The effect of nitrogen and late blight on crop growth, solar radiation interception and yield of two potato cultivars

Two field experiments were conducted in 2006 and 2007 at Braunschweig, Germany, to assess the effects of N supply and late blight infestation on crop growth dynamics of potato in terms of RI, RUE, and dry matter (DM) accumulation. Four nitrogen supply levels (unfertilised up to 160 kg N ha−1 N supply (soil mineral + fertilisation) in 2006, unfertilised - 240 kg N ha−1 in 2007) were tested in combination with two fungicide regimes (sprayed, unsprayed) in two cultivars differing in maturity. N fertilisation increased leaf area index (LAI), leaf area duration (LAD), and RI, and in consequence, tuber yield, but had no significant effect on RUE within a single cultivar. Late blight infection caused premature senescence and defoliation resulting in smaller LAI, shorter LAD, less RI and lower tuber yields. Late blight had no effect on RUE if leaf area was corrected for disease severity. Significant interactions between N level, fungicide treatment and cultivar on late blight disease spread were found affecting LAI and RI. This study shows that total DM accumulation of potatoes can be predicted by RI and RUE, even if N supply is limited and late blight control incomplete as long as the late blight effect on RI can be properly estimated.