Release Mechanisms and Kinetic Models of Gypsum-Sulfur-Zeolite-Coated Urea Sealed with Microcrystalline Wax for Regulated Dissolution

Supporting Information: The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.0c04353. Release of nitrogen content from uncoated urea and commercial sulfur-coated urea (SCU) determined by the HPLC method and the Kjedhal method (PDF).Copyright © 2021 The Authors. In this study, a mineral-based coated urea was fabricated in a rotary pan coater using a mixture of gypsum/sulfur/zeolite (G25S25Z50) as an effective and low-cost coating material. The effects of different coating compositions on the dissolution rate of urea and the crushing strength and morphology of the coated urea were investigated. A 25:25:50 (wt %) mixture of gypsum/sulfur/zeolite (G25S25Z50) increased the coating effectiveness to 34.1% with the highest crushing strength (31.06 N). The effectiveness of coated urea was further improved to 46.6% with the addition of a microcrystalline wax (3%) as a sealant. Furthermore, the release mechanisms of various urea fertilizers were determined by fitting the release profiles with six mathematical models, namely, the zeroth-order, first-order, second-order, Higuchi, Ritger & Peppas, and Kopcha models. The results showed that the release mechanism of the uncoated urea and all other coated urea followed the Ritger & Peppas model, suggesting the diffusional release from nonswellable delivery systems. In addition, due to the increased mass-transfer resistance, the kinetic constant was decreased from 0.2233 for uncoated urea to 0.1338 for G25S25Z50-coated urea and was further decreased to 0.0985 when 3% Witcovar 146 sealant was applied.Rachadapisaek Sompot Fund, Chulalongkorn University, for the postdoctoral fellowship; Petronas Company; Universiti Putra Malaysia

Biplot Analysis of Three Carthamus Species and their F2 Hybrids Evaluated under Drought Stress in Seedling Stage

Drought stress is one of the most important environmental factors affecting growth, development and production of crop plants. Drought tolerance in germination and seedling growth stage is very important especially for crop production in dry regions. Sufficient genetic diversity in cultivated species of safflower is limited and seems to be of potential benefit in search of wild species. In this study drought tolerance of three Crathamus species and their respective F2 hybrids (direct and reciprocal from paired crosses) was evaluated under four levels of osmotic potential of polyethylene glycol (0, -5, -10 and -15 bars) using a factorial experiment based on the completely randomized design with three replications. Increasing water stress levels caused significantly more reductions in the germination, root length, shoot length, root dry weight, shoot dry weight and seedling dry weight of cultivated genotypes as compared with wild species C. palaestinus (Cp), C. oxyacanthus (Co) and their F2 progenies indicating that wild species sustained more moisture stress tolerance than cultivated species. Results of drought tolerance indices (such as TOL and STI) also confirmed that wild species and F2 progenies had more drought tolerance in germination stage. Biplot analysis, according to principle component analysis (PCA), indicated that C. tinctorius was the most sensitive and the hybrids of C. oxyacanthus × C. palestinus were the most drought tolerant genotypes which can be due to heterosis. Results also showed that the F2 hybrids from crosses between cultivated species (C. tinctorius) and wild species (C. oxyacanthus and C. palestinus) had high tolerance to drought stress and can be used for developing drought tolerant genotypes in inter-specific hybridization breeding programs