Foliar Nitrogen Fertilization of Irrigated Maize University of Nebraska South Central Agricultural Laboratory

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1 Foliar Nitrogen Fertilization of Irrigated Maize University of Nebraska South Central Agricultural Laboratory Procedures The study was conducted primarily to evaluate the potential for foliar application of ureaammonium nitrate solution to irrigated maize, and the inclusion of N Boost with foliar N application, on grain yield and N use efficiency. The study was located at the University of Nebraska s South Central Agricultural Laboratory near Clay Center, Nebraska. The study was a randomized complete block design with four replications. Individual plot dimensions were 8 rows (6.1 m) wide by 15.2 m long. The site consisted primarily of one soil series Crete silt loam. The study was located on a linear sprinkler irrigated field (Figure 1). Initial soil sampling took place March 18, Soil samples (0 20 cm, cm, cm) were collected from each of the 4 reps across the study area by hand. Results of these analyses are in Table 1. Table 1. Initial soil test levels. Soil Test Mean Values Organic Matter (%) 3.6 ph 6.8 Mehlich P III (ppm) 12.0 K (ppm) 358 Zn (ppm) 0.61 S (ppm) 7.5 Mg (ppm) 310 Ca (ppm) 2482 CEC (meq/100) cm NO 3 N 3.03 ppm cm NO 3 N 2.13 ppm cm NO 3 N 1.65 ppm The prior year s crop was irrigated maize. Preplant nitrogen (N) treatments (28% UAN) were applied April 22, 2010 using an 8 row Capstan liquid N metering system. Maize (Pioneer 33P83) was ridgeplanted into shredded maize stalks May 6 at a population of 73,110 seeds ha 1. An 8 row planter was used (0.76 m rows). Alleys were tilled June 4 and plots were staked. Stand counts taken June 5 (maize at the V3 growth stage) found an average of 62,295 plants ha 1. Stands were reduced 15% due to wet

2 soil and heavy surface residue at planting. Early season plant growth was also irregular due to spring compaction from wet field conditions for shredding, fertilizing, and planting operations. Foliar UAN treatments were applied with a boom sprayer (193 liters ha 1 rate at 4.2 km h 1 TeeJet 8002 DG tips at 206 kpa, 0.5 m nozzle spacing). The first foliar N treatments were applied at the V4 growth stage on June 11. It was mostly cloudy; air temp. was 24º C, 10 cm soil temperature was 24º C, with an easterly wind at 16 km h 1 and 80% relative humidity. Foliar N treatments were again applied at the V9 growth stage on June 24 using the same sprayer. It was mostly sunny, air temperature was 24º C, 4 in. soil temperature was 23º C; with a southerly wind at 8 km h 1 and 60% relative humidity. Rainfall from April 1 through October 1 at the South Central Agricultural Laboratory totaled 546 mm (113% of normal). This was supplemented with 170 mm of irrigation in five events. At physiological maturity (black layer) Sept. 16, whole plants were harvested from the plots, outside the harvest areas, for total dry matter weight and total N analysis. Two rows of each plot were harvested October 8 with a Gleaner plot combine. Grain samples were retained for total N analysis, allowing for estimation of harvested nutrient removal. Figure 1. Aerial image of foliar N study, 16 July Study area outlined with light green boundary. Soil series designations are: Ce = Crete silt loam, 0 1% slope; Cg = Crete silt loam, thick solum, 0 1% slope; Bu = Butler silt loam, 0 1% slope. Foliar N Fertilization Study 2010 University of Nebraska South Central Ag Lab Page 2

3 Treatments: Preplant N Foliar N Foliar UAN Foliar NBoost Total N No. kg ha 1 Source (kg N ha V4&V9) (l ha 1 ) (kg ha 1 ) UAN +NBoost UAN +NBoost UAN +NBoost UAN +NBoost UAN +NBoost UAN +NBoost UAN +NBoost Results Overall treatment results are summarized in Table 2 and 3. There were generally significant effects of preplant N rate on all parameters of interest other than plant population. Foliar N application significantly increased grain yield and grain N uptake. The use of N Boost significantly increased grain yield and grain N uptake. There was a trend for increased fertilizer N recovery with the use of N Boost. Figure 2 illustrates the trend in grain yield as influenced by combinations of preplant and foliar N, and the addition of N Boost to foliar N application. Table 2. Analysis of variance. Cells with NS are not statistically significant at PR=0.05. Pr>F Stover N Grain N Total N Fertilizer N Recovery Population Stover Yield Grain Yield Factor (plants ha 1 ) (kg ha 1 ) (kg N ha 1 ) (kg ha 1 ) (kg N ha 1 ) (kg N ha 1 ) (fraction) Rep < NS NS NS NS Preplant N (PPN) NS < < < < < Foliar N (FN) NS NS NS NS NS NBoost (NB) NS NS NS NS PPN*FN NS NS NS NS NS NS NS FN*NB NS NS NS NS NS NS NS PPN*FN*NB NS NS NS NS NS NS NS Mean CV (%) Foliar N Fertilization Study 2010 University of Nebraska South Central Ag Lab Page 3

4 Table 3. Treatment means. Means with the same letter are not statistically significant at PR=0.05 according to Duncan s Multiple Range Test. Mean Values Stover N Grain N Total N Fertilizer N Recovery Population Stover Yield Grain Yield Treatment (plants ha 1 ) (kg ha 1 ) (kg N ha 1 ) (kg ha 1 ) (kg N ha 1 ) (kg N ha 1 ) (fraction) b 9548 d 56.0 c 5783 g 67.1 f f b c 68.7 bc 6904 fg 79.1 ef ef 0.16 d ab bc a 8465 e 95.9 de bcd 0.47 ab ab ab a abc ab ab 0.58 ab b ab a abc ab ab 0.51 ab ab c 72.0 bc 8235 ef 94.6 de def 0.23 cd ab bc 89.4 abc 8838 de cd cde 0.37 bcd ab bc 92.2 ab cd bc bcd 0.40 abc ab ab a bc ab abc 0.50 ab a a a abc ab a 0.54 ab b ab a a a a 0.57 ab ab ab a ab a a 0.63 a Grain Yield (kg ha -1 ) N Boost Preplant Nitrogen (kg ha -1 ) Figure 2. Treatment effect on grain yield with combinations of preplant N only, preplant N + foliar N, and preplant N plus foliar and and N-Boost. Foliar N Fertilization Study 2010 University of Nebraska South Central Ag Lab Page 4

5 Figure 3 illustrates trends in total N uptake (stover + grain N) as influenced by preplant N rate and the use of foliar N with or without N Boost. Though the only statistically significant effect on total N uptake is preplant N rate, there are trends for increased total N uptake with the application of foliar N, and additional total N uptake when N Boost is used with foliar N. 300 Total N (kg ha 1 ) Preplant & Foliar N + N Boost Preplant Fertilizer N Rate (kg ha 1 ) Figure 3. Total nitrogen uptake as influenced by preplant N rate and the application of foliar N with or without N-Boost Grain N (kg ha 1 ) Preplant & Foliar N + N Boost Preplant Fertilizer N Rate (kg ha 1 ) Figure 4. Grain nitrogen uptake as influenced by preplant N rate and the application of foliar N with or without N-Boost. Figure 4 illustrates the statistically significant effects of preplant N rate, foliar N application, and the inclusion of N Boost with foliar N on grain nitrogen uptake. Figure 5 shows fertilizer nitrogen recovery as influenced by treatment. Fertilizer N recovery fraction is calculated by subtracting mean total N uptake of the unfertilized check treatment from treatment total N uptake, and dividing by the applied N rate. Foliar N Fertilization Study 2010 University of Nebraska South Central Ag Lab Page 5

6 Fertilizer N Recovery Fraction Preplant & Foliar N + N Boost Preplant Fertilizer N Rate (kg ha 1 ) Figure 5. Fertilizer nitrogen recovery fraction as influenced by preplant N rate and the application of foliar N with or without N-Boost. There were statistically significant effects of preplant N rate on fertilizer recovery, and trends for increased fertilizer N recovery with the use of N Boost when used with foliar N application, though only at the two lower preplant N rates. There was some leaf burn following the V9 foliar application, but no evidence of any difference in leaf burn with or without the use of N Boost. There was also no negative impact on grain yield from leaf burn, as evidenced in Table 3 and Figure 2. Leaf burn gradually became less evident as the growing season progressed. Figure 6. Leaf burn at V9. Figure 7. Closeup view, leaf burn at V9. Foliar N Fertilization Study 2010 University of Nebraska South Central Ag Lab Page 6

7 Figure 8. Overview of study at V9, June 25. Figure 9. No foliar N (left) and foliar treatment (right). Summary Overall, study yields were disappointingly low. Early season compaction adversely impacted plant population and yield potential. Through approximately the V10 growth stage, plant height and color were irregular. Some leaf burn was evident following the V9 growth stage N application, but the crop soon grew out of that minor injury. Crop conditions improved as the summer progressed, and ending yields still showed benefit from foliar fertilizer treatments. Significant increases in grain yield and grain N uptake were observed with the use of N Boost, as well as trends for increased fertilizer N recovery. Foliar N Fertilization Study 2010 University of Nebraska South Central Ag Lab Page 7