With regard to the low cation-exchange capacity and large saturated hydraulic conductivity of sandy soils, a field experiment was carried out in 2006–2007 to determine the impact of zeolite on nitrogen leaching and canola production. Four nitrogen (N) rates (0, 90, 180, and 270 kg ha^–1) and three zeolite amounts (3, 6 and 9 t ha⁻¹) were included as treatments. The results demonstrated that the highest growth parameters and seed yield were attained with 270 kg N ha⁻¹ and 9 t zeolite ha⁻¹. However, the highest and the lowest seed protein percentage and oil content were obtained with 270 kg N ha⁻¹ accompanied by 9 t zeolite ha⁻¹, respectively. Nitrate concentration in drained water was affected by nitrogen and zeolite. The lowest and highest leached nitrate values were found in control without N and zeolite (N₀Z₀) and in treatments with the highest N supply without zeolite (N₂₇₀Z₀), respectively. In general, nitrogen-use efficiency decreased with an increase in N supply. Application of 9 t zeolite ha⁻¹ showed higher nitrogen use efficiency than other zeolite amounts. Also, application of more N fertilizer in soil reduced nitrogen uptake efficiency. In total, application of 270 kg N ha⁻¹ and 9 t zeolite ha⁻¹ could be suggested as superior treatment.

To select and introduce the best rapeseed genotypes under withholding irrigation, two field experiments were carried out in seasons 2015–2016 and 2016–2017 in Iran. Factorial arrangement of treatments was set up as RCBD with three replications. The experiment factors were two irrigation treatments (normal irrigation during the growing season and withholding irrigation from silique setting stage until the end of the growing season) and 17 genotypes of rapeseed. Grain yield, oil content and fatty acid contents were measured. The results revealed that oleic acid (62.15%) was the highest followed by linoleic (19.28%), linolenic (5.65%), palmitic (5.24%) and stearic acids (2.44%). ODR (oleic desaturation ratio) and LDR (linoleic desaturation ratio) were significantly affected by genotypes and irrigation treatments. The biosynthetic pathway of fatty acids affected by drought stress. This means that linoleic acid increases under withholding irrigation condition, while linolenic acid decreases in such a water deficit stress condition. The highest performance of qualitative and quantitative was detected in HL3721 genotype due to high values of grain yield (3892.45 kg ha⁻¹), oil content (437.05 g kg⁻¹), unsaturated fatty acids (87.63%) and low values of saturated fatty acids (7.98%), and it could be used under withholding irrigation in arid and semi-arid climates.

Nitrate leaching from agricultural soils represents substantial losses of N from fertilizer. Nitrogen leaching in sandy soil decreases fertilizer efficiency and can depress crop production. Materials with high cation-exchange capacity are hypothesized to reduce N leaching and increase N uptake in sandy soils. This randomized complete-block design study evaluated the influence of chemical, organic, and integrated fertilizer treatments and natural zeolite on growth, yield, and grain mineral content of wheat (Triticum aestivum L.) grown on sandy soils. Supply of N by urea and composted cattle manure amended with 10% (w/w) zeolite increased wheat growth, yield, and yield components. Similar results were obtained when zeolite was applied directly to soil. The highest grain Zn, Fe, and Mn contents were achieved in plots treated only with organic fertilizers. Chemical plots produced the highest N and protein content. Integrated fertilizer treatments amended with zeolite are an effective and environmentally sound method to improve wheat yield.