Two field experiments were carried out at Itay El-Baroud Agricultural Research Station Farm-El Behira Governorate-Egypt during two successive winter seasons of 2016 /2017 and 2017/2018 to investigate the possibility of reducing nitrogen fertilizer rates by adding humic substance (Actosol ®) and their effects on growth, yield, yield components and some chemical properties of Serow 4 canola variety plants. The studied treatments consisted of seven different doses of recommended nitrogen (30 kg N / fed) with or without Actosol (6 liters / fed) as follows: 50 % nitrogen without Actosol (50 % N-Act.), 75 % nitrogen without Actosol (75 % N-Act.), 100 % nitrogen without Actosol (100 % N-Act.), zero nitrogen with Actosol (0 % N+Act.), 50 % nitrogen with Actosol (50 % N+Act.), 75 % nitrogen with Actosol (75 % N+Act.), and 100 % nitrogen with Actosol (100 % N+Act.). The experimental design was randomized complete block with three replicates. Results showed that decreasing nitrogen rates with or without humic substance (Actosol) linearly decreased plant height, number of branches and fruits/plant, 1000-seed weight, seed yield/plant, seed yield/fed and seed oil yield/fed, while it had increased, but non-significantly, seed oil content. However, application of Actosol increased all characters, except seed oil content where it had no significant effect on that trait at all studied nitrogen rates. Treatment of (75 % N+Act.) was better than (100 % N-Act.) for most studied characters. Therefore, nitrogen fertilization rate can be reduced by about 25% of the recommended by adding the recommended dose of Actosol (6 liters / fed).
A greenhouse experiment of maize (Pioneer P444) was conducted in Bader region, Behera governorate, Egypt to investigate the successive salinity application, irrigation level and potassium salt effects on maize germination and growth. Three levels of irrigation were included (80, 60 and 40 % of the potential evapotranspiration (ET)) as a main factor and four potassium salts (Control, K2SO4, KNO3 and Salwax) as a sub factor with three replications. Moderately salinity water (≈4 dS/m) was used. Germination of seeds and growth parameters of maize were monitored. A second-degree polynomial was implemented to describe some growth parameters. The results showed that the potassium salts did not affect the seed germination in comparison to the control. The polynomial well described the plant height and leaf number as a function of growth time with an approximated R 2 of 0.99. The plant height and leaf number increased as the irrigation level increased but the stem diameter behaved differently. The stem height and leaf growth rates decreased with time for all investigated treatments. The irrigation levels at 80 and 60 % ET quickly increased the soil salinity compared to that irrigated at 40 % ET. So, the plants that received irrigation water at 60 or 80 % ET levels were hampered after 56 days of growth. However, the plants irrigated at the 40 % ET level continued in growing till 108 days (harvesting time). The KNO3 was the best salt among other potassium salts types in boosting the maize growth in most of studied growth characters. Accordingly, the total water potential (matrtic and osmotic) is considered as a good criterion for defining drought maize tolerance.
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