Root distribution and nitrate interception in eleven temperate forage grasses

Abstract

Agrostis capillaris, Arrhenatherum elatius, Bromus willdenowii, Cynosurus cristatus, Dactylis glomerata, Elytrigia repens, Lolium multiflorum, L. perenne, Phalaris aquatica, Phleum pratense, Schedonorus phoenix, and a ryegrass selected for high surface root mass, were grown in 1 m deep · 90 mm diameter tubes of sand. Tubes were irrigated with a low ionic-strength nutrient solution and 15 N-labelled nitrate was leached down the tubes prior to harvest. Shoot weights, root weights in 10-cm depth increments, and shoot and root nitrogen concentrations were determined. Plants of L. multiflorum were the heaviest and plants of A. capillaris were the lightest. Root system shape was analysed by comparing the decay constant from an exponential model fitted to the proportion of root mass in 10-cm depth increments, and, also, by analysis of the proportion of root mass in the top 10 cm. Cynosurus cristatus was strongly surfacerooted and the perennial ryegrass, selected for high surface root mass, had more root mass between 0 and 10 cm than did the unselected perennial ryegrass cultivar. There were only small differences in root shape between the other grasses. There was a strong and positive correlation between plant dry weight and the proportion of the pulse of labelled nitrate that was intercepted. The variation in root system shape shown in this experiment had no effect on nitrate interception. Nitrate interception per unit root weight was significantly higher in A. capillaris than in the other grasses. Developing winter-active grasses that have finely divided root systems should contribute to pastures with better nitrate retention characteristics.

Phosphate uptake by white clover (Trifolium repensL.) genotypes with contrasting root morphology

“…This situation will be exacerbated if forage grasses with higher root length frequencies than are found in existing cultivars are introduced to alleviate nitrate leaching losses (Dunbabin et al 2003;Crush et al 2005a). Clovers with much higher root frequencies than those currently available will be required to offset the additional root competition, let alone allow a reduction in fertiliser P inputs.…”

“…Apart from the cost to farm budgets, the elevated soil P status is a risk factor for P losses (Monaghan et al 2007). The conceptual model grass root system for nitrate interception efficiency-high root length frequency from masses of fine roots (Dunbabm et al 2003;Crush et al 2005a), will exacerbate grass competition for P. Developing clovers with higher root length frequencies per unit volume of soil is one way of mitigating grass competition for P.…”

Leaf-Level Gas Exchange and Foliar Chemistry of Common Old-Field Species Responding to Warming and Precipitation Treatments

“…Elymus repens is a perennial, rhizomatous C 3 grass, and, in contrast to P. lanceolata and T. officinale, E. repens is not classified as a stress-958 tolerant species: it has a low drought tolerance and is considered to be shade intolerant (USDA 2010). Elymus repens also has a much deeper rooting depth, with a maximum rooting depth greater than 100 cm, although over 80% of the root mass is located at a depth of 0-30 cm (Crush et al 2005).…”

Nitrogen budgets of urban lawns under three different management regimes in southern California

“…In general, plant urease activities and root uptake of N and water can affect the magnitudes of NH 3 volatilization (Frankenberger and Tabatabai 1982), N leaching (Bowman et al 2002;Crush et al 2005), and denitrification (Virginia et al 1982). C 4 , warm-season turf species are known for low water requirements (Huang et al 1997;Youngner et al 1981).…”