EFFECT OF BIOFERTILIZER AND COMPOST ON NITRATE STATUS, YIELD AND QUALITY OF POTATO TUBER UNDER NEWLY RECLAIMED SANDY SOIL

This investigation was carried out during the two summer seasons of 2015 and2016 in sandy soil on potato culitvar "Sante" to study the effect of using 100%compost (15 t/fed.) and 50% compost + nitrogen fixing bacteria (Azotobacter, andPseudomonas alone or together) on potato yield and quality as compared to theconventional mineral fertilization (120-75-150 kg/fed. NPK + 5 toncompost/fed.(control)). No significant differences in tubers yield/fed. were detectedbetween mineral fertilization (control) and using 100% compost (15t/fed).However, control treatment significantly produced a high yield per feddan,more than using 50% compost + any biofertilizer treatment.Using composttreatment at 15 t/fed.execeed all biofertilizer treatments in marketable yield in bothseasons, but without significant differences as compared with mineral fertilization(control).No significant differences in tuber dray matter and content of starch intuber were found between using compost treatment at 15 ton/fed. and mineralfertilization treatment (control)in both seasons. Nevertheless, application of 50%compost+ 4 applications of Azotobacter and Pseudomonas had the highest tuberconcentrations of starch and nitrogen with significant differences as compared withthe mineral fertilization.Using50% compost + 4 applications of Azotobacter orPseudomonas or both (Azotobacter + Pseudomonas )and application of 100%compost caused producing potato tubers with the lowest concentration of nitratewith significant differences as compared with the mineral fertilization. Nosignificant differences were detected between mineral and organic fertilizersconcerning P and K concentrations in tubers