Growth dynamics and leaf characteristics in oats (Avena sativa L.) differ at excessive nitrogen and phosphorus application

Shoot-root ratio (by length),number of roots plant-1 (nrpp),number of tillers plant-1 (ntpp),and leaf characteristics [number of leaves plant-1 (nlpp),leaf length (ll),mean single leaf area (msla),leaf area plant-1 (lapp),leaf elongation rate (ler),leaf area index (lai),specific leaf area (sla),specific leaf weight (slw),and leaf area ratio (lar)] response of oats (avena sativa l.,cv. walker) was investigated under excessive nitrogen (n) as 200 mg n kg-1 (n1p0),excessive phosphorus (p) as 200 mg p kg-1 (n0p1),and combine 100 mg n + 100 mg p kg-1 of potting mix (n2p22) and control (n0p0) as check in pot experiment at dryland agriculture institute,west texas a&m university,canyon,texas,usa during winter 2009-10. the experiment was performed in completely randomized design (crd) with three replicates. shoot-root ratio increased with excessive n,excessive p and combined n + p applications due to the decline in root lengths. the lower shoot-root ratio in control was mainly attributed to the longer roots produced by oats. phosphorus alone or combined application with n (n2p2) increased nrpp over control. at the early stages,control had more nrpp than n alone. with advancement in crop growth,combined n + p applications had more favorable effects on ntpp than other treatments. excessive p had more but excessive n had less ntpp than control. except slw,all other parameters viz. nlpp,ll,ler,msla,lapp,lai,sla,and lar decreased due the toxic effects of excessive n. excessive p alone or combined n + p applications had beneficial effects on various leaf characteristics of oats viz. nlpp,ll,ler,msla,lapp,lai,sla,and lar.