Nitrogen-molybdenum-manganese co-fertilization reduces nitrate accumulation and enhances spinach (Spinacia oleracea L.) yield and its quality.

Spinach (Spinacia oleracea L.) is considered a nitrogen (N) intensive plant with high nitrate (NO3 -) accumulation in its leaves. The current study via a two-year field trial introduced an approach by combining N fertilization from different sources (e.g., ammonium nitrate; 33.5 % N, and urea; 48 % N) at different rates (180, and 360 kg N ha-1) with the foliar spraying of molybdenum (Mo) as sodium molybdate, and/or manganese (Mn) as manganese sulphate at rates of 50 and 100 mgL-1 of each or with a mixture of Mo and Mn at rates of 50 and 50 mg L-1, respectively on growth, chemical constituents, and NO3 - accumulation in spinach leaves. Our findings revealed that the highest rate of N fertilization (360 kg N ha-1) significantly increased most of the measured parameters e.g., plant length, fresh and dry weight plant-1, number of leaves plant-1, leaf area plant-1, leaf pigments (chlorophyll a, b and carotenoids), nutrients (N, P, K, Fe, Mn, Zn), total soluble carbohydrates, protein content, net assimilation rate, and NO3 - accumulation, but decreased leaf area ratio and relative growth rate. Moreover, plants received urea-N fertilizer gave the highest values of all previous attributes when compared with ammonium nitrate -N fertilizers, and the lowest values of NO3 - accumulation. The co-fertilization of N-Mo-Mn gave the highest values in all studied attributes and the lowest NO3 - accumulation. The best treatment was recorded under the treatment of 360 kg N-urea ha-1 in parallel with the combined foliar application of Mo and Mn (50 + 50 mg L-1). Our findings proposed that the co-fertilization of N-Mo-Mn could enhance spinach yield and its quality, while reducing NO3 - accumulation in leaves, resulting agronomical, environmental and economic benefits.

Onion (Allium cepa L.) peels: A review on bioactive compounds and biomedical activities.

Huge quantities of byproducts/wastes generated in onion processing are usually discarded, but they are excellent sources of bioactive compounds and phytochemicals. However, with growing interest in the sustainable use of resources and the circular economy to reduce adverse impacts on the environment, food processing wastes such as onion peel/skin can be extracted and employed as inputs in developing or reformulating nutrient supplements, and pharmacological drugs. This review highlights major bioactive components, especially total phenolics, total flavonoid, quercetin and its derivatives present in onion peel/skin and their therapeutic applications as cardioprotective, neuroprotective, antiobesity, antidiabetic, anticancer and antimicrobial agents. The present review emphasized that onion peel is one of the important agricultural by-products which is rich in bioactive compounds and can be utilized as health promoting ingredient especially in pharmacological and biomedical fields. Thus, with increasing burden of life style disorders/non-communicable diseases, finding suitable natural alternative for their treatment is one major concern of the researchers and onion peel and its extract can be exploited as a prime ingredient.