312 Composition of Leafy Greens as Affected by Season and Conventional or Organic Fertilization

Abstract

Nutrient availability may depend on method of fertilization particularly when the root medium is cool. The salad greens, arugula, lettuce, and spinach, were grown in spring, fall, and winter using organic or conventional fertilization to test this hypothesis. Field plots were mineral soil fertilized with 10N-10P-10K, or soil was amended with leaf compost and cotton-seed meal. Unheated high-tunnel plantings plots contained either perlite fertilized with a complete soluble fertilizer or a 1 leaf compost: 1 perlite mixture fertilized with cotton-seed meal. There was no consistent difference in growth due to the method of fertilization, either in the field or in high tunnels. Over all plantings in field and high-tunnel plots, concentrations of nitrogen and phosphorus were higher in leaves of plants grown with leaf compost. The time of year did not affect the difference in composition between plants grown in compost and perlite in a manner that could be related to the environment or rate of growth. Although relative growth rates were only 5% per day in high tunnels in winter compared to 10% to 18% per day in other seasons, the difference in reduced nitrogen among plants grown in compost and perlite was similar in winter and summer. The changes in composition due to method of fertilization were similar in all three plant species under study.