جستجوی مقالات مرتبط با کلیدواژه « کلروفیل برگ » در نشریات گروه « آب و خاک »

In order to determine the nitrogen requirement of rice (cv. Guilaneh) using the nitrogen nutrition index and chlorophyll meter, an experiment was conducted as a randomized complete block design with three replications in the research field of the Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran in 2016. Experimental treatments consisted of six nitrogen fertilizer levels (0, 60, 120, 180, 240, and 300 kg N. ha-1; Urea source). Evaluation of the relationship between nitrogen nutrition index and chlorophyll-meter readings at three stages of plant growth (maximum tillering, booting, and heading) to predict grain yield in response to nitrogen fertilizer showed that the equation of the critical nitrogen concentration in Guilaneh was Nc = 3.99W -0.36. The correlation between chlorophyll-meter readings and nitrogen nutrition index was positive and significant at each plant growth stage. The results showed that the mature lower leaves were more sensitive than the younger higher leaves in response to nitrogen fertilizer and were more suitable for detecting plant nitrogen status, especially during the booting and heading stages. The highest correlation was found between the nitrogen nutrition index and chlorophyll-meter (r=0.95*) and relative chlorophyll-meter (the ratio of chlorophyll-meter readings in each treatment to nitrogen saturated treatment) (r=0.96**) in the third leaf and booting stage. The overall results of this experiment showed that the nitrogen nutrition index and chlorophyll meter may consider reliable indicators for evaluating the nitrogen status of rice (cv. Guilaneh) during the growing season.

Todays in agriculture, the effective use of limited soil and water resources and cultivation of new crops, resistant to environmental challenges, such as quinoa have been considered. In order to investigate the interaction effect of different levels of irrigation water and nitrogen fertilizer on yield and yield components of quinoa (cv. Titicaca), a field experiment was conducted on March 2017 during four months at Shiraz University in the Bajgah area of Fars province. A factorial experiment was conducted in a randomized complete block design with twelve treatments and three replications. Experimental Factors include: Nitrogen (N) fertilizer treatments in four levels of zero, 125, 250, 375 kg N ha-1 and the irrigation water strategies in three levels of full irrigation (FI), 75% and 50% full irrigation (0.75FI and 0.5FI. After tillage operations, quinoa seeds planted with a density of 20 plants per square meter. After plant establishment, irrigation treatments applied with basin irrigation method. Nitrogen fertilizer was given to the field in two steps of vegetation and grain filling.). Reduction Irrigation level up to 25% had no significant effect on seed yield in zero, 125 to 250 kg N ha-1 nitrogen fertilizer application levels. Increasing nitrogen fertilizer application levels from 250 to 375 kg N ha-1 under deficit irrigation (0.75FI and 0.5FI) did not make a significant difference in grain yield and the total dry matter of quinoa. Generally, the recommended irrigation regime and optimum nitrogen fertilizer application rate in the study area (Bajgah) for quinoa, based on the yield, total dry matter, harvest index, 1000-seed weight, water productivity were 0.75FI and 250 kg N ha-1 nitrogen fertilizer. Moreover, the chlorophyll index (SPAD) threshold value was 55 for the optimum nitrogen fertilizer application rate.

The application of biochar in the soil in order to improve soil quality and also waste management, has received considerable interest in recent years. Success of such management requires expert knowledge about the impact of a given biochar on soil and plant properties, before its field application. For this purpose, the effect of five different levels of biochar (0, 1, 2, 3 and 5% w/w), produced from residual of pistachio, on growth and water productivity of maize plants in a sandy and a silt loam soil was investigated. The study was performed in 2018 as a greenhouse experiment with a completely randomized design. The results showed that the effect of biochar on plant growth is strongly soil dependent. The biochar application had a negative effect on the growth of maize in the sandy soil. Root and shoot dry biomass as well water productivity were reduced more than 90% by application of 2 and 3% of biochar as compared to the control (0%), and the plant growth was hindered by further increase of biochar (at 5%). Consequently, water productivity was also reduced significantly. This negative effect of biochar application in sandy soil was attributed to an induced salinity as a result of biochar application and the low water holding capacity of the soil. In contrast, the effect of biochar on salinity of silty loam soil was not remarkable and only at application rate of 5%, it was increased significantly as compared to the control. Although the application of biochar in silty loam soil did not show a significant effect on root biomass, plant height, and chlorophyl index but shoot biomass and water productivity were increased till the application rate of 2% compared to the control. In conclusion, the results showed that i) one should be cautious with application of biochar (originated from pistachio residual) in coarse-textured soils, ii) and also the efficient application rate of each biochar should be determined in each soil before its application.

Nitrogen fertilizer application for corn (Zea mays L.) based on available N of soil can decrease the need to N fertilizer and, consequently, reduce the risk of environmental pollution, especially that of groundwater and drinking water. The objectives of this study were i) determining soil N03-N critical level at 4 to 6 leaf stage, ii) to study soil nitrate distribution, iii) determining N rate required for maximum corn grain yield, iv) measuring soil residual nitrate nitrogen after harvesting, and v) using hand chlorophyll meter to evaluate N status of corn. The experiment was conducted under field conditions in Bajgah and Kooshkak research stations (Fars Province) in 1996 using a split plot randomized complete block design with four replications. Main plots were control, 60, 120, and 180 kg N ha-1 as urea. At 4 to 6 leaf stage each main plot was divided into two sub-plots and N was applied at 60 kg N ha-1 rate to one sub-plot and the other sub-plot was left as control. Results showed that critical soil N03-N level at 4 to 6 leaf stage in 0-30 cm depth for 90 percent relative yield in Bajgah was 12-14 and for Kooshkak was 8-10 mg kg-1 soil. The highest coefficient of determination between corn grain yield and soil N03-N in 0-30 cm depth for Bajgah was in furrow sample and for Kooshkak was in furrow and shoulder composite sample. In both sites, maximum corn grain yield, with 15.5% moisture content, was about 14 mg ha-1 that was obtained through the application of 120 kg N ha-1 as preplant plus 60 kg N ha-1 as sidedress which is about 1/2 of the application rate used by local farmers. The highest residual soil N03-N after harvesting was 24 and 18 and the lowest was 2.6 and 3 mg kg-1 soil for Bajgah and Kooshkak soils, respectively. When maximum corn grain yield was obtained, chlorophyll meter reading at the middle of leaf blade at dough stage, was 49 for both sites. It seems that N fertilizer application rate by local farmers is excessive.