الفهرس 
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Abstract
The present study was conducted at of Faculty Agriculture, Saba Basha, Alexandria University, to study the use of chlorophyll meter to monitor nitrogen status and predicting nitrogen fertilizer requirements for corn grown under alkaline soil conditions. To achieve this goal, field studies were designed to test the chlorophyll meter for three corn varieties and two sources of N fertilizer (urea and ammonium nitrate).
Experimentation
Two field experiments were carried out during the year 2009(May-September). The area of the sub-plot was 10.50 m2 (3.5 m length x 3 m width), with 5 ridges 60 cm apart and 25 cm between hills. The first experiment was carried out for urea N fertilizer and the second for ammonium nitrate N fertilizer. Each experiment included 15 treatments which were the combination of five nitrogen rates, and three cultivars of corn (Zea mays).
The recommended dose of phosphorus (36 Kg P2O5) as superphosphate fertilizer was applied to the soil in a single dose during land preparation. Also, potassium (90 Kg K2O/fed) as potassium sulphate was applied to the soil in two doses equals. The first dose was on June. 27, 2009 and the second dose was on July. 11, 2009. Five nitrogen rates (25, 50, 75, 100, kg N/fed.) besides the control treatment (without nitrogen) of the two nitrogen sources (urea and ammonium nitrate) were used. The Nitrogen fertilizers were added in two equal doses. The first dose after three weeks from sowing and the second dose after two weeks from the first dose. The three corn cultivars of corn were sown on May 25, 2009. Other practices for corn growing were realized as recommended. Harvesting took place on September 22, 2009. Nitrogen reference plot that has been created by applying extra N (100 kg N/Fed) was established for each corn variety and N source to be tested. The Chlorophyll concentration meter (CCM-200) is a self-contained, handheld device powered by a 9V alkaline battery. The chlorophyll meter used to determine chlorophyll concentration index value that is proportional to the amount of chlorophyll in the sample obtained results can be summarized as follows: