SUSTAINABLE AND ORGANIC MANAGEMENT OF SELECTED FRUITS AND VEGETABLES
Title: Spinach and mustard greens response to soil type, sulfur addition and lithium level
Submitted to: Subtropical Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 5, 2009
Publication Date: April 24, 2009
Citation: Makus, D.J., Zibilske, L.M. 2008. Spinach and mustard greens response to soil type, sulfur addition and lithium level. Subtropical Plant Science. 60:69-77
Interpretive Summary: Greens are an excellent source for minerals, vitamins and other dietary constituents. Modern fertilizer formulations are generally devoid of trace elements commonly found in animal fertilizers used in the past. One such trace element, lithium, also has the potential for pest control in organic agriculture. In this greenhouse study, we observed that when lithium chloride was added to the soil at levels between 0 to 40 lbs / Ac equivalent, several mineral nutrients and leaf protein were observed to increase in mustard greens. More importantly, we were able to increase lithium leaf content from about 1 ug/g dry leaf weight to 266 (in the case of spinach) and 414 ug/g for mustard greens. In mustard greens, total leaf sulfur (inorganic and organic) increased 39% at the highest lithium rate. A dramatic decrease in the leaf pathogen, downy mildew, was observed when lithium was applied at the higher rates. 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 Dec. 2006 and Feb 2007 to evaluate the effect of soil type, added sulfur and lithium level on the growth and leaf nutrients, particularly biofortified levels of Li and S, in spinach and mustard greens. Cultivars Samish (Spinacia oleracea) and Florida Broadleaf (Brassica juncea) were sown in two soils, Hebbronville and Hidalgo. Greens type exhibited differences in most attributes tested. Mustard greens (MG) grown in the lighter-textured Hebbronville soil produced plants with lower leaf and root dry wt., higher leaf transpiration and blade P, Mg, S, Li:K ratio, Zn, B and shoot and root Li. Spinach grown in the Hebbronville soil had a higher shoot:root dry wt. ratio and blade K, Ca, Mg and Li:K ratio. Sulfur addition (1 Mt / ha equivalent) had no affect on agronomic responses measured, but reduced leaf blade K (spinach, only), Ca (spinach, only) and increased P (MG, only) and S. The micronutrients Mn, Zn, Cu and B were reduced in spinach and Na, Zn and Cu increased in MG by sulfur addition. In MG (only), adding Li from 0 to 44 kg / ha reduced plant wt., leaf number, area, fresh wt., root dry wt., and the incidence of powdery mildew and increased leaf transpiration. In MG, increasing soil applied Li increased leaf blade N, K, P, Mg, S, Fe and Zn. In spinach, Li addition decreased leaf blade K, P, S, and B. Added soil Li increased shoot and root Li in both greens. All reported increases or decreases due to Li addition over the 0 to 40 kg Li / ha range were linear. The Li shoot to root ratio and shoot concn was higher in MG. Leaf blade S was reduced (r = -0.441**) by the presence of blade Li in spinach, but increased in MG (r = 0.496**). The ratio of leaf blade Li:K was approx. 4 X higher in MG, which may have interfered with somatal regulation (higher leaf transpiration in MG with increasing Li applied).