EFFECT OF COTTONSEED MEAL WITH OR WITHOUT SOAPSTOCK,CANOLA MEAL,OR UREA ON SOIL FERTILITY AND GROWTH OF MARIGOLD AND REDBUD

The effects of incorporating or topdressing with cottonseed (Gossypium hirsutum L.) meal with or without soapstock, canola (Brassica rapa L.) meal, urea, or no amendment (control) were investigated using plants of marigold (Tagetes erecta L. ‘Inca II Gold’ or ‘Inca II Yellow’) and redbud (Cercis canadensis L.) in a Norge loam (fine-silty, mixed, thermic Udic Paleustolls) at Stillwater, OK in 2008 and 2009. Fertilizers were applied in May at 4.9 g?m^?2 N based on soil test results prior to the study and nitrogen (N) recommendations for turfgrass. Soil nitrate-nitrogen (NO₃-N) and phosphorus (P) increased from 2008 to 2009 in marigold plots into which cottonseed meal with soapstock was incorporated, and boron (B) increased in all marigold plots regardless of treatment. In 2009, marigolds grown in plots into which cottonseed meal was incorporated were taller than plants in other treatments except the untreated control. Marigolds in plots in which cottonseed meal was topdressed, cottonseed meal with soapstock was incorporated, or urea was topdressed grew less in height than plants in plots with cottonseed meal incorporated or control plots. Shoot dry weights of marigold plants in plots topdressed with cottonseed meal with or without soapstock, urea, or control plots were lower than those of plants in other treatments. Visual ratings of marigold plants receiving a topdress of urea or no treatment were lower than visual ratings of plants in any other treatment in July, but similar in August to those of marigold plants in plots in which cottonseed meal was topdressed. Some differences within fertilizer treatments occurred between 2008 and 2009 in redbud soil concentration of NO₃-N, calcium (Ca), magnesium (Mg), sulfate-sulfur (SO₄-S), iron (Fe), B, and copper (Cu). Leaf P concentration differed among fertilizer treatments in 2009. Leaf and total dry weight of redbuds grown in soil incorporated with urea was greater than that of plants in any other treatment. Results indicate that cottonseed and canola meals provide N and other nutrients for growth of landscape plants. Soil incorporated cottonseed meal encouraged more growth of marigold than soil incorporated urea but less growth of redbud.