Bulletin No Nitrogen Fertilization of Crested Wheatgrass in Southeastern Wyoming

Transcription

1 University of Wyoming Wyoming Scholars Repository Wyoming Agricultural Experiment Station Bulletins Agricultural Experiment Station Bulletin No Nitrogen Fertilization of Crested Wheatgrass in Southeastern Wyoming University of Wyoming Agricultural Experiment Station Follow this and additional works at: Part of the Agriculture Commons Publication nformation University of Wyoming Agricultural Experiment Station (1960). "Bulletin No Nitrogen Fertilization of Crested Wheatgrass in Southeastern Wyoming." University of Wyoming Agricultural Experiment Station Bulletin 364, This Full ssue is brought to you for free and open access by the Agricultural Experiment Station at Wyoming Scholars Repository. t has been accepted for inclusion in Wyoming Agricultural Experiment Station Bulletins by an authorized administrator of Wyoming Scholars Repository. For more information, please contact scholcom@uwyo.edu.

2 .. in Southeastern Wyoming By Wesley Seamands R. L. Lang Bulletin 364 April 1960 University of Wyoming Agricultural ~xperiment Station

3 Nitrogen Fertilization of Crested Wheatgrass in Southeastern Wyoming By Wesley J. Seamamd«and Robert Lang RES TED WHEATGRASS, a drought-resistant native of the steppes of Soviet Russia, was introduced into the United States during 1898 from an experiment station in Russian Turkestan. Since then, it has become widely accepted for reseeding dry ranges in Wyoming. t starts spring growth from two to four weeks earlier than characteristic species of shortgrass range, produces excellent hay and pasture and, in the green stages of growth, is fairly palatable to livestock. Several characteristics limit its productiveness and use. t is relatively unpalatable after maturity, is summer dormant, and tends to become low in productivity as the stand ages. The study reported in this bulletin considers the application of nitrogen fertilizer and its effects on stand and hay yield of crested wheatgrass fields in southeastern Wyoming. Limited research has been conducted on the value of nitrogen fertilizers to old established stands. From the literature dealing with nitrogen fertilization of dryland crested wheatgrass, one can generally expect increased yields from fertilization, particularly in years of high rainfall. Review of Literature n some cases tillage alone, or tillage and fertilization, or a combination of tillage, reseeding, and fertilization increased the productivity of established stands of dryland crested wheatgrass. These practices also were effective for native grasses in areas similar to eastern Wyoming. Description of the Area The soils of the Archer Substation in Laramie County, where this study was conducted, are described as Altvan loam, an extensive soil type in eastern Wyoming and in parts of Colorado. The native vegetation of the area is of typical shortgrass-plains association. The major species are blue gramagrass and buffalograss. Minor species include Western wheatgrass, needleandthreadgrass, Junegrass, Sandberg bluegrass, threadleaf sedge, and both annual and perennial forbs. The annual precipitation at the Archer Substation from 1913 to 1957 averaged in. During the 6-year period of study the mean annual and seasonal precipi- 2

4 tation was Precipitation data are shown in Table 1. During four of the six years, precipitation in the growing season exceeded the longtime average. n the remaining two years less precipitation occurred than during the 45-year average. The 6-year mean annual precipitation was about 4 percent greater during the period of study than the 45-year average. TABLE 1 - Precipitation Recorded* at the Archer Substation in Tnches of Moisture by Months, with the 6-Year and 45-Year Averages for Comparison, Year Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec. Seasonal Total precip. annual April 1 precip. to May O.H yr. avo 1952_ yr. avo * Data compiled from U.S. Deparment of Commerce, Climatological nata for Wyoming. Yearly summary. Methods of Study n 1950 and 1951, a preliminary test of the effects of nitrogenous fertilizers on the production of crested wheatgrass hay was conducted at the Archer Substation. These data were inconclusive. Between 1952 and 1957 a more comprehensive study was developed on a crested-wheatgrass field seeded in This study was designed to determine the effect of various rates of nitrogen fertilization on production and stand. The study began in April 1952 On an area of relatively uniform slope, soil, and stand density. Seven treatments using commercial ammonium nitrate (33 percent nitrogen) were: (1) 0 pound of N per acre, (2) 33 lbs., (3) 66 lbs., (4) 99 bs., (5) 132 lbs., (6) 165 lbs., and (7) 198 bs. All treatments were applied in April of each year on plots 7 x 60 ft. in size. The fertilizer was applied under the soil surface with a regular 7 ft. grain drill with fertilizer attachment. Each treatment was replicated four times on a randomized basis. A new series of plots was established each of the six years. Hay yield from the current year's fertilized plots was measured to determine the immediate effects of the treatments. Plots treated in previous years were harvested to determine residual effects. The plots were cut when the crested wheatgrass was in bloom. A 38 in. by 30 ft. strip was cut 3

5 from each treatment and the total forage weighed on a green basis. Samples of the green hay were weighed and, after oven drying, weighed again to determine percentage of dry matter. From the information obtained from the sample, the plot yield was calculated in pounds of hay per acre at 12 percent moisture. Data on stand density were obtained in late September of 1957 by a modification of the pointquadrat method. This involved counts at each foot interval of two 25 ft. tapes laid diagonally lengthwise of the plot. The 50 sample points were recorded from each plot of each series of treatments from 1952 through Stand data were analyzed on the basis of percentage stand and percentage composition with the analysis-ofvariance method. RESULTS Study of the relationship between seasonal climatological factors and hay yield disclosed that Part --Hay Yields gentle rains (those of 1 inch or less per day), had the greatest effect upon production of crested- 6.0 r-----r-----r-----,~---""'t----.., Precipitation 0# of N 33# of N 66# of N / t-----t----_1-----f-----H t f t _1-----f '--4 ~~.: ,... \ 2.0 t rlf _1-----i-----fi'-i----_ /",,' /,',,, ~... -~\ ~.~'.-;.-;~.-;... L ~ /.,;.>.> 1.0 t-----p'----'~...,.._1--_:::::; \-. \,,-V-. \...,/ " ',\,.<-",,",.~.i~..:::- "'9-...,...~'--_f_----_500,,.:.-'.> o." 2000 ~0 e E ~ 1500 ".0. ~ 1000 ~ '".;; FG. 1. Relationship between crested-wheatgrass hay yields from various nitrogen treatments and precipitation. Amounts of the precipitation graphed are those occurring in storms of 1 in. or less in the period April 1 to May 15 each year. Po "0 4

6 u ~ u~ / ~ Evaporation _ 0# of N _... _.. _ 33# of N 661 of N / -.,, z u 0 '"] 7.0 'C V '...,..,.. (/ '\ ~ <, ':. "..,",,- " ". K,,,...".., "... ','. "..",,-,»:',-.,,,- ~;...- ~...,.,: --- v" ~ ~ u u 1000 '" u 0. '"~ e g e FG. 2. Relationship between crested-wheat grass hay yields from various nitrogen treatments and evaporation from a free water surface. Evaporation is in terms of inches of water lost during the period of April 1 to May 30. wheatgrass hay. Rains of this intensity were more effective during the month of April and the first 15 days of May than earlier or later occurring moisture. (See Fig. 1.) Crested wheatgrass, in the study area, usually bloomed and was cut for hay about June 15. However, the amount of precipitation occurring between April 1 and May 15 was found to be more closely related to hay production than were total precipitation or other seasonal periods. Rain falling after May 15 did not seem to help increase hay yield, probably because the crested wheatgrass had nearly reached its maximum growth by then. Winter precipitation appeared to have little effect upon the yield of crested-wheatgrass hay. This, the authors believe, is due to snow being blown or evaporated from the fields before much moisture reached the root zone. Evaporation, as measured in inches from a free water surface during the period April 1 to June 1, was inversely related to crestedwheatgrass hay yield. (See Fig. 2.) n 1954, the year of the smallest yield, evaporation was in. Hay yield decreased from 1952 through 1954 while evaporation increased each year. The reverse was true for the years 1955 through n order to further substantiate the information presented in Figure 2, a correlation coefficient was computed for the factors involved. Average yields of all treatments for the 6-year period and for April 1 to May 15 rainfall, in storm intensities of 1 inch or less, had a correlation coefficient of The same rainfall data were tested against the various rates of nitrogen treatment and were found to have the following correlation coefficient: (1) 0 pound of N equals +,74; (2) 33 lbs. of N equal +.48; 5

7 (3) 66 lbs. of N through the 198 grass could be expected. lbs. of N treatments, averaged to- Evaporation from a free water gether because of their similarity. surface, for the period April 1 to of yield, were found to have a cor- May 30, when compared with the relation coefficient of average yield data of the five Study was made of the weather treatments of 66 pounds of data for the period 1915 through through 198 pounds of N, had a 1948 from the Cheyenne station negative correlation: and 1949 through 1955 from the Table 2 shows average yields for Archer station to determine the the seven fertilizer treatments chances of receiving this amount during the year of application. and type of precipitation. Results: Yields from fertilized plots were There is a probability of.81 of receiving 1.5 inches or more of rain- significantly greater than the nonfall in the April 1 to May 15 period. treated check except in 1954, when n other words, in four out of five no yield was recorded. Differences years, moisture favorable to nitro- between years were also highly gen response from crested wheat- significant. TABLE 2 - Yields* of Crested-wheatgrass Hay from Seven Nitrogen Treatments for Six Years. Year of Treatment Pounds of N per Acre ** Average LSD LSD N.S year Average * Yields are in pounds of hay per acre at 12 percent moisture. ** The 1954 plots were harvested, but yields were so low they were uniformly figured as zero. Table 3 shows that the average yields of crested-wheatgrass hay were increased with additional in-. crements of nitrogen, although the average increase from increments added to the 66 lb. rate was small. n this trial the most efficient use of nitrogen for the 6-year period, as a whole, was the 66 lb. rate, which gave an average gain of 6.7 lbs. per acre increase in hay production for every pound of nitrogen applied. Added increments of nitrogen, while increasing total tonnage, on the average produced progressively less hay per pound of nitrogen applied. Yield differences between years (see Table 2) were statistically significant at the 0.05 level. The 6.

8 greatest differences between yields May 15 was over 1.5 in. (1952, from the various treatments were 1956, and 1957). n 1952 all treatrecorded in the years when rain- ments produced yields which were fall during the period April 1 to significantly higher than the check TABLE 3 - Yield Response of Dryland Crested Wheatgrass As Hay to Nitrogen Fertilization Expressed in Pounds of Hay Per Acre, Percentage of Unfertilized Yields, and Nitrogen Efficiency. N Applied - lbs./acre Year and Hay Yield Average L.S.D Hay Yield (# per acre) Percent of unfertilized Lbs, gain per pound of N Hay Yield (# per acre) Percent of unfertilized Lbs, gain per pound of N Hay Yield (# per acre) Percent of unfertilized Lbs, gain per pound of N Hay Yield (# per acre) Percent of unfertilized Lbs. gain per pound of N Hay Yield (# per acre) Percent of unfertilized Lbs. gain per pound of N Average Hay Yield (# per acre) Percent of unfertilized Lbs. gain per pound of N plots. The 1956 and 1957 nitrogen treatments produced hay yields which were all significantly higher than the check plot except the 33 lbs. of N per acre treatment, which in both years was under the yield level required for significance. The most efficient use of nitrogen during 1956 was the 66 lbs. of N per acre treatment, which yielded 5.1 pounds additional hay for each pound of nitrogen applied. n 1957, a year of high precipitation (5.6 inches from April 1 to May 15), the 66 lbs. and the 99 lbs. of N per acre treatments each had a ratio of over 15 pounds of additional hay for each pound of nitrogen applied. n two years (1954 and 1955), when the rainfall was under 1.5 inches during the same period, very little hay was produced from any treatment. The 1954 yields were so low that they were figured as zero. Only the 66, 165, and 198 lbs. of N per acre treatments had yields which were significantly higher than the check plots at the 0.05 level in n 1953, rainfall of 1.42 in. received during the period April 1 to May 15 was sufficient to produce sig- 7

9 nificantly greater yields from all Complete data on residual effect treatments than were produced by of nitrogen fertilizer on crested the check plots. wheatgrass were not collected. No tests pertained to the after- However, yield responses in the math production, but visual ob- year following were tabulated servations would indicate higher three times-for 1953, 1956, and production from nitrogen-fertilized 1957-and are presented in Table 4. plots than from unfertilized. (See Only once, in 1953, was the yield Figs. 3, 4, 5, and 6). the second year after fertilization TABLE 4 - Residual Effect of Nitrogen Fertilizer on Dryland Crestedwheatgrass Hay. Yield* of Hay in Pounds per Acre at 12% Moisture Nitrogen Applied Applied Applied applied (lbs. per Harvested Harvested Harvested acre) Check Plot Average yield L.S.D. at 5% 240 N.S. N.S. 3-Year average yield * Yields reported are the mean of four replications and in each case were harvested the year after application of nitrogen. " ~,.;:;::s::.r"""hio. C't"' FG. 3. The aftermath of dryland crested wheatgrass on the check plot of the 1957 fertilizer trials. Photographed in the fall of the year of treatment. 8

10 FG. 4. The aftermath of dryland crested wheatgrass on the 198 lb. per acre 1957 application of nitrogen fertilizer. Annual forbs have been removed in the vicinity of the pencil. Compare with Figure 3. Photographed in the fall of the year of treatment. FG. 5. The check plot from the 1956 nitrogen trials. This picture shows the regrowth in the fall of

11 FG. 6. The aftermath of the 1956, 198 lb. per acre, application of nitrogen fertilizer on dryland crested wheatgrass. The picture was made in the fall of 1957, the second year after application, and shows the residual effect as compared with Figures 3, 4, and 5. significantly greater from fertil- grass will accrue mainly during the ized plots than from the non- year of application. treated check. On the basis of the A further study of residual ef- 3-year mean production figures, it fects was conducted during 1957 would appear that the benefits to from the two previous years' ferbe gained from the use of nitrogen tilization trials (Table 5). This fertilizer on dry land crested wheat- table compares yields from the TABLE Yields from 1957, 1956, and 1955 Application of Nitrogen Fertilizer on Uniform Stands of Crested Wheatgrass. Yields Are in Terms of Pounds of Hay per Acre at 12 Percent Moisture. Nitrogen Applied Applied Applied 3-Year applied average (lbs. per Harvested Harvested Harvested yield acre) Check Plot Average yield level level

12 1957 fertilizer application with those from the 1956 and 1955 application-all harvested in June of The average yields of the residual plots were equal to or slightly less than the check plots. This indicated no carry-over yield response from the fertilizer application in 1955 or Although carry-over effects of nitrogen could not be measured in significant increases in hay production, it was noted that in the fall of 1957 the aftermath growth on plots receiving 198 lbs. of N in 1952 were still easily discernible because of their dark-green color. Non-treated plots and those which had received lesser amounts of nitrogen in 1952 were yellowish green by comparison. Crude-protein content of crested wheatgrass hay was determined in 1952 and 1953 with very erratic results. Forage from the 1952 check plot contained 15 percent crude protein, while that from the 1953 check plot had 7 percent. The various treatments were not consistent, and it was impossible to draw definite conclusions about the effect of nitrogen treatments on protein content. Part Vegetative Cover and Stand A study of the ground cover Total ground cover, however, present on the various fertilized was greatest on the plots treated crested-wheatgrass plots was made with high rates of nitrogen. Anat the conclusion of the 6-year nual forbs, mainly Kochio. ecooaria, period. This study revealed that had invaded the test areas where on the average the percentage of the stand of crested wheatgrass total ground cover in crested had decreased. wheatgrass was least on those The 6-year average percentage plots which had received the heavi- of ground cover contributed by est nitrogen treatment. crested wheatgrass (Table 6) shows an inverse relationship to TABLE 6 - Percentage of Ground Cover of Crested Wheatgrass as Affected by Treatment with Various Rates of Nitrogen Fertilizer. Averages Are by Treatment and by Year. Pounds of Percentage Crested Wheatgrass Cover N Year of Treatment per acre o Average level N.S. 8 9 N.S. 9 N.S. 6-year Average

13 TABLE 7 - Percentage of Ground Cover Composed of Forbs and Species Other Than Crested Wheatgrass as Affected by Treatment with Various Rates of Nitrogen Fertilizer. Averages Are by Treatment and by Year. Pounds of Percentage Cover of Forbs and Other Plants N Year of Treatment 6-year per acre Average Average level N.S Total groun cover Forbs -"'-'" Crested Whe tgrass "OJ ;> 0 <J -0 c 60 0 " "OD... 0 OJ OD <S... "OJ <J "OJ Po< V' L L.---- / - ~...- /'...-.'....- ~--- 1-_--- _» >: L- -.>:..., ' o Pounds of nitrogen per acre FG. 7. The effect of nitrogen fertilizer on ground cover. The 6-year average for each treatment is shown in percentage of ground cover in cre ted wheatgrass and in forbs. 12

14 the amount of nitrogen fertilizer applied per acre. The check plot averaged 29 percent compared with 19 percent ground cover in crested wheatgrass on the plots treated with 198 lbs. of N per acre. The reverse was true of the percentage of cover made up by forbs and species other than crested wheatgrass (see Table 7). The relationship between nitrogen fertilization and vegetational composition is shown in Figure 7. The percentage remaining unaccounted for in crested wheatgrass and forbs was bare ground. Crested-wheatgrass stands were not significantly affected by the fertilizer treatments applied in 1952, 1955, or t may be noted from Table 6 that in 1953 only the 132, 165, and 198 lb. rates caused a significant decrease in crested-wheatgrass stand. n 1954, all nitrogen treatments caused a significant decrease in the stand of crested wheatgrass except the 132 lbs. of N treatment, and this approached significance. n the 1956 tests only those plots treated with 165 or 198 lbs, of N per acre showed a decrease in crested-wheatgrass stand. The results of this study show that in all years except 1954 (an extremely dry year), nitrogen fertilizer rates up to 99 lbs, of per acre could be applied without significant loss in the stand of crested wheatgrass. The percentage of ground cover contributed by annual forbs was significantly greater on some fertilized plots than on the check plots in all years except 1957, a year of unusually high precipitation during the growing season. This may be noted in Table 7. n the plots fertilized in 1953, 1954, and 1956, nearly all nitrogen treatments greater than 33 lbs. of N per acre caused a significant increase in the forb population. The one exception was the 99 lbs, of N treatment in 1954, which showed little forb increase when compared with the check plot. Of the plots fertilized in 1952, only those treated with 198 pounds of N per acre had significantly more forbs present in 1957 than on the check plot. n the plots treated in 1955, the 99 lbs. of N and all heavier applications showed significant forb increases. Plots treated in 1957, the year the measurements of ground cover were made, showed no significant increases in forb population due to the fertilizer treatment, although there was much taller and more vigorous growth on fertilized plots than on the checks. The forbs did not become conspicuous on the plots until after hay harvest. Crested wheatgrass, a cool-season crop, was nearly ready for harvest before the forbs had attained much growth. The protection offered by the crestedwheatgrass stubble, as well as reduced competition after harvest, afforded excellent growing conditions for the Kochia scoparia, which was the principal species present. (see Figs. 8 and 9.) n an effort to correlate weather data with both the reduced stand of crested wheatgrass and increased density of forbs, no relationship was found. t was thought that the precipitation during the growing season of the year of application would be related to the percentage of kill on fertilized. plots. However, the available weather data failed to show such relationship. 13

15 FG. 8. A portion of the crested-wheatgrass plots treated with nitrogen fertilizer in Note the forb growth, which was mostly KOCHA SCOPARA. Plot at the left received 132 lbs. of the N, at the center 33 lbs., and at the right 198 lbs. of N per acre. FG. 9. A portion of the 1956 nitrogen-fertilizer trial on crested wheatgra s, Plot at the left received 198 lbs. of N per acre. Plot at the right is the check plot, photographed in the fall of ote the annual forbs in the 19 lbs. of N plot. 14

16 Discussion Moisture, evaporation rate, and oil-nitrogen supply are limiting factors in the production of dry- nd crested-wheatgrass hay. A 6-year study at the Archer Subtation shows that of the rates tested (0, 33, 66, 99, 132, 165, and 198 lbs. of N per acre), the 66 lb. rate was the most efficient, proucing on the average 6.7 lbs. of ay for each pound of nitrogen applied. This was 88 percent more production than the average of the unfertilized plots. n 1957, a year with high spring moisture, the highest efficiency was from the 66 and 99 lb. treatments, each of which produced over 15 lbs. of additional hay for each pound of nitrogen applied. The economics of dry 1and crested-wheatgrass fer til i z a - t ion with nitrogen was not a part of this study, but nitrogen application would probably be unprofitable except (1) during years of above-average precipitation, or (2) when hay and other livestock feeds were priced extremely high. n calculating the basis of the 6-year average yields, hay at $20 per ton, and nitrogen at 15 cents a pound, the check plot produced an average of $5.00 worth of hay per acre each year. The 66 lbs. of N treatment had a 6-year average production value of $9.40 per acre but at an additional cost of $11.90, or a loss of $7.50 per acre, compared with check-plot production. With the above figures, nitrogen application would have to produce 15 an additional 15 lbs. of hay for each pound of nitrogen applied, to be economically feasible if production alone is considered. Only during the year of high precipitation, 1957, was this yield response obtained when both the 66 and the 99 lbs. of N per acre treatments produced over 15 lbs, of hay above the check yield for each pound of nitrogen applied. Other factors should be studied, including protein content of the hay and aftermath production, w hie h could show nitrogen fertilization to be more economically feasible. Other factors should be considered and given further study before definite recommendations regarding fertilization of dryland crested wheatgrass are formulated. For example, favorable response to nitrogen fertilization appeared to be closely related to a total precipitation of over 1.5 in. received in showers of under 1 inch in any 24 hours during the period from April 1 to May 15. During the six years covered by this study, only three years met this precipitation requirement, whereas the statistical probability based on the past 40 years of weather records is 4 out of 5 years. Further study is needed to determine why severe reductions in creasted-wheatgrass stands occurred with high rates of nitrogen fertilization in some years when no significant reduction occurred with the same treatment in other years.

17 Summary The influence of various rates of nitrogen fertilizer upon the hay yield and stand of dryland crested wheatgrass was studied over a period of six years at the Archer Substation in southeastern Wyoming. Nitrogen fertilization increased hay yields in all years with the exception of 1954, an extreme drought year, when there was not enough growth to warrant harvest. Based on the 6-year average, the most efficient rate of fertilization of those tested was the 66 lbs. of nitrogen per acre treatment, which gave an average yield of 6.7 pounds additional hay per pound of nitrogen applied. Higher nitrogen rates produced more total tonnage but at considerably less efficiency. Based only on 1957 yield results, the 66 and the 99 lbs. of N per acre were the most efficient in that they each yielded an additional 15 pounds of hay for each pound of N applied. Residual effect upon hay yield was not significant except in 1953, when all tests with treatment rates above the 33 lb. of N applied in 1952 resulted in significantly higher yields than the check plot. The amount of precipitation in storms of 1 inch or under during the period of from April 1 to May 15 each year was found to be closely correlated to the yield of hay. Water evaporation from a free surface during the same period showed an inverse relationship to yield. The 6-year M-ll and Conclusions ground cover of crested wheatgrass was inversely related to the amount of nitrogen applied per acre. Of the treatments tested, the loss in crested wheatgrass stand varied from 0 to 2 percent for the 33 and the 66 lbs. of nitrogen treatment, to 10 percent from plots treated with 198 lbs. of nitrogen per acre. The 6-year average percentage ground cover of forbs was directly related to increased applications of nitrogen applied per acre. Rates of 66 lbs. or more caused some increase in forb stand with an average of 10 percent from the 66 lb. rate of 38 percent stand increase from treatments of 198 lbs. of nitrogen per acre. Based on this study, one may conclude that old stands of dryland crested wheatgrass may be made more productive by adding nitrogen fertilizer. However, economic increase in yield may be expected only in years having favorable climatic conditions. t appears from this study that more than 1.5 in. of precipitation occurring in showers of 1 inch or le s during April and the first 15 days of May is necessary to obtain a high yield response from nitrogen fertilizer. No definite conclusions could be drawn from this study as to why severe reductions in crested-wheatgrass stands occur with high rates of nitrogen fertilization in some years when no significant reduction occurs with the same treataverage percentage ment in other year University of Wyoming Agricultuml Esrperiment: Station N. W. Hilston, Director Laramie