| Ammonium bicarbonate(ABC)with the chemical formulation NH4HCO3 is a unique nitrogen fertilizer in China in terms of the needs in agricultural production and economic and technical situation since 1960s.In addition to its cheap character,ABC is also environment-friendly,which does not deteriorate soil quality after long-term application,and thefinal products of(NH3,CO2,H2O)ABC are the essential elements for plant growth.However,some drawbacks of ABC exist,for examples,unstable at normal temperature,single nutrient,and low nitrogen content(17.1%).This paper was aimed to resolve the drawbacks of ABC.We firstly presented new thought and new technolgies in modification of ABC,and then developed a new type of fertilizer that is called as multielement long-acting granular ABC(MLGABC).Afterwards,both pot and field experiments with wheat and corn were conducted to biologically evaluate the new fertilizer product.Main results and conclusions were obtained as follows:1.Using ABC as the main raw material,matched with a moderate amount of urea,ammonium composite stabilizer and anticaking agents,MLGABC was prepared by extruding granulation at room temperature without any addion of binder or water.Thus the technology is characterized by simple process,low cost,low energy consumption,short production cycle,non-pollution,and thus high economic benefit.The new product not only overcame the disadvantages of ordinary ABC such as single nutrient,low effective components and easy absorption of moisture and decomposition,short period to supply nitrogen and thus low utilization rate,but also had many advantages such as mutiple uniform sizes(ts and easy absorption of moisture and decompositio,high compressive strength(?19N),diversified nutrients(N,Ca,Mg,P,S,etc.),higher nitrogen content(23%or higher),long period(-100 d)to supply nitrogen,good stability and nutrient use efficiency(?45%),and beneficial to storage,transportation and application.2.Based on the principles of acting mechanisms and screening,we indentified the proper ratios of mono-ammonium phosphate,aptite and magnesium oxide to form an additive which was used to significantly promote a slow release of nitrogen from ABC after it was incoperated into ABC.This additive could dry the ABC to a great extent through chemical and physical mechanisms.The mixture(or the product)of ABC with the additive was characterised by good fluidity and granulation and also low price of materials used.Furthermore,the product(MLGABC)contained multiple nutrients and thus could increase crop yieds greater than the original ABC after applied to soils.3.This thesis also provided the national standard of MLGABC(HG/T4218-2011)and the methods for determining total nitrogen content and other components in the product,by which the errors fell into acceptable ranges.4.The process of granulation during which the product was made from a combination of ABC with the additive made the free water content decreased by 40.0%-49.8%and this significantly slowed down the nitrogen releasing rate of ABC.This could be explained by a newly produced substance(NH4MgPO4)and the transformation of free water in orginal ABC to crystalline water in the product[NH4MgPO4·6H2O(NH4HCO3)·CaSO4·2H2O(NH4HCO3)].The NH4MgPO4·6H2O and CaSO4·2H2O formed during the process wrapped or covered the ABC and thus isolated it from air and finally eliminated its reabsorption of water from air.5.Results from incubation experiments in sultion(25? and 30?)showed that the accumulated ammonium-,nitrate-and amine-N in solutions from the MLGABC or urea were increased with incubation time.MLGABC had a stadily slow release of nitrogen into solution when compared with urea.Similar results were also obtained in soil incubation experiments,showing that MLGABC indeed prolonged the nitrogen release,which could be beneficial to plant growth.6.Resultes from wheat pot experiments showed that the ear length and actual spikelet of wheat plants applied with MLGABC were 10.9%and 10.6%higher than the control,respectively and the thousand kernel weight,kernels per spike and yields of wheat plants applied with MLGABC were 14.5%,10.0%,and 14.2%higher than the control,respectively.The antioxidant enzyme activities in the leave and root of wheat plants applied with MLGABC were significantly increased compared to the control,whereas the MDA content remarkably decreased.The chlorophyll content had the same regulation to the antioxidant enzyme activities.The root biomass and root activity in different periods of wheat plants applied with MLGABC were significantly higher than the control.Meanwhile,it was found that the accumulation patterns of N and K were similar in different periods of wheat growth,in which the content of both N and K showed increase gradually,whereas the P content in filling stage of wheat plants was decreased.At maturity stage the allocation of N and P were kernel>leaf>stem and sheath applied with MLGABC,whereas that of K was stem and sheath>leaf>kerne.7.Resultes from corn field experiments showed thatnitrate reductase,SPAD,area index,photosynthetic rate and nitrogen accumulation in corn leaves in the treatment of MLGABC were higher than any other nitrogen fertilizers applied to the soils.Therefore,nitrogen recoverate rate,nitrogen agronomic efficiency and nitrogen partial factor productivity in the treatment of MLGABC were significantly higher than any other nitrogen fertilizer treatments.Therefore,the corn yield in the treatment of MLGABC was increased by 3595kg hm-2 when compared with the CK,and the net income per hectare of 4352.9 RMB.8.Resultes from wheat field experiments showed application of urea and MLGABC could significantly increase dry weight of wheat plants,total ears,kernels per spike andthe thousand kernel weight,thus realizing the increased yields and the increased N recovery rate.During the same period after flowering,the values of the SPAD,Fv/Fm,?PS ? and qP of the last first leaf of wheat plants applied with MLGABC were higher than CK.The residual efects of urea and MLGABCon the yields of next season crop(corn)were much higher than any other nitrogen fertilizer application treatments.This could be attributed to the increased kernels per spike andthe increased thousand kernel weight.The order of yield-increase potential by different fertilizers in the wheat-corn rotation system was as follows:urea?MLGABC(granulated)>cow manure together with ammonium bicarbonate>MLGABC(powder)>ammonium bicarbonate.The net income per hectare was 2843.1 RMB that was the highest among the all fertilizer treatments.As a conclusion,the thesis provided a proper ratios of mono-ammonium phosphate,aptite and magnesium oxide to form an addictive by which MLGABC product could be made,clarified the acting mechanisms of MLGABC product in which there were both chemical and hysical action,provided the data of synchronization of nitrogen supply from MLGABC product with wheat and corn plants,chanllenged the traditional theriory in which ABC could not be mixed with other chemical fertilizers.This research work had a great potential for further development of ABC,a cheapest chemical nitrogen fertilizer in China. |
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