Light response of barley (Hordeum vulgare L.) and corn (Zea mays L.) as affected by drought stress, plant genotype and N fertilization

- Investigating sunlight interception by crop canopy affecting different crop parameters.
- Hypothesizing that the light response of field barley and corn, is affected by genetic (crop species) and environment.
- Effects of drought stress, crop genotype and nitrogen (N) fertilization on barley and maize growth and light response.
- The genotypes Nosrat (k=0.4624) and Yusef (k=0.4763) were the most efficient barley genotypes under drought.
- Light extinction coefficient (k) is a suitable indictor of canopy response to crop and environmental parameters.

It is important to investigate sun light interception by plant canopy as it affects different crop activities, most importantly the photosynthesis process and hence biomass production. It was hypothesized that the light response of barley and corn, is affected by genetic (crop species) and environmental conditions. Accordingly, field experiments were conducted to evaluate the effects of drought stress, crop genotype and nitrogen (N) fertilization on barley and silage maize growth and yield. The experiments were split plot on the basis of completely randomized block design in three replicates. In the barley experiment, the drought levels (70, 90 and 110 mm evaporation from the pan, class A) and the barley genotypes were devoted to the main and sub plots, respectively. In the silage maize experiment the N fertilization rates and maize genotypes were used as the main and sub plots, respectively. Different crop parameters including leaf area index (LAI), plant dry matter, light absorption, and silage and grain yield were determined for both barley and maize. Using the Beer-Lambert Law, the light extinction coefficients (k) were calculated. Although the highest level of k by barley genotypes was resulted at the control level of stress (0.4797), the corresponding values were not different at the medium and high level of stress (0.3958 and 0.3931, respectively). Drought significantly affected the grain yield of barley and resulted in a 16%, 15% and 6% decrease in plant dry matter, LAI and light absorption, respectively. The effects of genotype were significant on all determined parameters, and the interaction of genotype and stress was significant on light absorption and grain yield. The genotypes Nosrat (k=0.4624) and Yusef (k=0.4763) were the most efficient barley genotypes when grown under drought stress with respect to growth and yield parameters determined in the experiment. Although the effect of N fertilization was not significant on the rate of light absorption, the interaction of genotype and N fertilization significantly affected maize light absorption. The most efficient rate of N fertilization for maize silage and grain yield production was 100 kg/ha with respect to the rate of light intercepted (k=0.5113). The dry matter of silage maize was in the range of 1837-2535 g/m2. The interception of light and the other determined parameters for genotype 704 indicated that among different genotypes, it was the most efficient genotype. The growth and yield of both barley and maize were positively related with the light extinction coefficients. The results indicate that determination of light extinction coefficients is a suitable indictor of canopy response to different crop and environment parameters, and accordingly can be used for designing more efficient canopies with a higher rate of biomass and yield production.