Effects of Nitrogen, Phosphorus and Potassium Combined Fertilisation on the Dry Matter Accumulation, Distribution and Yield of Potato Under Ridge and Furrow Film Mulch Cropping

The promotion of ridge-furrow and film mulching technology has led to a drastic increase in potato cultivation in the semi-arid northwest China. However, the optimal nitrogen (N), phosphorus (P) and potassium (K) combined fertilisation regime is still unclear under the planting pattern. The aim of this study was to assess the effects of N, P and K upon the dry matter accumulation and yield formation of potato under ridge and furrow film mulching cropping in a two consecutive year field experiment in a semiarid region. Nitrogen (four N rates), phosphorus (four P rates) and potassium (four K rates) were applied at planting: at combined rates of 0, 75, 150 and 225 kg N ha(-1), and at rates of 0, 37.5, 75 and 112.5 kg P ha(-1) and 0, 60, 120 and 180 kg K ha(-1). The results suggested that fertilisation with N, P and K at various levels exerted differential effects on dry matter accumulation of the whole plant and tubers, as well as tuber yield per plant. The highest N rate slowed dry matter accumulation, altered source-sink relations and reduced tuber yield per plant. However, higher P and K rates had a positive effect on those parameters, promoting the timely transfer of assimilates to tubers and facilitating dry matter accumulation in the tubers, so that tuber yield per plant increased. A medium N and higher P rates augmented the tuber dry matter content at the rapid accumulation stage, while adding more P had marginal effects on dry matter accumulated. An optimal N, P and K combined fertilisation strengthened dry matter accumulation of tubers. Under treatment 7 (i.e. N2 +P3 +K2), dry matter accumulation occurred sooner, its duration was shorter and both maximum dry matter growth rate and mean dry matter accumulating rate were greatest; large tuber mass, yield per plant and yield per plot were all maximised vis-a-vis the other treatments. Therefore, medium N and K applications and the highest P fertilisation level are optimal to promote tuber expansion and yield of potato.