Evaluating N Fertilizer Sources and Timing for Winter Wheat¹

Abstract

Ammonia volatilization can reduce the effectiveness of surface applied N fertilizers. Our objectives were to evaluate N source by timing interaction under field conditions conducive to NH3 volatilization and to compare the sensitivity of three approaches to assessing N source by timing interaction. Ammonium nitrate and urea fertilizers were topdressed at rates of 0, 34, 67, and 101 kg N/ha on 19 November or 23 March to ‘Winalta’ winter wheat (Triticum aestivum L.) grown on a nonirrigated Scobey silt loam (Aridic Argiboroll, fine, montmorillonitic). Plots receiving topdressed N contained sub‐plots fertilized at the appropriate rate and time with 15NH4 15NO3 or 15NH2CO15NH2 labeled fertilizers containing 1.31 atom percent 15N. Nitrogen fertilization increased straw yield, grain yield, grain protein, test weight, and N content of straw and grain. Uptake of soil N and fertilizer N in straw and grain were determined. Grain yield was fitted to a concurrent Mitscherlich regression model while total N uptake and fertilizer N uptake were fitted to multiple linear regression models to evaluate the relative effectiveness of each N source—timing combination. Comparison of regression coefficients for either grain yield or total N uptake revealed no significant differences between N source—timing combinations. Fertilizer N uptake regressed on rate of applied N was a better parameter for evaluating N source by timing interaction and showed that fall topdressed urea was only 69% as effective as fall topdressed ammonium nitrate. Spring topdressed urea, spring topdressed ammonium nitrate, and fall topdressed ammonium nitrate were equally effective in supplying N to wheat plants. Volatilization of NH3 from surface applied fertilizer probably accounts for the lower relative effectiveness of urea topdressed on 19 November.

Fertilizer Rate and Placement Alters Triticale Forage Yield and Quality

“…The increase in N fertilization also improved forage quality by reducing fiber concentrations and increasing crude protein content, thus producing a higher quality product. The N‐deficient soil and adequate moisture enabled significant yield increases with as much as 120 lb of N per acre, which is a positive response to N level greater than typically seen in dryland cereal grain production research in the western Great Plains (6, 21). The addition of P fertilizer up to 15 lb/acre also positively influenced forage yield more than any other trait, and small increases in P level had a greater yield response than increases in N level.…”

“…Without banded P, NDF was near 62.2%, while NDF was near 64.0% when seed banded P was added at 5 to 15 lb/acre ( Table 6). Level of P had no effect on ADF value of forage (Table 5 and 6). Forage yield and banded P fertilizer rates were inversely related with forage quality.…”

“…The level of NDF differed significantly in each of the three years, with a low of 61.6% in 1998 and a high of 64.5% in 2000. No interaction existed between broadcast N and seed banded P rate for ADF in any year ( Table 5), but increased broadcast N rate did gradually lower ADF linearly ( Table 5 and 6). When averaged across broadcast N rates, the addition of banded P increased ADF 1.4% (Table 6).…”

“…Across several sites in Kansas, Schlegel et al (21) found that dryland winter wheat grain yield increased as urea‐ammonium nitrate solution was increased up to 100 lb of N per acre. Dryland winter wheat grain yield in Montana also showed a positive response to urea and ammonium nitrate applied either in the fall or spring with 89 lb of N per acre (6). Winter wheat dry matter yield harvested at heading increased and water use efficiency plateaued when N fertilization reached 50 lb/acre in Colorado (15).…”

Makarnalık Buğdayda (Triticum durum L.) Sulama ve Azotlu Gübrelemenin Verim ve Verim Öğeleri Üzerine Etkisi

“…K ış l ı k tah ı llara yazl ı k olarak verilen azotlu gübre ikiye bölünerek verildi ğ i zaman vejetatif ve generatif geli şmeyi dengeli bir şekilde art ı rmaktad ı r. Bu nedenle hem birim alandan elde edilen biyolojik verim, hem de tane verimi artmaktad ı r. Dengeli geli şen bitkide tane verimi daha fazla art ış göstermektedir. Meints (1982), Duwayri (1984), Hagras (1985), Baran (1997), yapt ı klar ı çal ışmalarda bu ğdaya uygulanan su ve azot dozlar ı ndaki art ışı n birim alandan elde edilen biyolojik verimi ve birim alan hasat indeksini art ı rd ığı n ı belirtmi şlerdir.…”