Manganese Toxicity in Watermelon as Affected by Lime and Compost Amended to a Hawaiian Acid Oxisol

Abstract

<jats:p>Manganese (Mn) toxicity in crops is a serious problem in Hawaii, especially Kauai and Oahu, where most soils are highly weathered. To devise a management strategy to control Mn toxicity, a greenhouse experiment was conducted on an acid (pH 4.4) Oxisol (Wahiawa series) having 15g·kg<jats:sup>-1</jats:sup> total Mn. Factorial combinations of lime (0, 2.0, and 4.0 g·kg<jats:sup>-1</jats:sup> CaCO<jats:sub>3</jats:sub>) and two composts (made from chicken manure and from sewage sludge at 0, 5, and 10 g·kg<jats:sup>-1</jats:sup>) were applied to the soil, which was subsequently planted to watermelon (<jats:italic>Citrullus lanatus</jats:italic> Thunb. `Crimson Sweet'). Our preliminary results showed that: 1) liming reduced Mn extractability and phytoavailability, but the reduction in Mn per unit increase in pH was much less than predicted by theory; 2) for good watermelon growth, soluble Mn, as extracted by the saturated paste method, should be &lt;2.0 mg·L<jats:sup>-1</jats:sup> corresponding to a soil pH &gt;5.7; 3) unlike the saturated-paste extractable Mn, the Mehlich3-extractable Mn varied less with pH in a given soil series than between soil series; 4) effects of composts on Mn toxicity varied with compost properties, especially their Ca content and pH altering capacity; and 5) the diagnostic criteria for Mn toxicity in watermelon are tentatively proposed as: leaf Mn &gt;1000 mg·kg<jats:sup>-1</jats:sup> and leaf Ca/Mn ratio (g·g<jats:sup>-1</jats:sup>) &lt;25.</jats:p>

Elaboration, characteristics and advantages of biochars for the management of contaminated soils with a specific overview on Miscanthus biochars

“…Indeed, these soils (which are referred to as Ultisol and Oxisol) are known to contain high concentrations of Al (Vityakon and Seripong, 1989) that can be reduced by biochar addition through: i) the increase of soil pH and ii) the input of organic material which decreases the part of exchangeable Al through adsorption processes and decreases the toxicity of Al through chelation with organic compounds from biochars (Haynes and Mokolobate, 2001;Hue et al, 1986). The decrease of the Mn content could be attributed to the increase in Ca availability, which reduced MneCa competition for plant uptake (Hue and Mai, 2002). Another proof of the beneficial aspects of biochar was given by Olmo et al (2014), who observed increases in fine root proliferation and crop development after soil amendment by olive tree pruning biochar.…”

Cultural Conditions Contributing to Vine Decline Syndrome in Watermelon

“…As soils in southwestern Indiana are often acidic, Mn 2+ toxicity could contribute to inhibition of watermelon root growth. Acid pH increases Mn 2+ solubility and phytoavailability which results in toxicity (Hue and Mai, 2002). Mn 2+ toxicity is characterized by competition with Mg 2+ uptake and utilization: Mn 2+ can compete with cation uptake, displace Mg 2+ enzyme co-factors, displace Ca 2+ in cell membranes and enhance axilliary shoot growth (Marschner, 1995).…”

Compost and Compost Tea Management of Mini Watermelon Cultivations Affects the Chemical, Physical and Sensory Assessment of the Fruits

“…The efficacy of AWC soil amendment and CTB foliar spray were particularly evident on the qualitative intrinsic parameters of the fruits rather than on agronomic traits while, MWC decreased overall parametric set. Few previous studies concerning the use of the compost to grow plants of this species highlighted a low sensitive yield response to compost amendment [33], as well as more different effects depending by soil type and compost property [34]. Likely, this particular behaviour is due to the continue struggle between compost, promoting growth factors, and the appearance of allelopathy to which watermelon is reported to be very sensible [35] [36].…”