Effects of Biogas Slurry Combinated with Urea on Photosynthetic Characteristics and Grain Yield of Winter Wheat

Abstract

A two-year field experiment was carried out to study the physiological basis of photosynthesis when biogas slurry was jointly applied with urea in wheat(Triticum aestivum L.) and to suggest the proper method for applying biogas slurry.Under the control of total input of nitrogen,the treatments with basal biogas slurry and topdressed urea showed relative high values of PSII potential activity(Fv/Fo),the maximal quantum efficiency of PSII photochemistry(Fv/Fm),photochemical quenching coefficient(qP),electron transport rate(ETR),overall photochemical quantum yield of PSII(ΦPSII),and Pn and low values of non-photochemical quenching coefficient(qN) of flag leaf from heading to maturity of wheat.The best performance of Pn and chlorophyll fluorescence parameters was observed in the treatment of basal biogas slurry(25%) + topdressed urea(75%),which also showed the highest yield of 8 277.90 kg ha-1 and 7 318.07 kg ha-1 in 2007–2008 and 2008–2009.The only application of biogas slurry resulted in poor chlorophyll fluorescence parameters and low Pn because of plant malnutrition,and ultimately a significant lower yield than other treatments.Although the highest Fv/Fo and Fv/Fm were observed in the treatment with urea applied only at heading stage,there were obvious unbalanced chlorophyll fluorescence parameters,such as a continuously low level of qP,a continuously high level of qN,and the unstable ETR and ΦPSII across years.The results suggest that the proper application of biogas slurry in combination with chemical fertilizers may promote grain yield of wheat through optimizing photosynthetic functions,and biogas slurry applied before sowing is better than topdressed at jointing stage.