Effects of irrigation and nitrogen fertilization on photosynthesis, leaf area index and dry matter production of wheat on a clay terrace soil of Bangladesh

A field research was conducted at the university farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh, during November 1997 t o March 1998 in order to study the effects of irrigation and nitrogen ferti lization on the leaf photosynthesis, leaf area index and dry matter product ion of wheat. The experiment was executed in the split-plot design comprisi ng the combination of the five levels of irrigation arranged as a main plot and the four rates of N application distributed to a sub-plot. The five ir rigation treatments were: I-o-no irrigation after the establishment of seed lings; I-1,-one irrigation at 23 days after sowing (DAS) of wheat seeds; I- 2-two irrigations: one at 23 DAS and the other at 60 DAS; I-3-two irrigatio ns: one at 23 DAS and the other at 80 DAS; l,three irrigations: at 23, 60 a nd 80 DAS. The four rates of N application were: N,no application of N fert ilizer; N,, N.. and N,application of N at the rates of 80, 120 and 160 kg h a (1), respectively. Both irrigation and N application have created a signi ficant impact on leaf photosynthesis (LPn), leaf area index (LAI), crop gro wth rate (CGR) and biomass production of wheat. Irrigation scheduling which included irrigation at the grain filling stage (80 DAS) coupled with N app lication up to 120 kg ha(-1) significantly increased LPn, LAI, CGR and biom ass production. With respect to the growth stage, LPn and CGR were highest at the anthesis stage (70-75DAS) and LAI was maximum at the booting stage ( 60DAS). Increased dry matter accumulation at maturation was mainly due to t he increased weight of grains.