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CROPPING SYSTEMS

Influence of Winter Cover Crop and Residue Management on Soil Nitrogen Availability and Corn

Washington State Univ., Puyallup Res. and Ext. Cent., 7612 Pioneer Way East, Puyallup, WA 98371-4998

* Corresponding author (skuo{at}wsu.edu)

Received for publication November 7, 2000.

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Removing cover crop top growth in the spring for forage or to prevent incorporation problems is one management option. The effects of this residue management on soil quality and productivity need to be determined. This study, conducted from 1994 to 1998 at Puyallup, WA, determined effects of various winter cover crops and residue management on soil N availability, soil C and N, and corn (Zea mays L.) yield. Included in the study were monocultures of rye (Secale cereale L.), ryegrass (Lolium multiflorum Lam), and vetch (Vicia villosa Roth subsp. villosa) and biculture of vetch and rye or ryegrass. Each year, the cover crops were seeded in the fall and incorporated into, or removed from, the soil in the spring. Average top-growth biomass was higher for the bicultures than for the monocultures. Total N accumulation was generally greatest under vetch, followed by the bicultures, and lowest for the monocultured rye or ryegrass. Whereas removing top growth of monocultured vetch or bicultures depressed presidedress soil NO₃–N (N_i), the effect was generally not found for monocultured rye or ryegrass. Corn yields were affected by amounts of N_i and N fertilizer applied (r² > 0.789), irrespective of cover crop species and residue management. Removing top growth of the cover crops limited residue C input and reduced soil organic C and N after 5 yr. Soil organic C and N accumulation, as well as increasing soil C sequestration to reduce CO₂ release into atmosphere, should be considered when deciding which residue management option to choose.

Abbreviations: N_f, amount of nitrogen fertilizer applied • N_i, amount of presidedress soil nitrate-nitrogen • N_t, total amount of nitrogen available to corn

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
IMPROVING SOIL N FERTILITY and protecting surface and/or ground water quality are often the two key objectives of establishing winter cover crops during the fallow season. The effectiveness of nonleguminous cover crops or mixture of leguminous and nonleguminous cover crops to reduce NO₃–N leaching is well recognized (Brandi-Dohrn et al., 1997; Owens, 1990). The effectiveness of various types of cover crops or combination of different cover crop species on soil N availability and the productivity of succeeding crops has been extensively evaluated (Holderbaum et al., 1990; Clark et al., 1997a; Kuo et al., 1996, Smith et al., 1987). It is quite clear from the literature that N content or C/N ratio of cover crop is a principal determinant of cover crop residue effects on soil N availability after residue incorporation into soil (Hargrove, 1986; Ranells and Wagger, 1996; Smith et al., 1987). Nonleguminous cover crops typically have low N contents and high C/N ratios, showing little or no beneficial effects on the succeeding crop yield in the short term. Including legumes as components in the cover crop is one avenue to increase N content of plant residue (Clark et al., 1997a; Ranells and Wagger, 1996). As plant tissue N increased or tissue C/N ratio decreased, the initial N mineralization potential and N mineralization rate increased (Frankenberger and Abdelmagid, 1985; Kuo and Sainju, 1998), and the crossover time for net N mineralization decreased (Kuo and Sainju, 1998).

Cover crop residues, however, could have some undesirable characteristics that may interfere with planting and growth of the succeeding crop. Among them are net N immobilization following incorporation of nonleguminous residue (Holderbaum et al., 1990; Wagger, 1989a, 1989b; Kuo and Sainju, 1998), allelopathy (Raimbault et al., 1990; Barnes and Putnam, 1986), or physical interference with corn seeding (Clark et al., 1997b). Managing cover crop residues before planting the succeeding crop is one important part of managing the whole production system, which deserves more attention. In the humid tropics, slash and burn is better than slash alone for the grain production and nutrient uptake of the succeeding rice (Oryza sativa L.) even though burning residue results in losses close to 90% of cover crop N and 85% of cover crop C (Luna-Orea and Wagger, 1996). Chemical control early in the spring can also be utilized to limit dry matter production of cover crops (Clark et al., 1997a). Reduced dry matter production of rye and, thereby, input into the soil by early spring kill increased soil N uptake and subsequent N mineralization (Brinsfield and Staver, 1991).

Removing cover crops for forage can be a management option for cover crop residue as well (Holderbaum et al., 1990). Legumes can be a potential source of quality forage (Taylor et al., 1982). Removing top growth of legume or rye cover crops may leave little, if any, effects on yield of succeeding corn or sorghum [Sorghum bicolor (L.) Moench] (Doll and Link, 1957; Raimbault et al., 1990). Even with a slight reduction in corn yield when the top growth of crimson clover (Trifolium incarnatum L.) was removed, the reduction was more than compensated for by the harvested crimson clover (Holderbaum et al., 1990). The total biomass yield under this residue management system was still higher than the total corn silage yield with the incorporation of the clover residue into the soil. In the rye cover crop and corn production system, the total biomass of harvested rye and corn exceeded the yield of monocrop corn with disk or moldboard plow tillage. The potential to remove the top growth of cover crops for forage provides flexibility in the overall forage production system.

Soil organic C and N are indexes of soil quality (Doran and Parkin, 1994). Their concentrations in soils are related to the total input of organic matter or crop residue (Rasmussen et al., 1980; Uhlen, 1991; Kuo et al., 1997a). Removal of cover crops by harvesting the top growth for forage will decrease the amount of organic matter input into soil and may adversely affect the soil accumulation of C and N over the long term. Increased C sequestration in soil is one avenue to reduce CO₂ concentration in the atmosphere. How residue management affects soil C, as well as soil N, needs to be assessed.

The objectives of this research were to determine: (i) the effect of winter cover crop with monocultured cereal rye, annual ryegrass, hairy vetch, or biculture of hairy vetch and rye or ryegrass and N fertilizer rate on corn yield; (ii) the effect of cover crop residue management consisting of soil incorporation or removal of the top growth on corn yield and N uptake; and (iii) the effect of residue management on soil organic C and N accumulation in the soil. Cover crop residue C and N concentrations and C and N inputs were among the factors considered in determining these effects under field conditions.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Cover crops included in this study were monocultures of hairy vetch (seeding rate, 28 kg ha^-1), annual ryegrass (28 kg ha^-1), and cereal rye (101 kg ha^-1) and bicultures of vetch and rye or ryegrass. The seeding rate for each species in the biculture was 70% of that used in the monoculture. From 1994 to 1998, the cover crops were planted to the same plots on a Sultan silt loam (fine-silty, mixed, mesic Aquantic Xerochrept) at a Washinton State University research farm near Puyallup, WA. The site has an average annual rainfall of 97 cm, 75% of which occurs from October to March, and an average annual temperature of 10.6°C. After the soil was tilled with a rototiller to a depth of about 10 cm, the cover crops were seeded with a row spacing of 19 cm. The fertilizers applied to the cover crop included K (56 kg K ha^-1 as KCl) and P (19 kg P ha^-1 as triple superphosphate). Potassium was broadcast before tillage and incorporated into soil, and P was banded with the cover crop seeds. The size of each plot was 9.1 by 36.6 m. Subplots for residue management, top growth incorporated or removed, were 9.1 by 18.3 m. Sub-subplots for N rate were 9.2 by 4.6 m. Each treatment was replicated three times using a randomized complete block design.

Aboveground biomass for the cover crops and the control without cover crops was determined about the last week of April each year by mowing a strip 2 by 5 to 9 m, depending on the cover crop, using a flail chopper. The plant material from each plot was subsampled for dry matter determination and total N analysis, and the remaining residue was returned to the plot. Immediately after sampling, the top growth of the cover crops and the control for the residue removal treatment was mowed with a flail chopper and removed from the plot. At the time of harvest, rye was in boot stage while the other cover crops were still in a vegetative stage. The vegetation in the control plot was primarily shepherd's-purse [Capsella bursa-pastoris (L.) Medikus].

Immediately after sampling, the experimental area was moldboard-plowed to a depth of about 20 cm and then rototilled to a depth of about 10 cm. Potassium (223 kg K ha^-1 as KCl) and S (11 kg ha^-1) were broadcast and incorporated into the soil. Corn (Pioneer ‘3845’) (91000 seeds ha^-1) was seeded to the plots about 2 wk after the cover crop incorporation. There were four N fertilizer application rates (0, 67, 134, and 201 kg N ha^-1). Zero or 67 kg N ha^-1 as ammonium nitrate (NH₄NO₃) was band-applied with 44 kg P as triple superphosphate at the time of seeding. Additional N fertilizer was sidedressed in mid-June for the 134 or 201 kg N ha^-1 treatment. Corn was harvested during the third or fourth week of September, depending on weather conditions, by cutting all of the plants in 3.2 m of a corn row in each plot. The plants were chopped using a forage chopper and subsamples were taken for the determination of dry matter yield, tissue N content, and N uptake.

Cover crop and corn subsamples were dried at 65°C for 72 h for determining moisture content. The plant materials were then ground to pass through a 1-mm sieve. Total N of the ground plant materials was analyzed by digestion in concentrated sulfuric acid (H₂SO₄) and hydrogen peroxide (H₂O₂) at 400°C, followed by steam distillation and titration (Keeney and Nelson, 1982).

Soil samples were taken from all plots before sidedressing to a depth of 30 cm in 15-cm increments from the midway between the corn rows of each plot every year except 1996. The soil samples were air-dried and crushed to pass a 2-mm sieve before analyzing for NO₃–N. The soils were extracted with 2 M KCl in a soil/solution ratio of 1:10, and then NH₄–N and NO₃–N were determined using an autoanalyzer. The concentration of NH₄–N was small (1–3 mg kg^-1) relative to NO₃–N concentration. The total organic C of the soil was determined by the Walkley and Black method (Nelson and Sommers, 1996). Organic N concentration of the soils was determined by the Kjeldahl method (Bremner and Mulvaney, 1982). In converting NO₃–N from mg kg^-1 to kg ha^-1, a soil bulk density of 1.32 g cm^-3 was assumed.

Analysis of variance was done using the Statistical Analysis System (SAS Inst., 1985). Mean separation was performed using Duncan's Multiple Range Test at the 5% probability level. Regression analysis was used to determine the relationship between corn growth parameters and soil N availability.

	RESULTS AND DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Cover Crop Nitrogen Concentrations and Accumulation
There was considerable variation in top-growth biomass and tissue N concentration (P < 0.001) among the cover crops (Table 1). In general, the bicultures tended to produce more top-growth biomass than respective monocultures presumably because of the higher seeding rate with the combination of vetch and rye or ryegrass (Sullivan et al., 1991). On average, top-growth biomass produced annually was 2.33, 2.15, 1.83, 1.40, 1.53, and 0.51 Mg ha^-1 for ryegrass–vetch, rye–vetch, vetch, ryegrass, rye, and shepherd's-purse, respectively. This represents forage production in addition to corn.

Transfer of fixed N from legumes to grasses has been considered to be one benefit of grass and legume bicultures (Ta and Faris, 1987). Increased N concentration of rye in biculture with vetch or clover lowered its C/N ratio from 40:1 to 28:1 (Ranells and Wagger, 1996) and reduced the N immobilization potential of the rye following its incorporation into soil. However, even with this improvement in N concentration, the net increase in N accumulation in the rye component was still very small, 4 kg N ha^-1 (Ranells and Wagger, 1996). In this regard, the growth and N uptake of the grass and legume was assumed to be independent, and top-growth biomass, tissue N concentration, and N uptake in the biculture system may be estimated using the growth parameters from the individual species grown in monoculture (Table 1). Averaged over the years, the estimated annual top-growth biomass was 2.34 and 2.38 Mg kg^-1 for rye–vetch and ryegrass–vetch, respectively, compared with the measured values of 2.18 and 2.53 Mg kg^-1. The estimates of tissue N concentration were 24.0 and 23.3 g kg^-1 for rye–vetch and ryegrass–vetch, respectively, comparable to the measured values of 23.2 and 23.2 g kg^-1 for rye–vetch and ryegrass–vetch, respectively. For N uptake, the estimates were 56.0 and 53.1 kg ha^-1 for rye–vetch and ryegrass–vetch, respectively, compared with 49.8 and 56.3 kg ha^-1 for rye–vetch and ryegrass–vetch, respectively. The estimates are close to the measured values for biomass, tissue N concentration, and N uptake, even with the simplification of assuming no interspecies interaction. The grass and vetch biculture may be unique as the grass provides an excellent support for vetch to grow upwards. This unique combination could have decreased the interspecies competition, making it feasible to estimate the growth and chemical composition of the bicultures from the individual species grown in monoculture. The usefulness of this result is that it may be feasible to manipulate the seeding rate of each species to obtain the desired residue growth and chemical composition, which can intimately affect the availability of its accumulated N if residue is incorporated into soil.

Effects of Cover Crops and Residue Management on Presidedress Soil Nitrate-Nitrogen Test
Release of mineralized N following degradation of incorporated cover crop residue depends on a variety of factors, including quantity of residue and tissue N concentration or C/N ratio. The C/N ratio critical to net N mineralization is close to 25 (Clark et al., 1997a; Kuo et al., 1997b). Given the considerable variation in tissue C/N ratio and the amount of the residue added to the soil among the cover crops (Table 1), it is not surprising that the amount of N mineralized after the residue incorporation varied substantially (Table 2). The amount of soil NO₃–N in 0- to 30-cm depth measured before N sidedressing in mid-June (or presidedress soil NO₃–N test) (N_i) reflects a quantity of soil-available N closely related to the crop productivity (Magdoff et al., 1984; Kuo et al., 1996). It reflects the overall effect of soil, residue, and environmental conditions (e.g., soil temperature and moisture) on soil N mineralization, unless extensive N leaching occurs.

Among management options for cover crop top growth are removal for forage or incorporation into soil. These residue management systems had differential effects on N_i, depending on type of cover crop. Removing top growth of monocultured vetch or bicultures tended to depress N_i, whereas such an effect was generally not found for monocultured rye or ryegrass (Table 2). Even with the removal of top growth, soil N_i was still increased by 10 to 22 kg N ha^-1 above the control for monocultured vetch (Table 2), apparently from root degradation. The increase was not as consistent for the biculture, which ranged from -26.4 kg N ha^-1 in 1994 to +17.4 in 1998 for rye–vetch and from -2.3 in 1997 to +16.2 in 1995 for ryegrass–vetch. Studies by Shipley et al. (1992) and Kuo et al. (1997b) had showed the amount of N accumulated in the root was 18 to 25%, 32%, and 8 to 10% of the total N accumulated in the top growth for rye, ryegrass, and vetch, respectively. The C/N ratio for vetch roots was 24 to 29 compared with 60 and above for rye or ryegrass (Kuo et al., 1997a), which may explain the tendency of vetch roots to increase N_i following degradation. These results are useful in selecting which residue management option to use. If increasing soil N availability and decreasing N fertilizer requirement are the main objectives of monocultured vetch or the bicultures, the top-growth residue should be left in place. For monocultured rye or ryegrass, the top growth can be either removed from the soil or left in place as either management practice had little effects on soil N availability. The results in Table 2, which show a wide variation in N_i among years, and cover crop and residue management treatments, also emphasize the importance of testing soils for the quantity of available N early in the growing season. The test is critical for developing a proper N fertilization program to increase N fertilizer use efficiency.

Corn yield and N uptake at zero N fertilizer addition responded to the cover crop treatments (Table 3). The response was unaffected by residue management so that average silage yield and N uptake across the residue management were used for comparing cover crop effects. In general, monocultured vetch produced the highest corn silage yield and N uptake, followed by the bicultures, and monocultured rye or ryegrass produced the least. As with N_i, corn yield and N uptake varied considerably with year within each cover crop treatment. Corn yield was highly correlated with N_i every year (r² ranged from 0.827–0.916), except for 1994 . This was true also for N uptake (r² ranged from 0.612–0.979).

View larger version (18K): [in this window] [in a new window]   Fig. 1. The relationship between total available N in the soil (Nt) early in the growing season and corn yields.

View larger version (19K): [in this window] [in a new window]   Fig. 2. The relationship between total available N in the soil (Nt) early in the growing season and N uptake.

Maximum corn yield calculated based on the regression equations (Table 4) was slightly higher following the residue incorporation than if the residue was removed in three out of four years. The averaged maximum yield over the four years was 20.32 ± 1.82 Mg ha^-1 SD for the residue incorporation and 19.96 ± 0.86 Mg ha^-1 SD for the residue removal. The average N_t to attain the maximum yield was lower for the residue removal (209.2 ± 32.4 kg N ha^-1 SD) than for the residue incorporation (242.6 ± 16.2 kg N ha^-1 SD). They agreed well with the estimates of 201 kg N ha^-1 for the residue removal and 232 for the residue incorporation treatment based on the relationship of relative yield and N_t (Fig. 3) . It is possible that a slightly higher maximum yield for the residue incorporation than for the residue removal may require a higher amount of N_t to attain it. The fertilizer requirement could be higher when the top growth of monocultured vetch or the bicultures is removed from the soil since the removal generally decreased N_i, as discussed earlier.

View larger version (22K): [in this window] [in a new window]   Fig. 3. The relationship between the total available N in the soil (Nt) early in the growing season and relative yield of corn.

View larger version (16K): [in this window] [in a new window]   Fig. 4. The effect of presidedress NO3-N on the corn yield response to the total available N (Nt) at a half of the Nt needed for maximum corn yield.

Concentrations of C and N in the surface soil (0 to 15-cm depth) increased with increasing total C input from the cover crops (Fig. 5) . In determining this relation, it was assumed that the average below ground biomass as percent of the top growth biomass determined by Kuo et al. (1997a) is applicable for this study and there was no species interaction. The average root biomass estimated was 53.9, 73.1, 34.0, 111.9% of the top growth biomass for rye, ryegrass, vetch and shepherd's-purse, respectively. One significant impact of the removal of the top growth of the cover crops over the five year period was the decreased soil C and N and lowered C:N ratio compared to the treatments in which the top growth was incorporated into the soil. The concentrations of C and N in the subsurface soil (15 to 30-cm depth) were unaffected (p > 0.05) by the total C input (data not included). Whereas the removal of the cover crop top growth for forage provides some economic incentive for the cover cropping system, it adversely affected the soil C and N concentrations in the surface soil.

View larger version (14K): [in this window] [in a new window]   Fig. 5. Organic C and N of the soil as affected by C input from cover crops.

	CONCLUSIONS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

The N_i, the amount of soil available N measured prior to sidedressing N fertilizer, was the primary factor affecting corn yield and N uptake, irrespective of the cover crop species or the residue management. Cover crops and residue management affected corn yield and N uptake through their influence on N_i. Whether or not top growth should be removed from the soil for forage depends mainly on the need for forage, but soil N fertility needs to be considered in the management decision. If increased soil N fertility or lowered N fertilizer need for maximum corn production is the primary consideration for the cover crops, top growth of monocultured vetch or the bicultures should be left in place as the removal of their top growth from the soil generally decreased N_i. Removal of top growth of monocultured rye or ryegrass is a viable option because incorporation or removal of the top growth had little effects on N_i.

A close correlation between C input and C and N concentrations in the surface soil was found. Removal of cover crop top growth lowered C input to the soil and led to a reduction in soil C and N concentrations, and soil C sequestration. Soil C and N are important indexes of soil quality. Enhancing soil quality, as well as increasing soil C sequestration and reducing CO₂ release from soil into atmosphere, should be considered in deciding which residue management option.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Scientific Paper no. 0050-32, Dep. of Crop and Soil Sci., College of Agric. and Home Econ. Res. Cent., Washington State Univ., Pullman, WA.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

• Barnes, J.P., and A.R. Putnam. 1986. Evidence for allelopathy by residues and aqueous extracts of rye (Secale cereale). Weed Sci. 34:384–390.
• Brandi-Dohrn, F.M., R.P. Dick, M. Hess, S.M. Kauffman, D.D. Hemphill, Jr., and J.S. Selker. 1997. Nitrate leaching under a cereal rye cover crop. J. Environ. Qual. 26:181–188.[Abstract/Free Full Text]
• Bremner, J.M., and C.S. Mulvaney. 1982. Total nitrogen. p. 595–625. In A.L. Page et al. (ed.) Methods of soil analysis, Part 2—Chemical and microbiological properties. 2nd ed. ASA and SSSA, Madison, WI.
• Brinsfield, R.B., and K.W. Staver. 1991. Use of cereal grain cover crops for reducing groundwater nitrate contamination in the Chesapeake Bay region. p. 79–82. In W.L. Hargrove (ed.) Cover crops for clean water. Soil Water Conserv. Soc., Ankeny, IA.
• Clark, A.J., A.M. Decker, J.J. Meisinger, and M.S. McIntosh. 1997a. Kill date of vetch, rye, and a vetch-rye mixture. I. Cover crop and corn nitrogen. Agron. J. 89:427–434.[Abstract/Free Full Text]
• Clark, A.J., A.M. Decker, J.J. Meisinger, and M.S. McIntosh. 1997b. Kill date of vetch, rye, and a vetch-rye mixture. II. Soil moisture and corn yield. Agron. J. 89:434–441.[Abstract/Free Full Text]
• Doll, E.C., and L.A. Link. 1957. Influence of various legumes on the yields of succeeding corn and wheat and nitrogen content of the soil. Agron. J. 49:307–309.[Abstract/Free Full Text]
• Doran, J.W., and T.B. Parkin. 1994. Defining assessing soil quality. p. 3–21. In J.W. Doran et al. (ed.) Defining soil quality for a sustainable environment. SSSA Spec. Publ. 35. ASA and SSSA, Madison, WI.
• Frankenberger, W.T., and H.M. Abdelmagid. 1985. Kinetic parameters of nitrogen mineralization rate of leguminous crops incorporated into soil. Plant Soil. 87:257–271.
• Hargrove, W.L. 1986. Winter legumes as a nitrogen source for no-till grain sorghum. Agron. J. 78:70–74.[Abstract/Free Full Text]
• Holderbaum, J.F., A.M. Decker, J.J. Meisinger, F.R. Mulford, and L.R. Vough. 1990. Harvest management of a crimson clover cover crop for no-till corn production. Agron. J. 82:918–923.[Abstract/Free Full Text]
• Keeney, D.R., and D.W. Nelson. 1982. Nitrogen—inorganic forms. p. 643–698. In A.L. Page et al. (ed.) Methods of soil analysis, Part 2—Chemical and microbiological properties, 2nd ed. ASA and SSSA, Madison, WI.
• Kuo, S., and U.M. Sainju. 1998. Nitrogen mineralization and availability of mixed leguminous and non-leguminous cover crop residues in soil. Biol. Fertil. Soils. 26:346–353.
• Kuo, S., U.M. Sainju, and E.J. Jellum. 1996. Winter cover cropping influence on nitrogen mineralization, presidedress soil nitrate test, and corn yields. Biol. Fertil. Soils. 22:310–317.
• Kuo, S., U.M. Sainju, and E.J. Jellum. 1997a. Winter cover crop effects on soil organic carbon and carbohydrate in soil. Soil Sci. Soc. Am. J. 61:145–152.[Abstract/Free Full Text]
• Kuo, S., U.M. Sainju, and E.J. Jellum. 1997b. Winter cover cropping influence on nitrogen in soil. Soil Sci. Soc. Am. J. 61:1392–1399.[Abstract/Free Full Text]
• Larson, W.E., C.E. Clapp, W.H. Pierre, and Y.B. Marachan. 1972 Effects of increasing amounts of organic residues on continuous corn: II. Organic carbon, nitrogen, phosphorus, and sulfur. Agron. J. 64:204–208.[Abstract/Free Full Text]
• Luna-Orea, P., and M.G. Wagger. 1996. Management of tropical legume cover crops in the Bolivian Amazon to sustain crop yields and soil productivity. Agron. J. 88:765–776.[Abstract/Free Full Text]
• Magdoff, F.R., D. Ross, and J. Amadon. 1984. A soil test for nitrogen availability to corn. Soil Sci. Soc. Am. J. 48:1301–1304.[Abstract/Free Full Text]
• McGill, W.B., and C.V. Cole. 1981. Comparative aspects of cycling of organic C, N, S, and P through soil organic matter. Geoderma 2:267–286.
• Nelson, D.W., and L.E. Sommers. 1996. Total carbon, organic carbon, and organic matter. p. 961–1010. In D.L. Sparks (ed.) Methods of soil analysis. Part 3. SSSA Book Series 5. SSSA and ASA, Madison, WI.
• Owens, L.B. 1990. Nitrate nitrogen concentrations in percolate from lysimeters planted to a legume-grass mixture. J. Environ. Qual. 19:131–135.[Abstract/Free Full Text]
• Raimbault, B.A., T.J. Vyn, and M. Tollenaae. 1990. Corn response to rye cover crop management and spring tillage systems. Agron. J. 82:1088–1093.[Abstract/Free Full Text]
• Ranells, N.N., and M.G. Wagger. 1996. Nitrogen release from grass and legume cover crop monocultures and bicultures. Agron. J. 88:777–782.[Abstract/Free Full Text]
• Rasmussen, P.E., R.R. Allmaras, C.R. Rohde, and N.C. Roger, Jr. 1980. Crop residue influences on soil nitrogen and carbon in a wheat-fallow system. Soil Sci. Soc. Am. J. 44:596–600.[Abstract/Free Full Text]
• SAS Institute. 1985. SAS user's guide: Statistics. 5th ed. SAS Inst., Cary, NC.
• Shipley, P.R., J.J. Meisinger, and A.M. Decker. 1992. Conserving residual corn fertilizer nitrogen with winter cover crops. Agron. J. 84:869–876.[Abstract/Free Full Text]
• Smith, M.S., W.W. Frye, and J.J. Varco. 1987. Legume winter cover crops. Adv. Soil Sci. 7:95–139.
• Sullivan, P.G., D.J. Parrish, and J.M. Luna. 1991. Cover crop contributions to N supply and water conservation in corn production. Am. J. Altern. Agric. 6:106–113.
• Ta, T.C., and M.S. Faris. 1987. Species variation in the fixation and transfer legumes to associated grasses. Plant Soil 98:265–274.
• Taylor, R.W., J.L. Griffin, and G.A. Meche. 1982. Yield and quality characteristics of vetch species for forage and cover crop. Univ. of Wisconsin–Madison Dep. of Agron. Prog. Rep. Clovers Spec. Purpose Legumes Res. 15:53–56.
• Torbert, H.A., D.W. Reeves, and R.L. Mulvaney. 1996. Winter legume cover crop benefits to corn: rotation vs. fixed-nitrogen effects. Agron. J. 88:527–535.[Abstract/Free Full Text]
• Uhlen, G. 1991. Long-term effects of fertilizer, manure, straw, and crop rotation on total N and C in soil. Acta Agric. Scand. 41:119–127.
• Wagger, M.G. 1989a. Time of desiccation effects on plant composition and subsequent nitrogen release from several winter annual cover crops. Agron. J. 81:236–241.[Abstract/Free Full Text]
• Wagger, M.G. 1989b. Cover crop management and nitrogen rate in relation to growth and yield of no-till corn. Agron. J. 81:533–538.[Abstract/Free Full Text]

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