Northern Great Plains Cropping Systems: Influences on Soil Properties
Associated with Soil Quality
Mark A. Liebig*, Sara Wright, Linda Jawson, Don L. Tanaka, Joe M. Krupinsky,
Steve D. Merrill, John R. Hendrickson, Randy L. Anderson, Ron E. Ries, and Jon D. Hanson
USDA-ARS, Mandan, ND, Beltsville, MD, and Brookings, SD
*
Corresponding author: liebigm@mandan.ars.usda.gov, (701) 667-3079The U.S. Department of Agriculture, Agricultural Research Service is an equal opportunity/affirmative action employer and all agency services are available without discrimination.
INTRODUCTION
The long-term sustainability of cropping systems is largely determined by their impact on soil quality. Because soil quality is directly related to the capacity of soil to function (Karlen et al., 1997), it envelops many aspects of cropping system performance. Measures of performance include biological productivity, erodibility, nutrient cycling efficiency, regulation of atmospheric gases, and mediation of water flows (Ericksen and McSweeney, 1999; Doran and Parkin, 1996; Karlen and Stott, 1994; Larson and Pierce, 1991). Off-site environmental problems caused by cropping systems are often linked to a compromised soil function resulting from poor soil management. Consequently, information on how cropping systems influence soil quality will allow agriculturists to design systems that are more environmentally sustainable (Karlen et al., 1994).
Decreasing commodity prices for cereal-base crops have resulted in greater crop diversification in the Northern Great Plains. Alternative crops in the region include canola, crambe, safflower, field pea, dry bean, soybean, chickpea, corn, millet, and buckwheat, just to name a few. The effects of these alternative crops on soil condition individually and in rotation are largely unknown. Understanding their effects on the soil resource is essential to develop sustainable cropping systems (Wienhold and Halvorson, 1998). Crop effects on near-surface properties, in particular, are vitally important given the impact the soil surface has on erosion control, water infiltration, and nutrient conservation (Franzluebbers, 2001).
The objective of this paper is to present an overview of crop sequence and cropping system effects on soil quality indicators in the Northern Great Plains.
SHORT-TERM EFFECTS OF CROP SEQUENCES
A short-term crop sequence experiment was established near Mandan, ND in 1998 on a Wilton silt loam (fine-silty, mixed, superactive frigid Pachic Haplustoll). The experiment consisted of 10 crops (barley, wheat, crambe, canola, sunflower, safflower, flax, dry pea, dry bean, and soybean) seeded into the residue of the same 10 crops under no-till management (Figure 1). The experiment used a strip-block design with four replicates. Experimental units were present two consecutive years. The experiment occupied approximately 34 acres, with individual plots 30 by 30 feet in size.
Figure 1. One matrix (replicate) used to evaluate short-term crop sequence effects under no-till management. As an example, plot 468 was planted to dry pea in 1998, and wheat in 1999.
To investigate short-term effects of individual crops on soil properties, soil samples were collected in the spring of 2000 and 2001 from plots where the same crop was previously planted in consecutive years (e.g., canola-canola, crambe-crambe, etc.). Samples were collected from two depths, 0-7.5 and 7.5-30 cm with a hand probe. Samples were analyzed for physical, chemical, and biological properties considered sensitive to short-term changes in management. Properties included wet aggregate stability, soil NO3-N, potentially mineralizable nitrogen, identifiable plant material (>2.0 mm), particulate organic matter (0.053-0.5 and 0.5-2.0 mm fractions), soil microbial biomass, and glomalin. Data were averaged over years and expressed on a volumetric, oven-dry basis. Mean values of soil properties as affected by crop were compared using a P-value of 0.1.
Soil properties influenced by crop in a short-term crop sequence experiment under no-till management near Mandan, ND. Data is for the 0-7.5 cm depth and specific to plots where the same crop was planted in consecutive years.
- - - - - 1-2 mm fraction - - - - -
Microbial Total Easily extractable
Soil NO3-N biomass C glomalin glomalin
Crop (kg ha-1) Soil pH (kg ha-1) (mg g-1) (mg g-1)
Spring wheat 6.4 6.18 514 3.41 0.57
Barley 5.6 6.00 472 4.22 0.75
Canola 5.9 6.13 619 3.38 0.64
Crambe 7.8 6.40 518 3.98 0.69
Flax 6.6 6.12 561 4.26 0.69
Sunflower 5.7 6.22 730 4.16 0.65
Safflower 5.1 6.10 439 4.12 0.69
Dry pea 10.1 5.88 396 3.63 0.61
Dry bean 6.5 6.04 486 3.35 0.63
Soybean 5.6 6.08 604 3.42 0.63
LSD (0.1) 2.3 0.24 177 0.62 0.05
LSD = Least significant difference. Numbers in a column differing by more than the LSD value are considered significantly different at P<0.1.Results from this experiment show:
Given the short-time frame of the experiment, few of the measured soil properties were affected by crop. This result underscores the importance of evaluating crops in long-term experiments to ensure trends in soil properties are constant and not ephemeral. Continuous cropping of some crops can lead to disease build-up in soil and significant weed pressure resulting in reduced crop yields. Consequently, crop effects on soil condition may be better evaluated in rotation.
While trends in a few soil properties were observed in this study, caution should be exercised when projecting crop effects over the long-term. This is especially true for properties affected by crop but not related to parameters known to affect agroecosystem functions (e.g., glomalin was affected by crop, but not correlated with aggregate stability).
LONG-TERM EFFECTS OF CROPPING SYSTEMS
A long-term cropping systems study was established near Mandan, ND in 1984 on a Wilton silt loam (fine-silty, mixed, superactive frigid Pachic Haplustoll). Management variables included in the study were crop sequence, tillage, and N fertilization. Each phase of both crop sequences occurred every year. Treatment combinations were replicated three times. The experiment occupied approximately 65 acres, with individual plots 80 by 150 feet in size.
The study was terminated in the fall of 2000. Soil samples were collected prior to field activities in spring 2001 from contrasting treatments [(spring wheat winter wheat sunflower, no-till, 60 lb N/ac) and (spring wheat fallow, conventional tillage, 20 lb N/ac)] to investigate cumulative management effects on soil properties (17 years). Samples were collected to 30 cm in increments of 0-7.5, 7.5-15, and 15-30 cm and analyzed for standard soil physical, chemical, and biological properties. In addition to laboratory assessments, infiltration rate was measured with single-ring infiltrometers at the time of sampling (Sarrantonio et al., 1996). As a contrast to the two cropping systems, samples were also collected from a nearby moderately grazed pasture with the same soil type (established in 1916 with 6.4 ac/steer for approximately 140 d/yr). All laboratory data were expressed on a volumetric, oven-dry basis. Mean values of soil properties as affected by cropping system were compared using a P-value of 0.05.
Soil properties as affected by management for a long-term cropping systems study near Mandan, ND. Data is for the 0-7.5 cm depth. Below 7.5 cm, few properties were affected by management, and are therefore not shown. As a contrast, properties in a grazed pasture with the same soil type are shown in the right column.
- - - - - - Cropping system - - - - - -
Soil property SW-F, CT SW-WW-SF, NT Grazed pasture
Soil bulk density (Mg m-3) 1.19 1.13 0.85
Wet aggregate stability,
1-2 mm fraction (%) 14 b 47 a 93
Infiltration rate (cm hr-1) 20.3 b 75.9 a 29.1
Electrical conductivity (dS m-1) 0.14 0.19 0.26
Soil pH (-log[H+]) 6.43 6.16 6.27
Soil properties as affected by management for a long-term cropping systems study near Mandan, ND. Contd.
- - - - - - Cropping system - - - - - -
Soil property SW-F, CT SW-WW-SF, NT Grazed pasture
Soil NO3-N (kg ha-1) 1.9 3.0 7.2
Potentially mineralizable
nitrogen (kg ha-1) 24.1 b 56.5 a 85.7
Soil organic carbon (C) (Mg ha-1) 16.42 b 23.70 a 31.56
Total nitrogen (N) (Mg ha-1) 1.63 b 2.24 a 2.55
Carbon in particulate organic
matter (Mg ha-1) 2.61 b 7.59 a 15.77
Nitrogen in particulate organic
matter (Mg ha-1) 0.21 b 0.54 a 1.04
Percentage (%) of soil organic C
as particulate organic matter C 16 b 32 a 50
Percentage (%) of total N
as particulate organic matter N 13 b 24 a 41
Microbial biomass C (kg ha-1) 424 b 1010 a 1598
Microbial biomass N (kg ha-1) 39 b 100 a 148
SW-F, CT = Spring wheat fallow, conventional tillage, 20 lb N ac-1 yr-1; SW-WW-SF, NT = Spring wheat winter wheat sunflower, no till, 60 lb N ac-1 yr-1.
Values within a row followed by a different letter are significantly different at P<0.05.Results from this experiment show:
Seventeen years of contrasting management resulted in distinctly different effects on soil condition. Based on the status of the soil properties measured, we can infer the continuous crop, no-till management system has a positive effect on the capacity of the soil to function with respect to its ability to provide a source for plant nutrients, withstand erosion, and facilitate water transfer into the soil relative to the crop-fallow, conventional tillage system. Management variables driving these changes in soil condition were 1) the greater amount of crop residue returned to the soil surface in the continuous crop system (Halvorson et al., 1999ab, 2000ab), 2) the greater amount of root biomass in no-till as compared to conventional tillage (Merrill et al., 1996), and 3) the slower rate of residue decomposition in no-till relative to conventional tillage (Wienhold and Halvorson, 1998). These results confirm that farmers in the Northern Great Plains can improve soil quality by adopting production systems that rely on intensive cropping practices with no-till management.
ACKOWLEDGMENTS
We thank John Bullinger for assistance with soil sampling. Gary Brucker, Jamie Erhardt, Nate Shilman, Nick Shilman, Becky Wald, and Alexa Zink provided technical support during sample processing and laboratory analyses.
REFERENCES
Doran, J.W., and T.B. Parkin. 1996. Quantitative indicators of soil quality: a minimum data set. p. 25-37. In J.W. Doran and A.J. Jones (ed.) Methods for assessing soil quality. SSSA Spec. Publ. 49. SSSA, Madison, WI.
Ericksen, P.J., and K. McSweeney. 1999. Fine-scale analysis of soil quality for various land uses and landforms in central Honduras. Am. J. Altern. Agric. 14(4):146-157.
Franzluebbers, A.J. 2001. Soil organic matter stratification ratio as an indicator of soil quality. Soil Tillage Res. (in press).
Halvorson, A.D., A.L. Black, J.M. Krupinsky, and S.D. Merrill. 1999. Dryland winter wheat response to tillage and nitrogen within an annual cropping system. Agron. J. 91:702-707.
Halvorson, A.D., A.L. Black, J.M. Krupinsky, S.D. Merrill, and D.L. Tanaka. 1999. Sunflower response to tillage and nitrogen fertilization under intensive cropping in a wheat rotation. Agron. J. 91:637-642.
Halvorson, A.D., A.L. Black, J.M. Krupinsky, S.D. Merrill, B.J. Wienhold, and D.L. Tanaka. 2000. Spring wheat response to tillage and nitrogen fertilization in rotation with sunflower and winter wheat. Agron. J. 92:136-144.
Halvorson, A.D., A.L. Black, J.M. Krupinsky, S.D. Merrill, B.J. Wienhold, and D.L. Tanaka. 2000. Spring wheat response to tillage system and nitrogen fertilization within a crop-fallow system. Agron. J. 92:288-294.
Karlen, D.L., and D.E. Stott. 1994. A framework for evaluating physical and chemical indicators of soil quality. p. 53-72. In J.W. Doran et al. (ed.) Defining soil quality for a sustainable environment. SSSA Spec. Publ. 35. SSSA, Madison, WI.
Karlen, D.L., G.E. Varvel, D.G. Bullock, and R.M. Cruse. 1994. Crop rotations for the 21st century. p. 1-45. In D.L. Sparks (ed.) Advances in Agronomy. Vol. 54. Academic Press, San Diego.
Karlen, D.L., M.J. Mausbach, J.W. Doran, R.G. Cline, R.F. Harris, and G.E. Shuman. 1997. Soil quality: A concept, definition, and framework for evaluation (A guest editorial). Soil Sci. Soc. Am. J. 61:4-10.
Larson, W.E., and F.J. Pierce. 1991. Conservation and enhancement of soil quality. In Evaluation for sustainable land management in the developing world. Vol. 2. IBSRAM Proc. 12(2). Bangkok, Thailand. Int. Board for Soil Res. and Management.
Merrill, S.D., A.L. Black, and A. Bauer. 1996. Conservation tillage affects root growth of dryland spring wheat under drought. Soil Sci. Soc. Am. J. 60:575-583.
Sarrantonio, M., J.W. Doran, M.A. Liebig, and J.J. Halvorson. 1996. On-farm assessment of soil quality and health. p. 83-105. In J.W. Doran and A.J. Jones (ed.) Methods for assessing soil quality. Soil Sci. Soc. Am. Spec. Publ. 49. SSSA, Madison, WI.
Wienhold, B.J., and A.D. Halvorson. 1998. Cropping system influences on several soil quality attributes in the northern Great Plains. J. Soil Water Conserv. 53(3):254-258.
Wright, S., and A. Upadhyaha. 1996. Extraction of an abundant and unusual protein from soil and comparison with hyphal protein of arbuscular mycorrhizal fungi. Soil Sci. 161(9): 575-586.