Long term effect of fertilization and manuring on productivity of some potato based cropping systems in Punjab

A long term field experiment was conducted at Central Potato Research Station, Jalandhar on alluvial soil to study the effect of continuous cropping and manurial treatments between 1970 to 1987 on productivity of 4 potato based cropping systems and the component crops. The mean annual productivity in terms of potato equivalent yield was 262, 272, 388 and 262 q/ha for potato-wheat-rice (P-W-R), potato-wheat-maize (P-W-M), potato-potato-maize (P-P-M) and potato-potato-maize-wheat-green manure (P-P-M-W-GM) system respectively. The P-P-M-W-GM system could not trade off the loss of one crop in the annual crop production potential as compared to P-W-M and P-P-M system but could compensate the loss of one crop as compared to P-W-R system. A decline in productivity from the initial level ranging from 2.2 to 3.1% per year was recorded in all the cropping systems. The decline in productivity of a crop was maximum in control, where only N had been applied. But the application of P and K through inorganic fertilizers or farmyard manure to only potato or to alternate crops in a system tended to arrest the rate of decline. The results emphasised the need for increased frequency of manuring the crops with PK or FYM.