Illinois Fertilizer
Conference Proceedings
January 23-25, 1995
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D. Bullock, G. Bollero, M. Cender, R. Farnsworth, T. Holsapple, T. Hortin1
Environmental and economic concerns have fueled interest in agriculture's economic competitiveness, soil erosion, N fertilizer efficiency, and nitrate leaching (Heichel and Barnes, 1984). We believe that these concerns will result in legislation, at both the federal and state levels, regulating N fertilizer and tillage use for summer feed grain crops in Illinois. Winter cover crops will probably be required in this legislation. The cover crop will be either a legume which produces significant amounts of organic nitrogen via nitrogen fixation or a small grain which scavenges residual soil nitrates for the production of organic nitrogen and consequently reduces the amount of nitrates available for over-winter leaching.
Many winter cover crops can be used to reduce soil erosion and provide organic N. In the lower Corn Belt hairy vetch (Vicia villosa Roth.) is the preferred legume while rye (Secale cereale) is the preferred non-legume (Ebelhar et al. 1984, Frye et al. 1988). Most research indicates that hairy vetch contributes an equivalent of 60 to 90 pounds N per acre, but resulting yields are not usually economically competitive with corn receiving the normal 125 to 250 pounds fertilizer N per acre (Moschler et al. 1967, Mitchell and Teel 1977, Ebelhar et al. 1984). The reason for the yield reduction is explained as a combination of the large N demand of corn, the necessity of early corn planting dates, and the tendency of hairy vetch to deplete soil moisture. This previous research suggests that new legislation mandating cover crop use in order to reduce soil erosion would have to allow supplemental fertilizer N use if Illinois corn farmers are to remain economically competitive.
Contrary to the published literature many Illinois farmers utilizing cover crops report that hairy vetch can, under the right conditions, produce in excess of 3001b of N per acre (Holsapple, 1990). The difference may be an artifact of improperly managed cover crops in the published literature. This proposed research will help to resolve some of these questions. Rye has been shown to be inferior generally to hairy vetch in the lower Corn Belt (Ebelhar et al. 1984), but environmental conditions and corn planting date requirements often result in vetch not establishing well and/or not producing a substantial biomass. We speculate that under such conditions rye, which is easier to establish and has greater early season growth, may prove to be comparable to hairy vetch for the purposes described above.
Corn is the major feed grain crop in Illinois and virtually all of the winter cover crop / summer feed grain crop rotation work in this area has looked only at corn, but corn is probably not the best feed grain crop for such a system. Grain sorghum (Sorghum bicolor L.) has a shorter grainfill period and thus can be planted later than corn without suffering a yield reduction (Olson et al. 1986). Grain sorghum also has a lower N requirement for optimum economic production than corn (80 pounds per acre vs 160 pounds per acre) (Olson et al. 1986) and thus may be a potential alternative summer feed grain. Especially on drought prone soil or if it is found that vetch must be allowed to grow relatively late into the spring in order to fix more organic N. Wagger (1987) reported that killing hairy vetch the first week of May instead of the third week of April resulted in an additional production of 1.78 tons dry matter per acre and 521bs N per acre. This is in agreement with Frye et al (1988) who noted that the majority of the vegetative growth of hairy vetch occurred in the three weeks prior to the onset of the reproductive stage.
The later planting date would result in more subsoil moisture depletion by the cover crop, but utilization of grain sorghum instead of corn would allow for a later planting date and thus permit a producer to wait longer for adequate soil moisture in the planting zone after the cover crop has been destroyed. Grain sorghum is also more drought tolerant than corn (Olson et al. 1986). Hargrove (1986) has demonstrated in Georgia a production system using winter legumes followed by grain sorghum is possible. Such a system has not been investigated in the central corn belt and farmers and scientists have little experience to predict the outcome of such a system.
Environment is a large factor in grain crop performance. When soils are deep and fertile and there is ample moisture, corn will produce more feed grain than grain sorghum. But if the soil is shallow, fertilizer inputs are reduced, or moisture is limiting, grain sorghum can yield as much or more feed grain than corn. For example, near Brownstown, Illinois the soils are relatively shallow, have low plant-available water holding capacity, and underlain with a dense acidic clay pan, and are thus very susceptible to drought. In the University of Illinois variety performance trials at Brownstown, grain sorghum often produces substantially more feed grain than corn. This relationship is seen commonly in much of the southern portions of Illinois. These areas also have longer growing seasons and have severe problems with soil erosion.
The question of tillage necessity in a cover crop system has not been answered. Some research has reported that the cover crop should be plowed under in order to enhance N mineralization (Varco 1986) while others report that it is equally effective if the winter cover crop is killed with a herbicide and then the following summer feed grain crop is no-till planted (Triplet et al 1979; Flannery 1981). The no-till system is attractive because it reduces soil erosion, uses much less fuel, and requires smaller tractors, but it does mandate the use of herbicides. Farmers in Illinois have shown that the plow system can be successful with limited or no herbicides (personal conversation with T. Holsapple, 1989).
The objectives of this field experiment are to address the long term effects
of cover crops on production efficiency, N requirement, environmental consequences,
and economic competitiveness of production systems for a summer feed grain /
soybean rotation. The goal of this research is to identify and demonstrate economically
competitive and environmentally sound production systems for Illinois.
This field experiment is a split-split-split-split plot in a randomized complete block design with three replications per location and three locations. The experiment is located at (from South to North) Tom Hortin's farm at Albion, IL; Terry Holsapple's farm Toledo, IL; and Mark Cender's farm at Fisher, IL. Whole plot treatments are tillage used the spring prior to feed grain planting: 1) no-till and 2) conventional. The split treatments are type of cover: 1) hairy vetch, 2) rye, and 3) conventional i.e. no planted cover. The split-split plot treatments are feed grain: 1) grain sorghum and 2) corn. The split-split-split plot treatments are feed grain planting date: 1) May 1 and 2) May 20. The split-split-split-split plot treatment are N fertilizer rate: 1) 0 lb N/ac, 2) 801b N/ac, 3) 160 lb N/ac, and 4) 240 lb N/ac. Individual plot size are 20 feet wide (8, 30 inch rows) by 65 feet long.
The feed grain part of this experiment was completed in 1993. The results were
published as Bollero and Bullock (1994). The covers and feed grains were not
planted for the 1994 season as explained in the proposal. Rather, in this last
year we were only interested in the residual effect of cover crops on soybean
grain yield in the following year. Weed pressure and technical problems prevented
our harvesting all plots at all locations. The analysis was conducted with missing
plot techniques.
Soybean Grain Yield
Plots which were in corn and grain sorghum in 1993 were bulk planted to soybean
in 1994. Analysis of variance of soybean yield from harvestable plots indicated
no significant differences due to any main effect or interaction. This is in
agreement with 1993, but contrary to 1992 in which soybean yield was affected
by the main effect of cover crop and the interactions of cover crop X date of
planting and tillage X feed grain crop (Bollero et al., 1992). Based on these
three years of data we conclude that cover crops such as hairy vetch and rye
do not have a consistent beneficial affect on soybean in a feed grain / soybean
rotation.
Bollero, G. A., D. G. Bullock, T. Bicki, R. Farnsworth, M. Cender, T. Holsapple and T. Hortin. 1993. Evaluation of nitrogen fertilizer rate, planting date, tillage and winter cover crops in a summer feed grain/soybean production system in central and southern Illinois. pp. 107-117. In Proc. Illinois Fertilizer Con£ Springfield, IL.
Boller, G.A. and D.G. Bullock. 1994. Cover cropping systems for the central corn belt. J. Prod. Agric. 7:55-58.
Ebelhar, S.A., W.W. Frye, and R.L. Blevins. 1984. Nitrogen from legume cover crops for notillage corn. Agron. J. 76:51-55.
Flannery, R.L. 1981. Conventional vs. no-tillage corn silage production. Better Crops 65:3-6 (Summer-Fall).
Frye, W.W., R.L. Blevins, M.S. Smith, S.J. Corak, and J.J. Varco. 1988. Role of annual legume cover crops in efficient use of water and nitrogen. p.. 129-154. In W.L. Hargrove (ed.) Cropping strategies for efficient use of water and nitrogen. ASA Spec. Publ. 51. ASA, CSSA, and SSSA, Madison, WI.
Hargrove, W.L. 1986. Winter legumes as a nitrogen source for no-till grain sorghum. Agron J. 78:70-74.
Heichel, G.H., and D.K. Barnes. 1984. Opportunities for meeting crop nitrogen needs from symbiotic nitrogen fixation. p.49-59. In D.A. Bezdicek et al. (ed.) Organic farming: Current technology and its role in a sustainable agriculture. Spec. Pub. 46. American Society of Agronomy, Madison, WI.
Holsapple, Terry. 1990. Fertilizer freedom. The New Farm. January. pp. 29-30.
Moschler, W.W., G.M. Shear, D.L. Hallock, R.D. Sears, and G.D. Jones. 1967. Winter cover crops for sod-planted corn: Their selection and management. Agron. J. 59:547-551.
Mitchell, W.H., and M.R. Teel. 1977. Winter-annual cover crops for no-tillage corn production. Agron. J. 69:569-573.
Olson, R.A., W.R. Raun, Yang Shou Chun, and J. Skopp. 1986. Nitrogen management and interseeding effects on irrigated corn and sorghum and on soil strength. Agron. J. 78:856-862.
Triplett, G.B. Jr., F. Haghiri, and D.M. Van Doren, Jr. 1979. Plowing effect on corn yield response to N following alfalfa. Agron J. 71:801-803.
Varco, J.J. 1986. Tillage effects on transformation of legume and fertilizer nitrogen and crop recovery residue nitrogen. Ph.D. diss. Univ. of Kentucky, Lexington (Diss. Abst. 8705310).
Wagger, M.G. 1987. Timing effects of cover crop desiccation on decomposition rates and subsequent nitrogen uptake by corn. p. 35-37. In J.F. Power (ed.) The role of legumes in conservation tillage systems. Soil Conserv. Soc. AM., Ankeny, IA.
