Author
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Skinner, Robert |
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Submitted to: Crop Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/24/2007 Publication Date: 1/16/2008 Citation: Skinner, R.H. 2008. Yield, Root Growth and Soil Water Content of Drought-Stressed Pasture Mixtures Containing Chicory. Crop Science. 48:380-388. Interpretive Summary: Pastures in the northeastern USA frequently face periods of drought stress during the summer that can last for several weeks at a time. Creating pasture mixtures that include drought resistant species is one way to address this problem. Chicory (Cichorium intybus L.) is a deep-rooted forb that has increasingly been investigated for inclusion in pasture mixtures because of its reported drought tolerance and high productivity during summer months. In this study, 3-species grass-legume-chicory mixtures were compared with 2-species grass-legume mixtures under conditions where all rainfall and irrigation was excluded from field plots for two one-month periods each summer in 2003 and 2004. In 2003, drought stress reduced yield in the 2-species but not the 3-species mixtures compared to well-watered controls. The yield advantage of the 3-species mixture was related to greater water use efficiency rather than to greater access to soil moisture as one might expect with inclusion of the deep-rooted chicory. However, under drought stress, the 2-species mixture showed increased root proliferation in deeper soil layers and had more roots at depth than the mixture containing chicory. Chicory was not very persistent and had nearly disappeared from drought-stressed plots by the end of 2004. Thus, the yield advantage of the 3-species mixture was not observed in 2004. Including chicory in pasture mixtures can improve yield under drought stress. However, due to its short-lived nature, chicory will need to be reseeded on a regular basis to maintain the desired benefits. Technical Abstract: Chicory (Cichorium intybus L.) is a deep-rooted forb that has increasingly been investigated for inclusion in pasture mixtures because of its reported drought tolerance and high productivity during summer months. This study examined how adding chicory to pasture mixtures impacted forage yield, root growth and soil moisture extraction under drought-stressed conditions. Moveable rainout shelters were used to control water application in the field. Adding chicory to grass-legume mixtures decreased the susceptibility of the resulting 3-species mixtures to yield reductions due to drought stress in 2003 when chicory comprised 24 to 39% of harvested forage biomass. However, improved yield under drought stress was not observed in 2004 when chicory comprised only 9 to 16% of the mixture. The three-species mixture had greater root counts in deep soil layers than 2-species mixtures under well-watered conditions, but a greater proliferation of roots at depths below about 70 cm was observed for the 2-species mixture under drought stress. All mixtures appeared capable of nighttime transfer of soil water from deep to shallow soil layers, thereby improving water availability to shallow roots. However, because of the shallow nature of these soils this transfer did not appear to confer an additional measure of drought tolerance, primarily because all mixtures had access to water from the entire soil profile. Improved drought tolerance of the 3-species mixture appeared to be related to improved water use efficiency rather than to greater access to and extraction of deep soil moisture. |
