Optimizing the potassium (K) dose of fertigation for the Nagpur mandarin (Citrus reticulate Blanco)

To standardize the potassium sulphate fertilizer dosethrough fertigation system during three Ambia flowering (October flush) onyield and quality of 14-16 years Nagpur mandarin a field experiment wasconducted at National Research Centre for Citrus, Nagpur during 2009-2012. TheNagpur mandarin plants requires potassium besides N and P which, when appliedin during the flower bud initiation to before fruit maturity can affect theyield and fruit quality. The treatments in experiment consisted of; F1-Fertigation with 20 g K2O/plant/month, F2- Fertigation with 30 g K2O/plant/month,F3- Fertigation with 40 g K2O/plant/month and F4- Fertigation with 50 gK2O/plant/month. The recommended fertigation dose was 500:150:150 (N:P:K) andgiven through these treatments along with various fertilizers combination ofurea of phosphate, urea and potassium sulphate. Nitrogen and phosphorus wasgiven from October to January month and N, P and K all were given from Februaryto June month. Each fertigation treatment was given at 30 days interval andfruit yield and quality were measured at harvest. Results showed the highestresponse of the fruit yield (26.67 tonnes/ha) with 50 g K2O/plantpotassium sulphate followed by in K-fertigation with 40 g K2O/plantdose (25.52 tonnes/ha). The total soluble solids was highest (9.74 0Brix) in Kfertigation with 50 g K2O/plant dose followed by fertigation withpotassium sulphate 40 g K2O/plant dose (9.61 0Brix). Highest juicecontent (39.72 %) and low acidity (0.86 %) was found in K fertigation withpotassium sulphate 50 g K2O/plant dose. The highest TSS to acidityratio (sweetness indicator) was observed in 50 g K2O/plant dose(11.32) followed by 40 g K2O/plant dose Potassium sulphate (10).