Fertilizing Malt Barley for Yield and Quality Grant D. Jackson, Ross H. McKenzie, and Allan B. Middleton Western Triangle Agric. Research Center, P.O. Box 974, Conrad, MT 59425 Email:[email protected]
Alberta Agric. Food and Rural Development, Agric. Center, 5401-1 Ave South Lethbridge, AB T1J4V6 Email:[email protected]
Email: [email protected]
Problem and Literature Review With the recent malting barley disease problems in the upper Midwest, 2-row barley is being purchased by the malt industry in the western region of the Great Plains. In Montana, only irrigated barley has been contracted for malting purposes; however, the increased demand for 2-row barley has prompted dryland barley contracts by major malting barley buyers. Nitrogen (N) is the main component of fertilizer programs for producing high quality malting barley. Quality, or the ability of the commodity to meet the needs of the grain processor, has long been a component of N fertilizer management schemes for malting barley. Kernel plumpness (plump) and protein content are the dominant quality factors associated with malt barley production, and both characteristics are directly related to N fertilization and available water. Barley that qualifies for malting must contain less than 13.5 % protein and more than 75 % plump kernels (these are current standards and may vary year to year and buyer to buyer) and is usually worth twice as much as feed barley. Nitrogen increases grain yield and protein content and depresses plump (Jackson and Dubbs, 1987; Tindall et al., 1993) while water increases yield (Hartman and Nyborg, 1989) and plump and depresses protein (Bole and Pittman, 1980). Therefore, the key to producing malt barley is judicious management of N and water, and to accomplish this goal, growers need information that considers grain quality factors as well as yield. Methods Fourteen experiments from Central, Northcentral, and the Western Triangle areas of Montana were selected for regression analysis. Selection criteria were a variation in N fertilizer rates (usually 0-120 lb. N/ac.), adequate P (usually 30 lb. P2O5/ac.) and K (usually 30 lb. K/ac.) fertility, and 2-row, malting barley cultivars with similar yield potential (Harrington and Clark). Nitrogen and K fertilizers were broadcast while planting, and P fertilizer was applied with the seed. Fertilizer materials were urea, monoammonium phosphate, and KCl. Soils were sampled just prior to planting. Regression equations were developed using initial nitrate-N in three feet of soil plus fertilizer N as the independent variable versus the following dependent variables: grain yield, grain protein content, and plump. The data were organized into two databases utilizing the maximum location yield of 70 bu./ac. as the criterion. Each database consists of seven locations. The < 70 bu./ac. database included two fallow, three no-till recrop, and two conventionally tilled recrop locations. This database had initial soil nitrate-N levels from 16 to 123 lb. N/ac. with an average of 44 lb. N/ac. The > 70 bu./ac. database contained four fallow and three no-till recrop locations and had initial soil nitrate-N levels ranging from 18 to 55 lb. N/ac. with an average of 36 lb. N/ac. The previous crop of all the recrop locations was small grains, usually barley. A second database set consisting of 15 experiments from Alberta’s Brown, Dark Brown, Thin
Black, Black, and Gray Wooded soil zones was constructed for regression analysis. All plot areas received an application of 27 lb. P2O5/ac. as 0-45-0 placed with the seed. Nitrogen treatments (urea band placed) varied between 0 and 140 lb. N/ac. Previous crops were all small grains, conventionally tilled, and the barley cultivar was Harrington. Regression equations were developed using initial nitrate-N in two feet of soil plus fertilizer N as the independent variable versus dependent variables of grain yield, grain protein content, and plump. The data were organized into two databases utilizing the maximum location yield of 100 bu./ac. as the criterion. The < 100 bu./ac. database consists of seven locations (six locations for plump), and the > 100 bu./ac. database was developed from eight locations (two were irrigated, six locations for plump). Soil nitrate N levels for the < 100 bu./ac. database ranged from 12 to 186 lb. N/ac. and averaged 62, while the > 100 bu./ac. database averaged 48 lb. N/ac. with a range from 2 to 96. Major Findings The regression equations, with selected 95 % confidence intervals (CI), showing the relationship of N on grain yield, grain protein content, and kernel plumpness are plotted in Figs. 1, 2, and 3, respectively. All equations are significant at the 95 % level or higher. Equations 1, 5, and 9 were generated from the < 70 bu./ac. Montana database or plot areas with the least amount of available water. Equations 2, 6, and 10 were derived from the > 70 bu./ac. Montana database which contained plot areas with moderate water deficits. Equations 3, 7, and 11 were calculated from the < 100 bu./ac. Alberta database that consisted of plot areas with moderate water deficits. Equations 4, 8, and 12 were constructed from the > 100 bu./ac. Alberta database that had plot areas with minimal water stress. As shown in Figure 1, equation 1 predicts the lowest yield response to N. Equations 2 and 3 are very similar in slope and predicted malt barley yield, and equation 4 predicts the highest malt barley yields. However, optimal yields occur about the same N level, 130 to 150 lb. N/ac. for all equations. Equations 1, 2, 3 and 4 had r2 values of 0.69, 0.61, 0.50 and 0.51, respectively. With malt barley, yield versus N response curves mean very little until the effects of N on protein and kernel plumpness are considered. Four distinctly different grain protein versus N response curves are shown in Figure 2. Equations 5 and 6 from the Montana data indicate positive linear responses to N with similar slopes but different positions, while the Alberta equations 7 and 8 indicate positive curvilinear and quadratic responses, respectively. With N levels that produce optimal yields or less, predicted grain protein contents of all equations are below the standard malt barley protein specification of 13.5 %. Equation 5, derived from the most water stressed areas of Montana, had the highest predicted protein levels. Equation 6, derived from moderate water deficit areas in Montana, was also linear but protein levels did not exceed 12% at the highest N levels. Equation 6 tended to predict protein levels that were 1% lower than Equ 5 at the same N levels. Equation 7 was curvilinear and protein levels approached 13% at the highest N levels of 240 lb/ac. Equation 8 was quadratic and predicted peak protein levels at 11%. Figure 3 shows the relationship of plump and N. As expected, all four locations have a negative relationship between plump and N. The Alberta equations have negative linear relationships while the Montana equations have negative curvilinear relationships. Clearly, the plump versus N relationships will dictate N fertilizer recommendations for the Montana. Equation 9 showed that as N level increases, the amount of plump kernels declined from 80 to 20%, because of limited water. Equation 10, under moderate water stress conditions, predicts that plump will decline from 90 to 60% with increasing N. In Alberta, plump is less affected by N levels, equation 11 predicts, as N levels are
increased, that plump declines from about 90 % to about 70 %. Under minimal water stress, equation 12 indicates that increasing N level had only a small effect on kernel plumpness, declining from 90 to 80 %. Applied Questions 1. How much nitrogen fertilizer is required to achieve optimum malt barley yield? Producers must consider malting barley yield potential as a starting point. This should be based on soil water level at the time of seeding in combination with average growing season precipitation or irrigation level. Then, using the appropriate equation (1 to 4) of barley yield response to total N (soil N + fertilizer N) can be used to estimate the amount of nitrogen required to achieve the estimated yield potential. The amount of N fertilizer required should be modified based on the cost of N fertilizer and the value of the type of malting barley, to ensure the rate selected is economical. Then, the amount of N must be modified to ensure that protein levels can be kept under 13.5% (equations 5 to 8) and kernel plumpness will not decline below 75 to 80 % (equations 9 to 12). 2. What effect does nitrogen have on malt barley protein levels? The results from the research trials in Alberta and Montana suggest that under very good to optimum water, fertilizing with N for optimum yield generally will not result in protein levels over 13.5%. However, as water stress level and N level increase, the probability of protein levels over 13.5% also increase. Therefore, the amount of N application must consider not only the effect on yield but on protein as well. 3. What effect does increasing nitrogen rate have on plumpness of malting barley? Results in Figure 3 clearly show that as N level increases, the level of plumpness decreases. The negative effect of N on plumpness is greatest when water is most limiting (equation 9) and is the least when water is very good to optimum (equation 12). 4. What role does water play in yield potential, protein level and kernel plumpness? From Figures 1, 2 and 3 the effect of N and water are clear. Under greatest water deficit, malting barley yields are the lowest (equation 1), protein levels are the highest (equation 5) and percentage of plump kernels is lowest (equation 9). Conversely, when water is very good to optimum, yields are the highest (equation 4), protein levels are moderate (equation 8) and percentage of plump kernels will be higher than the minimum malt barley standard (equation 12). Acknowledgements The authors gratefully acknowledge funding support from the Montana Agricultural Experiment Station and from Canadian agencies including the Alberta Agricultural Research Institute, FFF OnFarm Demonstration, Alberta Barley Commission, Westco, and Agrium. We gratefully acknowledge the field staff at Montana State University, Western Triangle Agricultural Research Center and Alberta Agriculture, Food and Rural Development for assistance in conducting the field trials, as well as the Montana State University Soil Testing Laboratory and Agri-Food Laboratory Branch, Alberta Agriculture, Food and Rural Development for soil and seed analysis.
References Bole, J.B., and U.J. Pittman. 1980. Spring soil water, precipitation, and nitrogen fertilizer: Effect on barley grain protein content and nitrogen yield. Can. J. Soil Sci. 60:471-477. Hartman, M.D., and M Nyborg. 1989. Effect of early growing season water stress on barley utilization of broadcast-incorporated and deep-banded urea. Can. J. Soil Sci. 69:381-389. Jackson, G.D., and A.L. Dubbs. 1987. Spring wheat and barley response to urea fertilizer placement and nitrogen rate. Montana AgResearch 4(1):10-13. Tindall, T.A., J.C. Stark, and B.D. Brown. 1993. Nutrient Management. p. 21-23. In L.D. Robertson and J.C. Stark (ed.) Idaho Spring Barley Production Guide. Bull. No. 742. Idaho Coop. Ext. Ser., Moscow.