Effect of early blight (Alternaria solani) and different nitrogen inputs on radiation interception, radiation use efficiency, and total dry matter production in potatoes (Solanum tuberosum) grown in Canterbury, New Zealand

Abstract

Field experiments were conducted in 1995/96 and 1996/97 to investigate the effect of early blight epidemics on photosynthetically active radiation (PAR) interception (RI), radiation use efficiency (RUE), and total dry matter (TDM) production of potatoes (Solanum tuberosum) grown in Canterbury, New Zealand. RI was calculated from green leaf area index (GLAI) corrected for disease. RUE was calculated as the ratio between accumulated TDM and accumulated RI. Early blight reduced RI by 9% in both seasons and RUE by 17% and 28% in 1995/96 and 1996/97 respectively. There was a total loss of 26% and 36% in TDM in 1995/96 and 1996/97 respectively. Nitrogen inputs increased RUE by 3% and 16% as compared to low nitrogen status in 1995/ 96 and 1996/97 respectively. Results showed that RI and RUE, calculated from leaf area index (LAI), not corrected for disease, underestimated the loss in RI and RUE.