Submitted to: Renewable Agriculture and Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2005
Publication Date: 3/1/2006
Citation: Pikul Jr, J.L., Schwartz, R.C., Benjamin, J.G., Baumhardt, R.L., Merrill, S.D. 2006. Cropping systems influences on soil physical properties in the great plains. Renewable Agriculture and Food System. 21(1):15-25. Interpretive Summary: The state of the soil physical environment is important for maintaining sustained agronomic production, a concept embodied in the presumption that good soil tilth is a precursor to high crop productivity. Agricultural systems may produce both damaging and beneficial effects on soil physical condition. Little is known about the long-term interaction of crop systems, residue and fertilizer management on soil physical condition. Soil organic matter is linked to fertility and a desirable soil physical state and often has a disproportionate effect on soil physical behavior. Maintenance of soil organic matter seems to be the key to sustaining the soil resource and crop productivity. A multi-location study was conducted during 1999 to 2002 to evaluate a number of physical, chemical, and biological properties associated with assessment of soil quality. The purpose of this report is to present findings on selected soil physical attributes. We identified no significant cropping system effect on water infiltration for locations having the same tillage operations within the cropping system. Mean weight diameter of soil aggregates (an index of soil aggregate stability) was affected by cropping intensity and tillage. Systems without fallow or systems with reduced tillage had a larger mean weight diameter than systems having fallow or tillage. Tillage resulted in increased, decreased, or unchanged BD near the soil surface, when compared with no tillage, depending on time of year. Measurements of infiltration, mean weight diameter, or soil bulk density made at only one time in a rotation cycle do not convey meaningful information on soil quality because of significant temporal variation in these properties.
Technical Abstract: Agricultural systems produce both detrimental and beneficial effects on soil quality (SQ). We compared soil physical properties of long-term conventional (CON) and alternative (ALT) cropping systems near Akron, CO; Brookings, SD; Bushland, TX; Fargo, ND; Mandan, ND; Mead, NE; Sidney, MT; and Swift Current, SK. Objectives were to quantify temporal dynamics of soil physical attributes in cropping systems and assess the value of individual SQ attributes. Soil samples were collected three times per year per treatment for one rotation cycle (four years at Brookings and Mead). Water infiltration rates were measured. Soil bulk density (BD) and gravimetric water (GW) were measured at 0 to 75, 75 to 150 and 150 to 300 mm depth increments and water filled pore space (WFPS) was calculated. We used a WFPS ratio of 0.6 as soil-aeration-threshold (SAT) and evaluated distribution functions for the probability of exceeding a critical WFPS with time, treatment, or depth. A rotary sieve was used to separate soil (top 50mm) into six aggregate size groups. Mean weight diameter (MWD) of dry aggregates was calculated. Dry aggregate distribution (DASD) shows promise as an indicator of SQ related to susceptibility of soil to wind erosion. Aggregates from CON were least stable in water. Soil C was greater under ALT than CON for both Brookings and Mead. There was no crop system effect on water infiltration rates for locations having the same tillage within cropping system. Elevated WFPS at Fargo, Brookings, and Mead may have resulted in anaerobic soil conditions during a portion of the year. There was significant temporal variation in SQ attributes, and conclusions based on a single point-in-time observation should be avoided. Repeated measurements of WFPS or DASD reveal important temporal characteristics of SQ that could be used to judge soil condition as affected by management.