Effects Of Nitrogen And Phosphorus Coapplication On Growth,Physiology,and Yield Of Sorghum Grown In Saline Soils

Sorghum is one of the world’s five major cereal crops and an important source of food,feed and raw materials for brewing.Sorghum not only has wide adaptability but also has strong stress resistance,and salinity tolerance is one of its main characteristics.Planting sorghum in saline-alkali land can increase sorghum yield and make reasonable use and allocation of marginal soil,which can effectively alleviate the tension of arable land resources.This experiment takes Jitan No.3 sorghum variety as the experimental material to study the effects of nitrogen application rate(N0=0 kg N·ha-1,N1=180 kg N·ha-1,N2=360 kg N·ha-1)and phosphorus rate(P0=0 kg P·ha-1,P1=60 kg P·ha-1,P2=120 kg P·ha-1)were studied on the growth characteristics,morphology index,physiological properties,yield and nutrient utilization efficiency of sorghum in saline-alkali land,in order to lay the foundation for building technology for high yield sorghum cultivation in saline-alkali land.The main experimental results are as follows:1.Effects of nitrogen and phosphorus coapplication rates on growth and morphological indices of sorghum.The plant height,stem diameter and biomass of sorghum were significantly increased with appropriate nitrogen fertilizer or phosphorus fertilizer,but the morphological indexes were decreased with excessive nitrogen fertilizer or phosphorus fertilizer.The biomass and morphological indices of sorghum under N and P combined treatment were significantly higher than those under N or P alone.In general,the plant height and stem diameter of Jitan No.3 sorghum reached the maximum under N1P1 treatment,while the biomass reached the maximum under N2P2 treatment,which was 18,534.9 kg·ha-1.2.Effects of nitrogen and phosphorus coapplication rates on physiological indexes of sorghum.The application of N and P fertilizers has significant effects on physiological indexes of sorghum.The response trend of each physiological indexes to N and P treatments was the same.The current studies showed that a single application of N and P fertilizers promotes the accumulation of soluble sugar,protein and proline contents in sorghum leaves and stems.Moreover,the higher application of N2 and P2 reduce the accumulation of osmotic regulatory substances in sorghum.The combined application of N and P,such as N1P1 and N2P2,accumulates large quantities of osmotic regulatory substances in sorghum and improve the permeability of sorghum in saline-alkali land.N and P fertilizers improve antioxidant enzymes such as SOD,POD,CAT and APX in sorghum leaves.The antioxidant activities reduce the higher accumulation of reactive oxygen species(ROS)such as O2-and H2O2 in sorghum.As compared with the single application of N and P,the combined application of N and P significantly improved the effects of antioxidant activities of sorghum and reduced the adverse of ROS.In addition,the combined application of N and P can significantly reduce MDA content,reduce the relative conductivity of cell membrane,promote the accumulation of chlorophyll contents,improve the photosynthetic activities,promote the accumulation of carbon assimilates,and the performance of N and P in sorghum under saline-alkali soil.The current study indicated that combined application of N and P improved antioxidant activities as compared to the single application of N and P,but the combined ratio of N and P considerably performed best.3.Effects of nitrogen and phosphorus coapplication rates on physiological indexes of sorghum.Appropriate application of N and P fertilizers significantly improves sorghum yield.The combined application of N and P ratios was significantly increased yield as compared with the single application of N or P.The maximum yield 5967.8 kg·ha-1 was recorded under the combined application of N1P1(180 kg N·ha-1 60 kg P·ha-1).The performance of the harvest index of Jitian No.3,was different from that of the yield under different treatments.The harvest index of Jitian No.3 under different treatments was significantly higher than that under the combined application of N and P.The maximum value of the harvest index was recorded 0.252 under N1P0 and N0P2 treatments.In addition,the suitable amounts of N and P application significantly improve the N and P utilization efficiency of Jitian No.3,but have no significant effecton K utilization efficiency.The combined application of N and P reduced the N and P utilization efficiency of sorghum as compared with control.The highest N utilization efficiency was recorded in N0P1 and N0P2 application,both of which were 36.8kg·kg-1.The highest phosphorus utilization efficiency was recorded in N1P0(140.8 kg·kg-1)application.