Abstract:
Sweet sorghum, an underutilized cereal crop, but a raw material for renewable bioethanol production by utilizing its juice, has been global interested as an important alternative energy crop for fossil resources, and has such a great potential for phytoremediation of arid saline lands, due to its high biomass and adaptation to harsh environments. With the objectives of increasing sugar, lowering input and improvement soil, a two-year field experiment was conducted in the saline- alkaline areas in Yellow River Delta (YRD), where the soil rich in potassium (K) but deficient of phosphorus (P). To evaluate the response of sweet sorghum to fertilization of P, K and manure (M) based on the parameters of juicy brix and nutrient content in each internode (IN) of the whole stalk, biomass and soil properties. The results showed that the peak of sugar content of sweet sorghum located in the middle IN but decreased at both lower and upper INs along with the normal distribution, so the middle INs hold higher brix that should be given priority utilizing. Application of K as topdressing promoted Brix values , together with N, P content of INs. Application of P as either base or dressing had no significant effect on Brix values and nutrient content despite the soil deficient in phosphorus. In contrast, applying of P combined with M stimulated sugar accumulation rapidly during sweet sorghum approaching maturity, improved Na content in INs and inhibited Na transferring to grains, shortened internode length, increased both the content of SOM and Ca in 0−60 cm , whereas decreased pH of 0−30 cm soil layer. The fertilization rates per hectare were recommended as: 80−120 kg P
2O
5 combined 213 kg organic matter, together with 90 kg N as basal, and 52 kg K
2O as topdressing during jointing stage, and stalk harvest on 138 d after seedling to obtain higher sugar, nutrient content, and improve soil fertility but reduce salinity as well. The above results provided a basis for subsequent planting sweet sorghum in saline soil, an important bioenergy crop, which will greatly facilitate the development of phytoremediation for both phosphorus-deficient and potassium-rich saline soils soil.