Study On Fertigation Technology And Spatial-temporal Distribution Of Water-fertilizer In Yam Production

Excessive water and fertilizer were blindly applied in yam(Dioscorea oppositifolia L.)production when farmers pursue the single goal of high yield.The results not only induce to underground ecosphere imbalance,low yield as well as inefficient water and fertilizer utilization,but also strengthen the risk of environmental pollution and restrict the sustainable development of yam industry.In this study,status of fertilization and soil fertility for 4 main cultivars were investigated in the main producing area of Hebei.Topdressing management were conducted with fertigation,and then spatial-temporal distribution of water and fertilizers were measured.The research aims to provide the theoretical basis and technical support to optimize water and fertilizer management in yam production,promoting a high yield and high-efficiency production.The main results were summarized as follows:(1)Soil fertility of yam fields:Organic matter and total nitrogen(N)in the topsoil were at a deficient level.Slowly available potassium(K)and secondary nutrients were at a very high level.Nitrate and available cuprum(Cu)were at a medium level.Available phosphorus(P),K,iron(Fe)and manganese(Mn)were high,and available zinc(Zn)content was low.The results showed that soil fertility of yam field was low.Thus,introducing organic fertilizer in yam fertilizer may be a solution to improve soil fertility in practice.(2)Nutrient input of yam:The total input amount of N,P2O5,K2O in yam production was high and averagely reached(746±119)kg/hm2,(641±187)kg/hm2 and(941±149)kg/hm2,respectively,with a ratio of 1:0.86:1.26.And these fertilizers had rather large variation in application rates.Three fertilizers accounted for 83.0%,88.6%and 91.3%of the corresponding total nutrient,respectively.This result indicated the application rate of organic fertilizer was low,and farmers are lack of scientific guidance for chemical fertilizers in yam production.(3)Content and accumulation of soil nitrate and available K increased with the yam growth.And nitrate and available K also migrated to the lower soil with the development of yam.Soil available P content slowly decreased with the growth process,but the total cumulative amount did not significantly change.N,P and K nutrients in yam field were all in surplus state,and higher than 39.3%,251.2%and 314.4%respectively compared to the growth demand.The larger nutrient surplus increased the risk of nutrient loss and environmental pollution.(4)Under the effect of a large basic fertilizer application,the higher N topdressing rate was not conducive to the yield and commodity rate of yam,but topdressing P an K showed a significant incremental effect,topdressing Mg fertilizer was not significant.Urea and ammonium sulfate(AS)had no obvious positive effect on yield and accumulation of N and P.the AS was beneficial to the increase of commodity rate of yam,while urea increased the nitrate content in surface soil layer.The application of monoammonium phosphate(MAP)reduced the pH in 0-20 cm soil layer during the yam growth period.Ammonium polyphosphate(APP)had strong mobility in the soil,which was beneficial to promote the availability of P content and accumulation in the 0-20 cm and 20??40 cm soil layers,and significantly increased the yield and rhizome P accumulation of yam.(5)Soil moisture and nutrient distribution under fertigation technology:During the growth process,nitrate accumulation peak in soil showed a slowly decline trend,available P content in the surface soil layer gradually decreased,but available K content of 0?100 cm soil layer gradually increased.The content of available P and K decreased with soil layer deepening at each growth period of yam.The nitrate transport distribution in soil was mainly affected by soil moisture during the two topdressing period.After 1 day of topdressing,the water content in upper 40 cm soil layer reached the peak,while the content of nitrate in upper 40 cm soil layer and available P in 0-20 cm soil layer decreased significantly,and then gradually increased.After 3 day of topdressing,the soil available K content reached the greatest,but the overall spatial and temporal changes were stable during the two topdressing irrigation periods.It can be seen that the amount of N,P and K in the production of yam is surplus and varies greatly,resulting a severely leaching of nitrate and available K.With fertigation technology,a proper amount of topdressing P and K fertilizer has a remarkable effect,and the APP is optimal.The application of Mg fertilizer and different N sources has little effect on the yam yield.And the distribution characteristics of soil moisture and available nutrients are defined.