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Abstract:Field experiments were conducted at Cereal Crops Research Institute, Pirsabak, Nowshera, Pakistan, during winter 2003~2004 and 2004~2005 to evaluate the effect of nitrogen and sulfur levels and methods of nitrogen application on canola (Brassica napus L. cv. Bulbul-98) under rainfed conditions. Four levels of S (0, 10, 20, and 30 kg/ha) and three levels of N (40, 60, and 80 kg/ha) and a control treatment with both nutrients at zero level were included in the experiments. Sulfur levels were applied at sowing while N levels were applied by three methods (100% soil application, 90% soil+10% foliar application, and 80% soil +20% foliar application). The experiments were laid out in randomized complete block (RCB) design having four replications. Oil content increased significantly up to 20 kg S/ha but further increase in S level did not enhance oil content. Glucosinolate content increased from 13.6 to 24.6 µmol/g as S rate was increased from 0 to 30 kg/ha. Protein content increased from 22.4% to 23.2% as S rate was increased from 0 to 20 kg/ha. Oil content responded negatively to the increasing N levels. The highest N level resulted in the highest values for protein (23.5%) and glucosinolate (19.9 µmol/g) contents. Methods of N application had no significant impact on any parameters under study.

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Arsenic (As), selenium (Se), and molybdenum (Mo) have become increasingly important in the terrestrial and agrobiological environment in some parts of the western USA. A four factorial [3 As × 3 Se × 2 Mo × 2 P concentrations] completely randomized glasshouse study was conducted to evaluate the competitive interactions between As(V), Se(VI), Mo(VI) and P using nutrient solution concentrations representative of soil solutions and agricultural drainage waters. Alfalfa [Medicago sativa L., Germain WL 512] was grown in sand culture and irrigated five times per day with half‐strength Hoagland's solution containing 0 (background), 0.05 and 0.10 mg L−1 As as Na2HAsO4; 0, 0.05, and 0.10 mg L−1 Se as Na2SeO4; and 0.01 (background) and 1.0 mg L−1 Mo as Na2MoO4. Instead of 16 mg L−1 P and 16 mg L−1 S commonly used in the half‐strength Hoagland solution, 1.0 or 4.0 mg L−1 P added as KH2PO4 and one somewhat lower level (8.0 mg L−1) S added as MgSO4 were used. The results indicated no adverse effect of As and Se on shoot yield. Selenium and P strongly depressed shoot As concentrations, and their combined effects were multiplicative rather than additive (significant Se × P interaction). Uptake of Se was decreased by increasing P, but was stimulated by increasing As, and the combined effects of P and As were approximately additive (non‐significant As × P interaction). Tissue concentrations of Mo and P were less dramatically influenced by solution concentrations of the other elements.