Short-term Effects of Composted Cattle Manure or Cotton Burr on Growth, Physiology, and Phytochemical of Spinach

Compost is increasingly used in horticultural crop production as soil conditioner and fertilizer because of its contribution to agriculture sustainability. The short-term (35 days after transplanting) effects of composted cattle manure or cotton burr on growth, physiology, and phytochemical of spinach (Spinacia oleracea L.) were evaluated in a greenhouse. Composted cattle manure at 5% or 10% mix rate (5Ca or 10Ca) greatly enhanced spinach growth as indicated by increased leaf number, area, fresh and dry weights (FW and DW), shoot FW and DW, and root DW. They also increased water use efficiency (WUE) and shoot: root ratio, and improved the photochemistry of mature leaves. Chlorophyll content also increased under 10Ca treatment. Composted cotton burr also improved spinach growth but only at 10% amendments (10Co), and was less efficient than composted cattle manure. Specific leaf area (SLA) decreased and succulence increased under all compost amendment indicating that compost could improve spinach quality. All soil amendments reduced the content of total phenolic and anthocyanin, while only 10Co and 5Ca treatments decreased flavonoid content and total antioxidant capacity. The content of carotenoid and protein increased in 10Ca treatment and amino acid content increased under both 5Ca and 10Ca treatments. The results indicated that compost, especially composted cattle manure mixed at 10%, improved spinach production and quality, and with proper application rate enhanced nutritional value by increasing carotenoid, protein, and amino acid contents while having little effect on total antioxidant capacity.