Organic Versus Conventional Fertilization of Pac Choi and Tomato Produced In the Field Versus High Tunnels Influences Crop Yield, Plant and Soil Nitrogen, and Phytochemical Content

High tunnel production provides a protected environment and extended season relative to open field production. An experiment was initiated to study crop yield, soil and plant nitrogen (N), and phytochemical content when using organic versus conventional fertility amendments. Spring and fall plantings of pac choi (Brassica rapa L. ‘Mei Qing’) and a summer planting of tomato (Solanum lycopersicum L. ‘Bush Celebrity’) were used to examine the effect of fertility rate (control, low, and high) and source [conventional (Conv) and organic (Org)] in different production systems [high tunnel (HT) and field (F)].  The experiment was conducted in 2008 at the KSU Research Center in Olathe in replicated HT and F plots.  Control plots received no supplemental fertilizer, low plots received pre-plant fertilizer of 20 N: 4.4 P: 16.6 K (Conv) or mixed source compost (0.6 N: 0.4 P: 0.4 K; Org), and high plots received the same pre-plant amendments plus soluble fertilizers of KNO₃+ Ca(NO₃)₂ (Conv) or fish hydrolyzate (Org).  All plots had cover crops of rye (Secale cereal L.) during the winter and buckwheat (Fagopyrum sagittatum Gilib.) in the summer between pac choi crops.  Soil NO₃-N and NH₄-N were measured, as well as NO₃-N in leaf petiole sap, based on the crop stage.  Phytochemical content of pac choi leaves and tomato fruit were measured as total phenolics and antioxidant capacity.  Soil NH₄-N and NO₃-N levels were affected by production system, and fertility source and rate, but statistical significance varied by crop and stage.  Petiole sap NO₃-N reflected treatment regimes but not necessarily soil N status at each plant stage.  Phytochemical data showed treatment differences between F and HT, but no clear or consistent differences between Conv and Org.  Yield of pac choi was higher in HT than F in both spring and fall.  Yield of Org pac choi in both HT and F was higher than Conv in the fall but not the spring. Pac choi yield in general reflected fertility rates. Tomato yield was also higher in HT  compared to F. Org HT tomato had higher yield than Conv, but no significant differences were observed in F. Tomato yield differences for fertility rate were significant in F but not in HT. The 2008 season is the first year of this multi-year, multi-disciplinary study.