GROWTH DYNAMICS AND LEAF CHARACTERISTICS IN OATS (AVENA SATIVA L.) DIFFER AT EXCESSIVE NITROGEN AND PHOSPHORUS APPLICATION

Abstract

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 (N2P2) 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.