Fruit Yield and Ascorbic Acid Content of Pepper Plants Grown in Soils Amended with Organic Fertilizers Under Field Conditions in Southwest Texas

Hot chili pepper (Capsicum annuum) production is a vital economic endeavor in the southwest of Texas. Organic fertilizers have been proposed as environmentally friendly alternative amendments to infertile soils that resulted from the intensified agricultural practices in chili pepper production. Manure (60 or 80 Ton/Ha) and three commercial products (Soil Secrets® Terra Pro, Protein Crumblies, and TTP Supreme compost) were tested in two fields to grow ‘Cayenne Mesilla’ and ‘Chichen-Itza Habanero’ chili pepper plants from May to September, 2015. In each field, a total of 180 chili pepper plants were planted in nine raised beds with 20 plants in two rows of each bed. Treatments were applied randomly to either half of the bed. Plants were watered daily through drip irrigation system, twice (8 am and 12 pm) during spring and three times (8 am, 12 pm and 3 pm) during summer with an average of 506 ± 110.8 mL per plant. Beds were covered with black weed barrier fabric. Plant height and two perpendicular widths were recorded weekly whereas chlorophyll fluorescence and SPAD readings were measured bi-weekly. Mature fruit were harvested weekly, and number of fruit and fresh weight (FW) were recorded. Aboveground shoots were harvested at the end of the growing season, and shoot fresh weight (FW) and dry weight (DW) were recorded. Ascorbic acid concentration was determined in mature fruit only. Data were analyzed with a factorial ANOVA at an α= 0.05 using SPSS statistics software. Results showed that plant height was different among treatments. At harvest, the manure treatment at 60 ton/Ha had the highest average fruit FW of 523.74 g per plant, shoot FW of 447.09 g per plant and shoot DW of 104.34 g per plant, while the Supreme compost treatment had the lowest average values of 371.3, 338.2, and 80.9 g per plant for fruit FW, shoot FW, and shoot DW, respectively. Chili pepper treated with manure at 60 ton/Ha had the lowest concentration of ascorbic acid (6.03 mg/g DW), while that in the control treatment had the highest ascorbic acid content (7.54 mg/g DW).