Effects Of Combined Application Of Biogas Slurry And Chemical Fertilizer On Rhizosphere Biological Activities, Physiology Character, Yiel And Quality Of Winter Wheat

Biogas slurry from agricultural waste treatment contain considerable amounts of plant nutrients, and their use may offer a promising win-win opportunity to improve crop production and prevent adverse environmental impacts of waste disposal. To investigate the effects of combined application of biogas slurry and chemical fertilizer on soil biological activity, photosynthetic characteristics, C/N metabolism, yield and quality in winter wheat, six different treatments of total nitrogen amount 240 kg·hm-2 with mixed chemical and biogas slurry fertilizers, chemical N only with basal N 50% and topdressing N 50% (1/2U+1/2U, urea as N), 25% chemical N as basal fertilizer and 75% biogas slurry N as topdressing fertilizer (1/4B+3/4U), half chemical fertilizers with basal N and half biogas slurry with topdressing N (1/2B+1/2U), half biogas slurry N as basal fertilizer and half chemical N as topdressing fertilizer (1/2 U+1/2 B), 75% biogas slurry N as basal fertilizer and 25% chemical N as topdressing fertilizer (3/4 U+1/4 B), biogas slurry N only with basal N 50% and topdressing N 50% (1/2B+1/2B) were respectively arranged in a randomized block design with three replicates in 2007-2009. In each plot (3 m×7 m), base fertilizers was applied before sowing, and topdressing fertilizers was applied at jointing stage. Additional P2O5 (150 kg hm-2) and K2O (120 kg hm-2) were supplied as basal fertilizer. The results as follows:1. The Chl content, net photosynthetic rate(Pn) and six fluorescence dynamic parameters of the flag leaf, PSⅡpotential activity (Fv/Fo), the maximal quantum efficiency of PSⅡphotochemistry (Fv/Fm), photochemical quenching coefficient (qP), non-photochemical quenching coefficient (qN), the apparent photosythetic electron transport rate (ETR), and overall photochemical quantum yield of PSII (Yield) were measured at booting, heading, flowering, middle filling, late filling, and harvest stages, respectively. Grain yield and its structures at each treatment were calculated for comparison. The results indicated that Fv/Fo, Fv/Fm, qP, ETR,ФpsII, and Pn of flag leaf in the treatment of 25% chemical N as basal fertilizers and 75% biogas slurry N as topdressing fertilizers (1/4B+3/4U), especially the treatment of 50% biogas slurry N as basal fertilizers and 50% chemical N as topdressing fertilizers (1/2B+1/2U) were raised and qN was decreased, compared with the other treatments. The treatment of biogas slurry N only (1/2B+1/2B) led to poor chlorophyll fluorescence parameters and Pn because of plant malnutrition, with grain yield significantly decreasing. The treatment of chemical fertilizer N only (1/2U+1/2U) resulted in the highest Fv/Fo and Fv/Fm before anthesis and reduced these after anthesis, with reverse trend for ETR and Yield of PSⅡ, and like the lack of harmony between the photosynthetic functions of flag leaves decreased photosynthetic rat, with lower grain yield for the treatment of 1/2U+1/2U than the treatment of 1/4B+3/4U with significant difference, and significant higher than the treatment of biogas slurry N only. It is suggested that proper biogas slurry application combined with chemical fertilizers may promote grain yield by optimizing photosynthetic functions, and harmonizing photosynthetic parameters.2. The results indicated that the quantity of wheat root microorganism and enzyme activities of urease and catalase in soil first increased and then descended as growth progress, with change as S-type trend for protease. The optimum on combined application of biogas slurry and chemical fertilize as 1/4B+3/4U and 1/2B+1/2U can obviously increase the quantity of soil microoganisms and improve the activities of urease and protease, with worse effects of the treatments of chemical N only and biogas slurry N only on the quantity of soil microoganisms and the activities of urease and protease. The treatments of 1/4B+3/4U and biogas slurry N only resulted in the highest catalase activity during all measuring dates, with significant difference among measured dates for effects of other treatments on catalase activity. The results suggested that proper biogas slurry application combined with chemical fertilizers would lead to increase the quantity of microbes and enzymes activity in soil, to promote soil nutrient metabolism and micro-ecosystem quality with reverse trend for the treatments of chemical N only and biogas slurry N only.3. Winter wheat flag leaf nitrogen content descended gradually as growing progress, leaf nitrogen content of treatments of urea N as topdressing fertilizer (1/2U +1/2U, 1/2B +1/2U, and 1/4B +3/4U) was higher than the other treatments with no significant difference between above three treatments during booting to late grain filling stage. While leaf nitrogen content for treatments of biogas slurry N as topdressing fertilizer (1/2U +1/2B, 3/4U +1/4B and 1/2B +1/2B) was lower than those treatments of urea N as topdressing with lowest in treatment of single biogas slurry application. The C/N ratio in flag leaf showed a "U" shaped trends with growth stages, with high at jointing and middle filling stage, low from booting to the early filling stage. C/N of treatments of biogas slurry as dressing was higher with highest in biogas slurry N only, and that of treatments of urea N as topdressing was lower with lowest in urea N only. Flag leaf SPS and GS activity showed a single peak curve with growth process with maximum at flowering stage. SPS activity were higher in treatments of 1/4B +3/4U and 1/2B +1/2U, and lower in treatments of chemical N as basal fertilizer and biogas slurry N as topdressing fertilizer with lowest for the treatment of biogas slurry N only. The GS activity was higher in treatments of 3/4U +1/4B and 1/2U +1/2B, and lowest in the treatment of urea N only. Plant N accumulation in wheat was the highest from booting to heading stage, and changes steadily from flowering to maturity. Plant N accumulation was the highest in the treatment of 3/4U+1/4B and lower for those treatments of 1/2U +1/2B, 1/4B +3/4U and 1/2U +1/2U.4. Grain yield in the treatment of 1/4B+3/4U was the highest among treatments with significant difference between the two treatments of 1/4B+3/4U and 1/2B+1/2U. Grain yield in the treatment of biogas slurry N only (1/2B+1/2B) significantly decreasing because of plant malnutrition with poor chlorophyll fluorescence parameters and Pn. The treatment of 1/4B +3/4U generating highest yield increased by 6.87% and 28.74% than the single application of urea fertilizer and biogas slurry. The viscosity parameters in the peak viscosity as the final viscosity, breakdown and setback values were the highest in the treatment of 3/4U +1/4B, and was lowest in the treatment of urea N only. Gelatinization temperature was lowest in the treatment of 3/4U +1/4B with no significant difference between the other treatments. The total protein content was the highest in the treatment of 1/2U +1/2B, with second for the treatment of 3/4U +1/4B and the lowest value in the treatment of biogas slurry N only. There was the highest value for globulin, gliadin and glutenin contents in 1/2U +1/2B and for albumin content in 3/4U +1/4B, and the lowest for all sorts of protein content in 1/2B +1/2B. Stretch parameters under different treatment conditions changes greatly with the highest values in 3/4U +1/4B for development time, stability time, FQN, tensile area, tensile resistance and its ratio, being followed by 1/2U +1/2B and 1/2U +1/2U, the lowest in 1/2B +1/2B, and the degree of softening performance contrast trend. While the extensibility was the highest in 1/2B +1/2U, with relative low for 1/4B +3/4U and 1/2B +1/2B.