Growth and composition of salad greens as affected by organic compared to nitrate fertilizer and by environment in high tunnels
2002
Gent, M.P.N.
Form of fertilizer affects composition of salad greens. This response may vary with growth rate or environment during growth. The interaction of environment and form of fertilizer was examined for salad greens grown as successive plantings in unheated high tunnels. Eight species, including eleven plantings of lettuce and spinach, were grown with either a nitrate-based complete soluble fertilizer in perlite or with an organic fertilizer, namely leaf compost: perlite 1:1 v/v amended with cottonseed meal. For each species, relative growth rate and specific leaf area varied with time of year. Fertilizer had little effect on growth rate, but specific leaf area was generally greater for plants with organic fertilizer. For many species, leaf concentrations of nitrogen (N), phosphorus (P), potassium (K), and calcium (Ca) were raised by 10 to 20% with organic, compared to nitrate-based, fertilizer. However, some species responded differently. For instance, organic fertilizer lowered Ca in spinach and nitrate and K in kale. The nutrient concentrations varied with time of year, but each nutrient had a different pattern. The seasonal variation was similar in magnitude to that due to fertilizer. Interaction of effects of season and fertilizer were significant only for N and P in lettuce. Salad greens grown in high tunnels had low concentrations of nitrate, and nitrate varied less with fertilizer or season than did total or reduced N.
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