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Globally, mineral nitrogen (N) losses as nitrate leaching (NL) are a substantial portion of applied fertilizer and cause surface and sub-surface water contamination. To precisely measure NL and its interlink parameters, biochar soil amendment was tested in this study. Three treatments—biochar (BC), without biochar (WB) with 15N urea (300 kg/ha), and control (no fertilization)—were tested in soil-filled lysimeters (circular PVC (Polyvinyl Chloride) tank of 30 cm diameter and 35 cm height) equipped with moisture content sensors and weighing assembly for the consecutive two cropping of Brassica Camprestis Var. Chinensis. The 15N-urea in the first season and the poultry manure in the second season were applied, but the fate of the 15N was examined in leachate, dry matter, and soil. As compared to WB, BC significantly decreased mineral N leaching, including nitrate levels (35%), increased electrical conductivity (68.5%), and water availability (20% inches per foot), while there was a non-significant increase in biomass per plant (2.84%), evapotranspiration (8.33%), dry matter (6.89%), and a decrease in mean leachate volume (7.63%). Moreover, BC accumulated values were higher than WB, as N uptake (38%), water use efficiency (12.24%), maximum fresh weight (11.4%), and soil N retained (185%) after cropping. The soil pH, the bulk density, and the total nitrogen were changed but presented non-significant differences. Therefore, biochar can increase soil N retention and available water to improve water use efficiency and decrease potential N leaching.

SUMMER savory (Satureja hortensis L.) plant is one of the most promising plants suitable for cultivation in the conditions of Egypt. A field experiment was carried out at Department of Ornamental Horticulture, Faculty of Agriculture, Cairo University, with Department of Medicinal and Aromatic Plants Research, National Research Center, Dokki, Giza, Egypt. during two successive seasons 2014 and 2015. The experimental design was a factorial in split plot with three replicates. The aim of the work was to study the effect of nitrogen fertilization at the rates of N0, N1, N2 and N3 (0, 40, 80 and 120 kg N/ feddan ) as equivalents 0.0, 200, 400 and 600 kg/feddan of ammonium sulfate fertilizer 20.5% N, respectively as the main plots. Plant spacing was defined as S1, S2 and S3 (45×50, 30×50 and 15×50 cm, respectively) between the plants, as sub-plots. The effect of these treatments on essential oil percentage, essential oil constituents and total flavonoid content of S. hortensis L. was recorded. The results showed that the highest level of N fertilizer to combined with the least plant spacing had a significant effect on increasing the essential oil percentages in both seasons. The major essential oil constituents were carvacrol (47.26 and 42.90%) and γ-terpinene (38.30 and 39.10%) at the first and second cuts, respectively. Generally, carvacrol content was not affected by N fertilizer, but the γ-terpinene content increased slightly. The other lower percentage components arranged in descending order including ρ-cymene, terpinolene, α-terpinene, α-pinene and α-thujene contents were not significantly affected by such treatments. Total flavonoid content decreased with all N fertilizer levels at the first cut (June), the opposite trend was noticed at the second cut (August) in both seasons. Plant spacing at intermediate density was associated with the production of high contents of total flavonoids at both cuts during both seasons.