ProCrop

Forty Years of Nitrogen Fertilization of Bromegrass

The value of nitrogen fertilization of tamegrass has been known for more than 50 years, yet fertilization of tamegrass pastures or haylands in North Dakota is limited. A variety of reason are given including an increase in the annual variation of forage supply and low pasture rental rates. The following is a brief summary of a long-term fertilization experiment conducted at Fargo.

Bromegrass was established prior to 1929, the exact date or variety is unknown. During the 1954 fall, Dr. Jack Carter, Professor Emeritus of the Plant Sciences Department, initiated this experiment by applying ammonium nitrate (34-0-0) at six rates, 0, 33, 66, 133, 200, and 266 lb N/a. A randomized complete-block design with two replicates was used. The nitrogen treatments have been applied each year in October for a total of 40 years. Forage yields have been determined each year at anthesis growth stage (from June 15 to 28) and during September (24 of 40 years) when rainfall was adequate on the east half of each treatment. The west half of each treatment was harvested for seed for the first 25 years and subsequently for forage 3 to 4 weeks after anthesis (a second harvest has never been taken on these plots). Crude protein in the forage has been determined many years.

Carter (1961) summarized the first 6 years. He found forage yields to double with application of 66 lb N/a. Crude protein increased significantly at 200 lb N/a. Larson et al. (1971) found up to 700 lb N/a of nitrate-nitrogen in the soil in the 266 lb N/a treatment after 15 years of fertilization, but all nitrate nitrogen was within the rooting depth of the bromegrass. Meyer et al. (1977) compared long and short-term effects of fertilization and found little differences other than an increased crude protein content at 133 lb N/a. They reported recovery rates of applied nitrogen as crude protein ranging from 40% in a dry year to 120% in wet years.

Vigil (1977) found no difference in acid-detergent fiber, neutral-detergent fiber, and most other quality parameters by fertilization level at the hay stage. Nitrate-nitrogen accumulated in the forage with nitrogen fertilization rates above the 133 lb N/a. Meyer and Dahnke (1981) found the pH of the plow layer to be 5.4 at 266 lb N/a compared with 7.1 at 66 lb N/a after 25 years of fertilization. They also found the potassium and phosphorus soil test levels decreased while manganese and iron levels increased with increasing fertilization rate. Meyer (1989) found the yield response curves between wet and drought years were similar; although the magnitude was different.

Forage yields have been doubled by an application of 66 lb N/a, similar to results reported by Carter (1961) for the first 6 years (Table 1). Forage yields however have been slightly less at high fertility rates the last 20 years than the first 20 years. Part of the difference has been due to fewer years when a second harvest was obtained. Although stands have varied, they are considered adequate for forage production and not a factor in the yield differences.

The first harvest yield is about 0.2 tons/acre higher across all fertility levels when harvested about 3 weeks after anthesis then harvest at anthesis (Table 2). A second harvest occurred 60% of the years in this experiment and contributes more to the high fertility treatments than the low.

Crude protein concentration of the hay increases with fertilization level especially at 133 lb N/a and above (Table 3). Crude protein concentration has been less at the high fertilization rates in the second harvest hays in 1990-1994 than in the 1972-76. This probably indicates a loss of accumulated soil N due to the wet years in 1993 and 1994. Much of the soil N loss was probably due to denitrification (Larson et al., 1971; Meyer and Dahnke, 1981).

These data confirm our recommendation of 70 to 100 lb N/a annual fertilization on tamegrass in eastern North Dakota. Several experiments by Dodds (1975) and others indicate that 40 to 60 lb N/a is optimum for central to western North Dakota.

Nitrogen fertilization increased grass hay yields and protein content. High protein content is especially important during gestation and winter rations.

References-

Dodds, D.L. 1975. Grassland fertilizer demonstration and yield tests. ND Coop. Ext. Service Grass-n-Beef No. 9 and 11.

Carter, J.F. 1961. Nitrogen fertilizer increases yields of pure grass pastures and meadows. ND Farm Res. 21 (12):4-8

Larson, K.L., J.F. Carter and E.H. Vasey. 1971. Nitrate-nitrogen accumulation under bromegrass sod fertilized annually six levels of nitrogen for fifteen years. Agron. J. 63:527-528.

Meyer, D.W. 1989. Effects of nitrogen fertilization of bromegrass at six levels for 35 years. p. 246. In Agron Abstr. ASA, Madison, WI.

Meyer, D.W., J.F. Carter, and F.R. Vigil. 1977. Bromegrass fertilization at six nitrogen rates: Long and short-term effects. ND Farm Res. 34(6):13-17.

Meyer. D.W., and W.C. Dahnke. 1981. Selected chemical properties of Fargo clay soil after 25 years of nitrogen fertilization of bromegrass at six rates. p. 184. In Agron. Abstr. ASA, Madison, WI.

Vigil, F.R. 1977. Bromegrass (Bromus inermix Leyss.) yield and quality as affected by long-term nitrogen fertilization. Ph.D. dissertation. North Dakota State Univ. Fargo.

*Cut-1 was taken about 3 weeks after anthesis.

Back to Fertilization - Hay Menu
Back to Hay Menu
Back to Main ProCrop Index

Further contact information