Lakhasly

1. Experimental design and agricultural practices
A field experiment was conducted in saline-sodic soil in the North Nile Delta of Egypt (Elserw district; 31◦ 15′ N, 32◦ 6′ E) during two growing seasons (2017–2018 and 2018–2019) to explore the combined effects of inorganic and organic soil amendments (i.e. sulfuric acid, gypsum and vermicompost) and tillage systems (i.e. zero, reduced and deep tillage) on soil physical and chemical characteristics, crop growth and yield of a new high yielding bread wheat cultivar (Triticum aestivum L., cv Misr 2).
The design of the experiment was a strip plot in four replications. Tillage systems (i.e. ZT, RT and DT) were placed in horizontal plots, while soil amendments (i.e. control, vermicompost, sulfuric acid and gypsum) were placed in vertical plots. The area of each sub plot was 50 m2 (5 m × 10 m). The RT included rotary tiller at 0–15 cm soil depth, whereas the DT was assigned to sub-soiling up to 60 cm soil depth alongside the traditional ploughing with a moldboard plow up to 30 cm soil depth. Both ZT and RT considered a conservation tillage in this study. Soil amendments (i.e. vermicompost and gypsum) were added with tillage process and directly before sowing of wheat grains, and sulfuric acid was added with irrigation water applied through the growing season. The amendments were applied to the soil at the rate of 10.0, 4.3 and 17.0 t ha− 1 for vermicompost, sulfuric acid (H2SO4) and gypsum (CaSO4.2H2O), respectively. The doses of gypsum and sulfuric acid were estimated according to the gypsum requirements (GR) for the investigated soil. The GR was calculated as follows:
(ESP1 − ESP2) ( 100 )
GR= 100 ×CEC ×1.72 × Gpurity (1)
where ESP1 is the initial value (23.0%), ESP2 is the required value (10.0%), CEC is the cation exchange capacity, and purity is 85.0%.
The gypsum was characterized as follows: pH, 7.0; electrical con- ductivity (EC), 2.2 dS m− 1; purity, 85.0%; particle size diameter, 50 × 10− 3 m; solubility, 2.9 g L− 1). Gypsum was calculated as the total of GR needed to reduce soil ESP from 22.0% to 10.0%, while the liquid reagent-grade of commercial sulfuric acid was calculated to be 25% of GR (Sadiq et al., 2007). Vermicompost was prepared in a vermi- composting bin with dimensions of 100 × 120 × 50 cm. Crop residues (rice, cotton and maize straw) were used as materials of vermicompost. Cow dung and green waste were used as worm feed, and the earthworm species called (Eisenia fetida and Dendrobaena veneta). The moisture content remained at 80% through the vermicomposting process. The chemical analysis of the prepared vermicompost included organic matter (42%), EC (3.2 dSm− 1), total N (2.1%), total P (10.8%), total K (0.5%) and pH (7.4).
The grains of wheat (i.e. cv. Shandweel1) were sown at the rate of 142.8 kg ha− 1 on November 20, 2016 and on November 19, 2017. The preceding crop was rice (Oryza sativa L.) in both seasons. The recom- mended dose of synthetic fertilizers of NPK were applied. Phosphorus fertilizer (40 kg P2O5 ha− 1) in the form of super phosphate (15.5% P2O5) was applied during the soil preparation stage. Nitrogen fertilizer (180 kg N ha− 1) in the form of urea (46.5% N) was divided into two equal doses and applied directly before the first and the second irrigations. However, the total dose of potassium fertilizer (60 kg K2O ha− 1) in the form of potassium sulphate (48% K2O) was added directly before the first irrigation. Irrigation of wheat plants during the two growing