Wheat Responses to Copper and Other Micronutrients
Dr. Dave Franzen
NDSU Extension Soil Specialist
Fargo, ND
INTRODUCTION
Wheat has a special need for copper and is classified as a relatively sensitive crop to copper deficiency (Brown, 1977). Copper deficiency is most commonly found in organic soils (soils with organic matter levels greater than 10%) and is common in many crops under organic soil conditions. However, deficiency in mineral soils is also possible. Australian research has documented small grain copper deficiency on mineral during the last thirty years (Graham and Nambiar, 1981). Canadian research within the last ten years has shown that copper deficiency is possible in mineral soils, especially low organic matter, coarse textured soils (Karamanos et al., 1986). Their research found that the DTPA soil test was a good indicator of copper deficiency, with a critical level of 0.4 ppm for wheat and 0.3 for flax. NDSU recommendations previous to this study was 0.2 ppm. Soil treatments with copper sulfate and chelates were found effective in Canadian work, while foliar treatments were not.
Copper deficiency symptoms were described by Evans et al. (1994) and Solberg et al. (1995). Symptoms were seen on Black, Gray-Black and Dark Brown soils of Alberta. They occur in irregular patches, sometimes with a browning discoloration called "stem melanosis" (Piening et al., 1987) or ergot infection. There is also an increase in take-all and take-all symptoms. Deficiencies also result in yield reductions, with a slight deficiency, 10-20% yield reduction, moderate, 20-50%, 50-100% at severe deficiencies. Other symptoms may include limpness at mid-tillering or stem elongation, pale yellow, curled young leaves at tillering, leaf-tip death (pigtailing), increased susceptibility to disease, retarded stem elongation, excessive late tillering, delay in heading, aborted heads and spikelets, and delay in maturity. Graham (1975) found that copper deficiency leads to pollen sterility. Evans (1990) postulated that pollen sterility may lead to extended flower opening, resulting in increased ergot infection.
Plant or leaf analysis has not been found to be helpful in diagnosis of copper deficiency (Hill, 1979; Longeragan et al. 1980). Soil testing using the DTPA extraction method has been found to be a good indicator in the right soils (Liang et al., 1991).
Australians have found that copper application may be helpful for many years, so the initial cost of application can be spread out over several crops (Gartrell, 1980).
An initial investigation on oats in North Dakota revealed no yield increases from copper. (Dahnke et al., 1984). Recent preliminary Montana studies on silt loam and heavier soils did not show yield increases (Jacobsen, personal communication, 1998). However, a 1996 study (Franzen and McMullen, 1997), found a decrease in head discoloration with copper application near Mapleton, ND. The success of that study led to investigations in 1998 in which a yield increase was recorded with copper application.
Studies leading to this research
1998 copper application
Methods
Copper trials were established at six locations (Table 1). Two locations were in a forty-acre field where site-specific research has been conducted for four years southeast of Valley City, ND about 3 miles. Two locations were in Wells county, southwest of Devils Lake, and two were in Benson county, west of Devils Lake. Treatments consisted of a 5 lb/acre Cu application as copper sulfate (25%) and an untreated control, as a randomized complete block design with 8 reps. Plot size was 20 feet by 10 feet. Harvest was made of two rows, 20 feet long. Disease readings were made during the growing season at four locations. Grain will be rated for disease at a later date for all six locations.
Table 1. Soil test data for the six experiments in 1998.
OM, % Texture Cu, ppm pH
Valley City 1 1.8 Sandy loam 0.4 6.0
Valley City 2 3.5 Loam 0.4 6.4
Wells 1 2.6 Loam 0.4 7.1
Wells 2 2.3 Loam 0.5 7.6
Benson 1 3.2 Loam 0.4 6.8
Benson 2 4.2 Loam 0.4 7.4
Results
Of the six locations, the only one with a yield increase was the Valley City 1 site, however the degree of increase, 15.6 bu/acre, was large and highly significant (Table 2.). Visual differences between treated and untreated plots were evident from the four leaf stage of growth (Feekes 4). Scab incidence, scab severity, and field scab severity ratings were all significantly lower at Valley City 1, using the 10% probability level of significance (Table 3, 4 and 5). Field scab severity ratings were also lower with copper application at the Benson 1 site. No differences at any site were observed on leaf diseases or black chaff ratings with copper application.
Table 2. Yield for the six experiments in 1998.
------------ Yield, bu/acre ----------------
Site With Copper Without Copper F Significance
Valley City 1 39.7 24.1 16.3 P< 0.01
Valley City 2 60.5 55.5 0.9 NS
Benson 1 24.7 24.2 0.19 NS
Benson 2 37.6 39.1 0.50 NS
Wells 1 36.1 36.5 0.14 NS
Wells 2 36.3 41.0 1.70 NS
1999 and 2000 Research
Methods
Eleven sites were planned for the 1999 growing season. Originally ten sites were planned, but due to fear of hail or another natural disaster, an extra site was worked into the study. Cooperators were located with the help of county extension agents and in some cases through previous contacts made by the researchers. No pre-screening of sites was conducted, except the word of the cooperator that no manure had been applied to the sites during the last ten years. Sites were located on slopes or hilltops according to the results of the 1998 survey of copper soil test levels. The sites were as follows-
Bowman, ND- spring wheat
New Leipzig, ND- spring wheat
Menoken, ND - spring wheat
Valley City, ND - spring wheat
New Rockford, ND - spring wheat
Embden, ND - spring wheat
Arthur, ND - spring wheat
Crosby, ND - spring wheat
Richardton, ND - spring wheat
Minot, ND - durum
Keene, ND - durum
The Bowman, New Leipzig and Menoken sites were treated with copper treatments in mid-March when soils were dry and thawed to at least two feet in depth. The remaining sites were wet enough that treatments were delayed until directly before seeding.
Because of continued wet weather through the spring, especially in the northwest, seeding was delayed at the Keene and Crosby until mid-June. Seeding at Richardton was delayed until mid-June, and following our 5-leaf foliar treatment (at which time the wheat looked robust and there was adequate moisture throughout the profile) the wheat mysteriously died and the field was lost to our study.
Two sites were lost because of prevented planting. The site at Bowman was not seeded, although three times the cooperator tried to seed, but buried his tractor each time. The field at Minot was covered with water for much of the seeding season and was finally abandoned to seeding. The eight sites that remained were treated, measurements taken and yields were obtained at harvest.
Copper treatments were as follows-
check (0 copper)
1.25 lb/acre as CuSO4 soil applied
2.5 lb/acre as CuSO4 soil applied
3.75 lb/acre as CuSO4 soil applied
5.0 lb/acre as CuSO4 soil applied
0.5 lb/acre as 7.5% Cu Chelate (EDTA) applied at 4-5 leaf stage.
To ensure that all treatments received the same amounts of sulfur, a uniform application of 15 lb/a of N as urea and ammonium sulfate and 7.5 lb/a of S as ammonium sulfate/copper sulfate was applied in each treatment. Rates of urea and ammonium sulfate were varied to compensate for the sulfur contributed by each copper treatment. Check plots received this amendment as well as soil and foliar treatments. Following crop emergence, about the 4-5 leaf stage, plots were revisited, the cans located with a GPS unit and a metal detector and the flags replaced for the rest of the season. The foliar treatment was usually made at this time.
At early heading, measurements were made of tiller number, plant height and relative maturity. Disease measurements were made at four locations- New Leipzig, Arthur, Embden and Valley City. Disease measurements were made using four of the eight replicates available.
2000
Methods in 2000 were similar to 2000, but with additional site screening in place. In order to increase the possibility of a yield response, cooperators were contacted in March regarding their interest in the study. Field visits were made at each of twelve locations and two fields were screened for soil copper levels by taking three separate samples from an area with lower organic matter and coarser texture within each field. Samples were analyzed and the field not only with the lowest copper level, but also with the most uniform copper levels were selected for the study.
Residual copper treatment sites were located at Bowman from the abandoned and unseeded 1999 copper trial and an additional site was evaluated from the 1998 Valley City site where a significant yield response was seen that year.
Treatments in 2000 were similar to 1999 treatments, except for the Valley City 1998 residual copper study, where the treatments were a check and a 5 lb Cu/acre treatment as copper sulfate (25%), with six replications. Also, a uniform application of 50 lb N/acre as urea was applied to all plots, since lower N rates contribute to copper translocation in plants, and would mask potential copper deficiency. Six replications were used in all 2000 studies as compared to eight in 1999. Disease measurements for scab and leaf diseases were made at all sites, however, some ratings were made past an optimum date and the data was not considered in the results. An additional site southeast of Minot was also installed, but abandoned due to persistent wet weather at harvest, resulting in sprout damage and questionable yields that might have resulted from harvest.
RESULTS
1999
Out of the eight sites, only one site, New Rockford, had a yield increase due to copper application. Data from the other seven sites are not displayed, but the New Rockford data appears in Table 3.
There was a yield increase due to a 2.5 lb/a Cu treatment against the check at New Rockford. This is a low organic matter, sandy site, similar to the area in which a yield increase was recorded in 1998. Unlike Valley City 1 in 1998, the copper treatments at New Rockford and other locations did not stand out visually from surrounding areas. Although measurable differences were sometimes seen, the affects were subtle and only revealed through careful measurement. It was also troubling that the yield increases were not consistent among copper application rates, but only appeared at the 2.5 lb copper rate.
Table 3. Copper effects at New Rockford, 1999.
Treatment Yield Test wt. Protein Tillers Growth Stage Plant height
bu/a lb/bu % inches
Check 31.6 55.8 12.7 1.1 2.4 29.5
1.25 lb/a Cu 33.3 57.1 12.3 1.7 1.9 30.4
2.5 lb/a Cu 36.1 56.9 12.6 1.4 2.4 30.4
3.75 lb/a Cu 29.1 56.3 12.0 1.1 2.6 28.6
5.0 lb/a Cu 32.0 56.5 12.4 1.7 2.3 30.6
0.5 lb/a Cu 31.3 56.1 12.0 1.0 2.6 29.4
foliar
LSD 10% 4.1 0.6 NS 0.6 NS NS
A summary of all the statistical significance of all measurements is given in Table 4. There were test weight differences measured at New Rockford and Embden. There were no differences in grain protein at any site. Growth stage at heading was advanced for copper treatments at Arthur, compared at the 10% probability level. Tillering was increased at the 10 % level at New Rockford. Plant height was greater with soil applied copper at Valley City at the 10% level. Leaf rust was decreased at Valley City (P<10%) and at Arthur (P<1%). Scab incidence was lower with copper treatment at Arthur and at Embden (P<5%).
Table 4. Summary of statistical significance of measurements, copper study, 1999.
|
Site |
Yield bu/acre |
Test Weight |
Protein % |
Tiller Number |
Growth Stage |
Plant Height |
Septoria |
Leaf Rust |
Scab Incidence |
Scab Severity |
|
New Leipzig |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
|||
|
Menoken |
NS |
NS |
NS |
NS |
NS |
NS |
||||
|
Valley C |
NS |
NS |
NS |
NS |
NS |
10% |
NS |
10% |
NS |
NS |
|
Arthur |
NS |
NS |
NS |
NS |
10% |
NS |
NS |
1% |
5% |
NS |
|
New R. |
5% |
<1% |
NS |
10% |
NS |
NS |
||||
|
Embden |
NS |
10% |
NS |
NS |
NS |
5% |
NS |
|||
|
Keene |
NS |
NS |
NS |
|||||||
|
Crosby |
NS |
NS |
NS |
Summary of 1999 work-
The site with the significant yield response was on a low organic matter, sandy soil with a zero tillage system, similar to the responsive site in 1998. Sandy, low organic matter soils appear to be more responsive than heavier textured soils higher in organic matter. Another factor not previously considered is tillage following application. Two sites that appeared to fall into the categories of the 1998 and 1999 yield responses ( Embden and Menoken) did not give yield responses to copper. It may be possible that the deep tillage diluted the application so that the full effect was not evident in this year. The results this year show that there may be a value to copper application on certain soils in North Dakota, and support the initial findings in 1998.
2000
Twelve sites were evaluated for yield, but only one recorded a significant yield increase.
A significant yield increase of 3.3 bu/acre was recorded at the Napolean site (Table 5). Significant yield increases were not seen at any other site, including the residual plots at Bowman and Valley City 1. Reductions in scab incidence and severity were observed at Arthur and the residual copper plot at Valley City 1 (Table 5). Lower scab severity was recorded at Northwood. Lower Septoria leaf disease levels were observed at Northwood.
The lack of yield response at many sites was surprising. At Taylor and at Bowman, plants near or in the experiment showed copper deficiency symptoms of pigtailing of leaves, however, copper had no effect on yield. It is possible, since much of the yield at Valley City1 in 1998 was probably due to increased tillering, and increased tillering was found at New Rockford in 1999, that the dry early season in much of North Dakota prevented either the uptake of copper early enough in the season, or prevented increased tillering that might have resulted in yield increases.
The yield increase at Napolean was not consistent throughout all copper treatments. As in New Rockford in 1999, the yield increase came from the 2.5 lb Cu/acre treatment, but not from the others (Table 6). Protein decreased from the check with the foliar treatment at the Rutland site and was lower than the check for the 2.5 and 3.75 lb Cu treatment at the 1999 Bowman site.
Table 5. Yield summary at Napolean, 2000.
Treatment Yield Test weight
lb Cu/acre bu/acre lb/bu
0 28.2b 54.6
1.25 29.6a 54.5
2.5 31.5a 54.3
3.75 26.2b 54.7
5.0 29.2a 54.4
0.5 foliar 28.5a 54.4
LSD 5% 3.2 bu/a NS
Summary-
Copper has some affect on wheat and durum yields in North Dakota. Twenty sites were investigated. Sites were selected with the most favorable characteristics for copper deficiency, such as low organic matter, landscape position (hilltop or slope) and coarse textures. Out of these twenty sites, two showed yield increases to copper application. Both were sandy soils, however the site at Napolean tested >3% organic matter, which is contrary to what was expected. However, the organic matter at this site might not be truly organic matter, but instead slightly decomposed residue, since the site had been in CRP for several years prior to 2000. Five sites showed a decrease in scab incidence and/or severity due to copper application, including a residual copper site. Two sites showed a small decrease in leaf rust in 1999, while one site showed a small decrease in leaf spotting in 2000. Inconsistent decreases in protein levels were seen at two sites in 2000.
It is evident from these studies that copper responses are possible. The frequency of responses is not high. Residual copper has value, but not necessarily in guaranteed yield increases. There is some affect on scab incidence and severity, but not entirely consistent. Copper application, if conducted, would best be made in a directed manner towards soils at risk, with the understanding that yield increases are not guaranteed due to its application. The high cost of 2.5 lb Cu/acre makes it difficult to justify a 3-4 bushel/acre response part of the time.
Table 6. Summary of the effect of copper fertilizer on yield and disease, 2000.
|
Site |
Yield bu/acre |
Test Weight |
Protein % |
Septoria |
Leaf Rust |
Scab Incidence |
Scab Severity |
|
Bowman 1999 |
NS |
NS |
10% |
x |
x |
NS |
NS |
|
Bowman 2000 |
NS |
NS |
NS |
x |
x |
NS |
NS |
|
Taylor |
NS |
NS |
NS |
x |
x |
NS |
NS |
|
Medina |
NS |
NS |
NS |
x |
x |
NS |
NS |
|
Napolean |
5% |
NS |
NS |
x |
x |
x |
x |
|
Thilmony 2000 |
NS |
NS |
NS |
x |
x |
NS |
NS |
|
Thilmony 1998 |
NS |
NS |
NS |
x |
x |
1% |
1% |
|
New Rockford |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
|
Rutland |
NS |
NS |
10% |
NS |
NS |
NS |
NS |
|
Arthur |
NS |
NS |
NS |
x |
x |
5% |
10% |
|
Northwood |
NS |
NS |
NS |
5% |
NS |
NS |
5% |
|
LaMoure |
NS |
NS |
NS |
x |
x |
x |
x |
|
Minot |
x |
x |
x |
NS = nonsignificant at 10% level or less. x = disease readings made too late to be meaningful.
Responses to copper were observed when soil DTPA copper levels were below 0.6 ppm. Therefore, NDSU recommendations will be adjusted for small grains only to 0.6 ppm or less. However, copper soil test alone did not adequately predict the frequency or magnitude of responses. Sites with very low copper levels, such as Bowman, were not responsive in yield. Also, sites with loam textures and heavier would not be expected to respond regardless of soil test Cu levels. Sandier soils with organic matter lower than 2% would be most susceptible to copper deficiency.
One aspect of copper fertilization not addressed is differences in varieties to copper deficiency. In most micronutrient situations, variety places an important role. However, 2375 spring wheat and Oxen spring wheat were the two varieties which happened to be in responsive experiments in 1999 and 2000, but other sites also were grown to these varieties and did not express deficiency.
The following are general guidelines for Cu use in North Dakota.
-Soils with organic matter higher than 2% and/or soil texture heavier than sandy loam should not be at risk of Cu deficiency.
-If soils are less than 2% organic matter, and are sandy loam textured or coarser, wheat and durum may respond if soil Cu levels are less than 0.6 ppm DTPA.
-Hilltops and slopes with low organic matter and sandy texture are most at risk.
-The probability of significant yield increases due to copper on our at-risk soils with low soil Cu levels is only about 20%.
-Foliar Cu application was not effective in disease prevention or yield enhancement at the 4-5 leaf stage.
-An application of Cu sulfate (25% Cu) at a 2.5 lb active Cu rate per acre is adequate to see a response if a response will occur.
-Cu application will remain residual for several years, however the residual may or may not increase yields in subsequent years, depending on environmental and physiological factors.
-Scab was decreased at some sites by copper application, but would not be as affective as a fungicide.
Responses of wheat to other micronutrients.
The response of wheat to other micronutrients is rare. Manganese and boron are two micronutrients which are rarely deficient in the region in even the most sensitive crops. Manganese deficiency can be induced in the greenhouse on wheat when a foliar application of iron is made, but field deficiencies have been rarely documented. Boron deficiencies of small grain have likewise not been documented.
Some rare occurrences of zinc deficiency has been noted in Canada, but not in North Dakota. These areas of deficiency are localized. Deficiency symptoms are confined to small areas within fields of poor growth, with wheat leaves appearing blotchy, with the blotchiness not associated with disease organisms. In Turkey, responses to zinc were seen on soils with a calcium carbonate equivalence of 38% and a DTPA zinc test of 0.12 ppm. The results of a North Dakota greenhouse experiment on wheat are shown in Table 7.
Table 7. Response of flax, dry bean and wheat to
zinc on a low zinc testing soil. Moraghan, 1984.
Fertilizer
Zn Dry beans Flax Wheat
ppm -------- dry matter, g ---------
0 2.8 3.1 10.0
16 6.6 4.8 10.3
significance yes yes no
Wheat was not responsive to zinc even on a soil where dry bean dry matter yield more than doubled with the application of zinc. Wheat appears to be very adapted to low zinc levels in the region.
Iron chlorosis can sometimes be seen on wheat on high carbonate, high soluble salt soils in the region. The affected plants are usually near saline areas around potholes or roadside ditches. Wheat is usually tolerant to low soil iron availability in our region, however, the presence of high salinity appears to break down the natural tolerance. Because of the yield lowering effect of salinity itself on the wheat, it would not be effective to treat the wheat with an iron supplement. The long-term solution for these small areas would be to lower the water table through increased cropping intensity or drainage, thereby lowering the salinity in the field.
References
Brown, J.C., and R.B. Clark. 1977. Copper as essential to wheat production. Plant Soil 48:509- 523.
Dahnke, 1984, 1985 Crop Production Guide p. 169. NDSU Ext. Serv. and NDAA.
Evans, I. 1990. Grainnews, Sept. 1990.
Evans, I.R., D.C. Maurice, D.C. Penney, and E.D. Solberg. 1994. Disease susceptibility and major yield depression in wheat correlated with copper deficient soil In L.S. Murphy (ed.) Proc. Intensive Wheat Management Conference, Denver, CO, 10-11 March, 1994. PPI/FAR.
Franzen, D., and Marcia McMullen. 1996. 1997 Crop Production Guide. NDSU Ext. Serv. and NDAA.
Franzen, D.W. 1999. North Dakota survey of soil copper, pH, zinc and boron levels. NDSU Extension Report 52.
Gartrell, J.W. 1980. Residual effectiveness of copper fertilization for wheat in western Australia. Aust. J. Exp. Agric. Anim. Husb. 20:370-376.
Graham, R.D. 1975. Male sterility in wheat plants deficient in copper. Nature 254:514-515.
Graham, R.D. and E.K. S. Nambiar. 1981. Advances in research on copper deficiency in cereals. Australian Journal for Agricultural Research 32:1009-1037.
Hill, J., A.D. Robson, and J.F. Loneragan. 1979. The effect of copper supply on the senescence and retranslocation of nutrients of the oldest leaf of wheat. Ann. Bot. (London) 44:279-287.
Karamanos, R.E., G.A. Kruger, and J.W.B Stewart. 1986. Copper deficiency in cereal and oilseed crops in northern Canadian prairie soils. Agron. J. 78:317-323.
Longeragan, J.F., K. Snowball, and A.D. Robson. 1980. Copper supply in relation to content and redistribution of copper among organs of the wheat plant. Ann. Bot. (London) 45:621- 623.
Moraghan, J.T. 1984. Susceptibility of different crops to zinc deficiency. 1984 Crop Production Guide. NDSU Ext. Service and the North Dakota Ag Association, Fargo, ND.
Piening, L.J., D.J. McPherson, and S.S. Mahli. 1987. The effects of copper in reducing stem melanosis of Park wheat. Can. J. Plant Sci. 67:1089-1091.
Solberg, E., I. Evans, D. Penny, and D. Martin. 1995. Copper deficiency in cereal crops. Agri-fax Agdex 532-2, Alberta Agric., Food and Rural Devel., Edmonton, AB,Canada.
Acknowledgements-
Thanks to SBARE, Cenex Land O’ Lakes and Agrium for providing funding for this work.