SUSTAINABLE AND ORGANIC MANAGEMENT OF SELECTED FRUITS AND VEGETABLES
Title: EFFECT OF LIGHT INTENSITY, SOIL TYPE, AND LITHIUM ADDITION ON SPINACH AND MUSTARD GREENS LEAF CONSTITUENTS
Submitted to: Subtropical Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 31, 2006
Publication Date: December 12, 2006
Citation: Makus, D., Zibilske, L., Lester, G. 2006. Effect of light intensity, soil type, and lithium addition on spinach and mustard greens leaf constituents. Subtropical Plant Science. 58:36-43.
Interpretive Summary: Greens are an excellent source of minerals, vitamins, and other dietary constituents. Lithium salts have potential for pest control in organic agriculture. In this greenhouse study, we observed that when lithium sulfate is added to the soil at low levels (10 lbs /Ac), leaves of the spinach cultivar ‘Samish’ increased in vitamin C content by 17% and leaf total sulfur (inorganic and organic) concentrations in a mustard greens cultivar, Florida Broadleaf, increased by 60%. Plant fresh weights and leaf dry weights grown in one of the two soils used, were also increased by lithium applications to the soil. Soil type and light intensity were both found to influence mineral nutrient, plant pigment, and oxalate concentrations in spinach and mustard greens. Lithium, though not required by plants, is known to enhance general wellness in people.
A greenhouse experiment was conducted near Weslaco, Texas (Lat. 26o 8' N, Long. 97o 57' W) between 14 Dec. 2005 and 17 Feb 2006 to evaluate the effect of soil type, light environment, and lithium addition on the leaf nutrients of spinach and mustard greens. Cultivars Samish (Spinacia oleracea) and Florida Broadleaf (Brassica juncea) were sown in two soils, Hebbronville and Hidalgo (listed in order of increasing clay content), and grown in two light environments: ambient and ca. 50% of ambient. Greens grown under reduced light had greater leaf area, more chlorophyll and carotenoid pigments (dry wt. basis), total titratable acidity, total N, K, Mg, Na, Fe, and Li than leaves from plants grown in ambient light. The Hidalgo soil generally improved greens agronomic attributes, leaf pigments and total titratable acidity, total leaf N, and the mineral nutrients, Mg, S, and Na, compared to leaves from plants grown in Hebbronville soil. Greens type exhibited differences in most attributes tested. Li additions, at a field equivalent rate of 10 lbs Li / Ac, improved greens fresh wt., leaf dry wt., and S and Li leaf concentrations. Leaf ascorbate was 17% higher in ‘Samish’ given supplemental Li (P=0.07).