عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Boron toxicity is becoming more extensively widespread in arid and semi arid regions, due to the application of either saline waters or irrigation waters containing a relatively high B content. Results of research indicate that addition of certain plant nutrients such as N may reduce the harmful effect of high B levels. Therefore, the present experiment was undertaken to evaluate the interactive effect as of N and B on the growth and chemical composition of rice in a calcareous soil. Treatments consisted of six B rates ( 0, 2.5, 5, 10, 20 and 40 mg kg-1 as boric acid) and four levels of N ( 0, 75, 150 and 300 mg kg-1 as urea) arranged in a factorial manner in completely randomized design of three replicates.Application of B decreased shoot dry matter. In treatments with low B concentrations, N application alleviated the toxic effect of B. In the absence of B, application of 300 mgN kg-1 of soil caused an increase in dry matter weight by 55% as compared with control plants . Minimum of dry matter weight was in the absence of N with addition of 40 mg B kg-1 of soil (N0B40). Moreover, it was observed that the addition of B increases B and N concentrations in the aerial parts of the spinach plant. The N concentration increased while B accumulation decreased with increasing N rates. Application of N and B increased proline concentration in fresh leaf. Chlorophyll concentration decreased with increasing B levels. N fertilization increased chlorophyll content and somewhat reduced the adverse effects of high B rates on this plant parameter. There was a general trend of increase in chlorophyll concentration in fresh leaf with increasing chlorophyll meter readings. Application of B decreased mean Ca: B ratio in the spinach shoot, significantly due to B concentration getting increased with increasing B rates. But at all B levels, there was a general trend of increase in this ratio with application of N. The results reported herein show that in soils with high B levels, N application may alleviate the suppressing effects of B toxicity and increase rice growth, possibly due to a diminishing trend in B absorption by the plant.