield % % bu/acre 1 S-CON 0.16 0.30 0.742 5.75 255 2 MES-10 0.17 0.30 0.744 5.80 254 3 AMS-10 0.16 0.28 0.742 5.74 251 4 SP-CON 0.14 0.26 0.735 5.55 225 5 MES-30 0.18 0.29 0.742 5.75 233 6 AMS-30 0.19 0.30 0.744 5.81 255 7 MAP-30 0.18 0.30 0.734 5.50 226 Treatment Contrast Statistics (p>f) MES-30 vs. SP-CON 0.001 0.129 0.098 0.103 0.387 S-CON vs. SP-CON 0.167 0.023 0.098 0.103 0.004 MES-30 vs. MAP-30 0.572 0.317 0.047 0.046 0.439 MES-10 & MES-30 vs. AMS-10 & AMS-30 0.841 0.720 0.964 1.000 0.175 S-CON vs. AMS-10 1.000 0.132 1.000 0.931 0.611 AMS-10 vs. AMS-30 0.001 0.152 0.612 0.537 0.610 Indicates statistical significance of the contrast at p 0.10.

10 Table 4. Effect of S and P product applications on ear leaf S and P concentration, corn canopy index values, and grain yield across sites, 2009. Treatment Tissue S Tissue P NDVI Chl Grain Yield % % bu/acre 1 S-CON 0.16 0.33 0.735 5.55 239 2 MES-10 0.16 0.33 0.741 5.70 244 3 AMS-10 0.16 0.32 0.738 5.64 241 4 SP-CON 0.14 0.29 0.726 5.32 224 5 MES-30 0.17 0.32 0.740 5.69 225 6 AMS-30 0.17 0.32 0.744 5.81 244 7 MAP-30 0.17 0.32 0.734 5.53 229 Treatment Contrast Statistics (p>f) MES-30 vs. SP-CON <0.001 0.007 <0.001 <0.001 0.842 S-CON vs. SP-CON 0.016 0.001 0.014 0.020 0.014 MES-30 vs. MAP-30 0.255 0.958 0.101 0.084 0.503 MES-10 & MES-30 vs. AMS-10 & AMS-30 0.500 0.413 0.668 0.676 0.081 S-CON vs. AMS-10 1.000 0.279 0.292 0.317 0.817 AMS-10 vs. AMS-30 0.010 0.696 0.094 0.073 0.619 Indicates statistical significance of the contrast at p 0.10.

11 Table 5. Evaluation of MESZ fertilizer, 2009. Treatment Mason City Tissue S Tissue P Tissue Zn NDVI Chl Grain Yield % % ppm bu/acre 1 S-CON 0.16a 0.36a 12a 0.728b 5.34b 223bc 5 MES-30 0.17a 0.36a 11a 0.738a 5.64a 216c 6 AMS-30 0.16a 0.34a 10a 0.744a 5.82a 232ba 8 MESZ-30 0.16a 0.34a 11a 0.737a 5.62a 237a Madrid 1 S-CON 0.16b 0.30a 19a 0.742a 5.75a 255a 5 MES-30 0.18a 0.29a 19a 0.742a 5.75a 233b 6 AMS-30 0.19a 0.30a 20a 0.744a 5.81a 255a 8 MESZ-30 0.17b 0.28a 20a 0.739a 5.67a 250a Across Sites 1 S-CON 0.16b 0.33a 15a 0.735b 5.55b 239a 5 MES-30 0.17a 0.32a 15a 0.740ab 5.69ab 225b 6 AMS-30 0.17a 0.32a 15a 0.744a 5.81a 244a 8 MESZ-30 0.16b 0.31a 15a 0.738b 5.64b 244a Means followed by a different letter in a column within the same site or across sites are statistically different at p 0.10.