عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Background and objectives: Monitoring nitrogen nutrition index (NNI) during the growing season can lead to improve fertilization management which will cause less damage for environment and water resources. The critical nitrogen concentration in plants can be obtained by critical nitrogen equations. Since determination of these equations is time consuming and costly, the equations which were proposed in other region have being usually used. But the results of the former studies have proved that climate variation, plant varieties and different agricultural managements can cause changes in these equations for new conditions. The main objective of this study was to verify and compare two nitrogen critical equations proposed in France and China, in order to estimate the NNI for maize in the region of Pakdasht.
Materials and methods: Hence, maize (single cross 704) for a season was planted at the farm of Aburaihan College. Treatments set during the growing season based on different nitrogen levels, from low to high, and samples of plant were taken to measure dry matter (W) and the concentration of nitrogen in the plant (% N). They included seven different levels of nitrogen as control (N0), 50(N1), 100(N2), 150 (N3), 200(N4), 250 (N5) And 300 kg of nitrogen per hectare (N6) by urea (containing 46% nitrogen) and were designed by randomized complete blocks in three repetitions. In order to verify these critical nitrogen equations, the method which was proposed by Planet and Limaire (2000) was used. Eventually, for investigating the impact of each equation in estimating NNI, the variation range of calculated NNI and its relation with relative grain yield were obtained and compare with other results.
Result: Generally, the results indicated the nitrogen critical equation which proposed in China was more compatible for Pakdasht region. The nitrogen status of the 14% data was overestimated by Chinese equation while nitrogen status of 21% data was estimated wrongly by the equation proposed for France. The less ranges of calculated NNI based on Chinese equation is other reason that show it’s rather accuracy in Pakdasht. Also by calculating NNI based on both equations, during growing season, it was demonstrated periods when treatments were encountered a lack of nitrogen. Finally it was indicated while calculating NNI based on both equation, during growing season, becomes less than 1.11, relative grain yield will decline.
Conclusions: Generally results indicates that the proposed critical nitrogen equation in China was better tools for diagnosing maize nitrogen status in Pakdasht because of the similarity in climate condition. In addition the NNI based on Chinese equation was more compatible for maize (single cross) in Pakdasht climate. However, both equation had more errors in pakdasht than region for where was developed.