Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2011
Publication Date: 7/5/2013
Citation: Zobel, R.W., Cassida, K.A., Kinraide, T.B., Gonzalez, J.L., Foster, J.G. 2013. Morphological response of forage chicory fine roots to manipulated soil phosphorus levels. Journal of Plant Nutrition. 36:1901-1914. Interpretive Summary: Plant growth on marginal soils is plagued with mineral and environmental stresses. Appalachian pastures frequently utilize the marginal soils of the region. Chicory, grown within pastures, can provide improved phosphorus uptake, but the mechanism is unknown. This manuscript identifies several of the mechanisms by which chicory cultivars adapt to soils with different levels of phosphorus. The authors demonstrate that the actual mechanism employed by chicory is dependent on cultivar, phosphorus level, and soil. They conclude that testing for these mechanisms in the laboratory may facilitate selecting cultivars for specific sites. This preselection will ultimately boost yields on marginal soils, and allow profitable cropping on soils currently unusable for agriculture.
Technical Abstract: Appalachian pastures suffer multiple stresses that result in reduced yields. Chicory offers the potential for increased phosphorus uptake, reduced drought stress and anthelmintic secondary products. To study the mechanism of improved phosphorus uptake, an experiment with three cultivars, two Appalachian soils and three or four phosphorus levels was undertaken. Forty-nine days after planting, roots were washed to collect organic acids from the rhizosphere, then measured for length and diameter. Two cultivars ‘INIA le Lacerta’ and ‘Grasslands Puna’ shifted total root length towards the thinnest roots, and ‘Grasslands Puna’ decreased the average diameter of the thinnest roots with decreasing phosphorus concentration. The third cultivar ‘Forage Feast’ responded with the opposite pattern. The two soils conditioned distinctly different plant and root growth responses, as well as organic acid production. The West Virginia soil “Gilpin” strongly suppressed plant and root growth at all P concentrations while increased P levels stimulated increased growth at all concentrations. The Pennsylvania soil “Harrisburg” conditioned good growth with little difference between P levels, indicating that it had adequate P levels prior to application of additional P. Only Gilpin soil-grown-roots of Forage Feast and Grasslands Puna (at the lowest P level) demonstrated increases in Malonic acid (plant exudation). Gilpin soil had higher levels of Formic acid (fungal activity), and Harrisburg soils had higher levels of Acetic acid (bacterial activity) across cultivars and P levels. It can be concluded that assessments of methods of plant adjustments (adaptations) to P levels must take into account differences between multiple soils, cultivars, and potential morphological & physiological mechanisms.