|NICHOLS, KRISTINE - Rodale Institute|
|TANAKA, DONALD - Retired ARS Employee|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2017
Publication Date: 2/8/2018
Citation: Liebig, M.A., Hendrickson, J.R., Franco Jr, J.G., Archer, D.W., Nichols, K.A., Tanaka, D.L. 2018. Near-surface soil property responses to forage production in a semiarid region. Soil Science Society of America Journal. 82:223-230. https://doi.org/10.2136/sssaj2017.07.0237.
Interpretive Summary: Understanding how perennial forages alter soil properties can contribute to the design and adoption of management practices that enhance ecosystem services from agricultural lands. This study sought to evaluate soil responses to perennial grasses, legumes, and grass-legume mixtures over a five year period at an experimental site near Mandan, North Dakota USA. Two hypotheses were postulated to guide the study: 1) the frequency of soil property differences between perennial forages and annual cropping would increase with time, and 2) a minimum of three years would be required to detect differences in soil properties among perennial forages. Relative to annual cropping, perennial forages mitigated soil acidification, reduced soil bulk density, and increased moderately-labile organic matter and aggregate stability. Contrasts between annual cropping and perennial forages suggested soil responses to the latter occur as soon as two years after forage establishment, but peak four years after establishment. Among perennial forages, intermediate wheatgrass in monoculture or mixed with alfalfa reduced soil bulk density and increased moderately-labile organic matter compared to alfalfa, but such differences took four to five years to be detected. Outcomes from the study suggested perennial forages maintained or improved near-surface soil conditions in a semiarid environment, but effects were subtle and changes to soil properties were slow to occur.
Technical Abstract: Integration of perennial plants in annual cropping systems can expand ecosystem service benefits to agricultural landscapes. Such benefits are frequently derived from changes to soil properties. Unfortunately, there is limited guidance for agricultural producers regarding the length of time needed to accrue soil condition improvements under perennial forages, particularly for semiarid regions. The objective of this study was to quantify soil responses to perennial grasses, legumes, and grass-legume mixtures over a five year period in a semiarid region. Select soil physical and chemical properties were measured within five perennial forage treatments and under annual cropping over a 5-yr period on a Parshall fine sandy loam near Mandan, ND USA. Treatment effects on soil properties were limited to the surface 10 cm. Differences in soil properties between spring wheat (Triticum aestivum L.) and perennial forages were most frequent following the fourth stand year. Compared to spring wheat, perennial forages mitigated soil acidification (by 0.26-0.65 pH units), reduced soil bulk density (by 0.04-0.08 Mg/m3), and increased particulate organic matter (by 0.41 g C/kg) and water-stable aggregates (by 3.8%). Among perennial forages, intermediate wheatgrass (Thinopyrum intermedium L.) and intermediate wheatgrass + pea/alfalfa (Pisum sativum L.; Medicago spp.) reduced soil bulk density (0.06-0.11 Mg/m3) and increased particulate organic matter (by 0.24-0.92 g C/kg) compared to alfalfa following four and five years of perennial forage stands. While outcomes from this study suggest perennial forages can maintain or improve near-surface soil condition, accrual of improvements will take considerable time in semiarid regions.