| Recently, the excessive use of chemical fertilizer (especially nitrogen and phosphorus fertilizers),unbalanced application of nitrogen, phosphorus and potassium, irrational application (excessive orinsufficient) of organic manure, and improper fertilization methods led to some serious problems, suchas degradation of soil fertility, low fertilizer use efficiency, negative impact on environment anddecreasing safety of vegetable products in main greenhouse vegetable production regions in China.Little information is available on the effect of different fertilization patterns on NH3volatilization,nitrous oxide (N2O) fluxes, and nutrient leaching loss from greenhouse vegetable soils. Scientificevaluation of nutrient balance in soil-greenhouse vegetable system is very helpful for improving soilfertility management. This study was conducted to determine the effect of combined application oforganic manure and chemical fertilizers on ammonia volatilization, N2O emission, nutrient leaching,soil fertility, nutrient uptake by vegetable (celery-tomato rotation), and vegetable yield undergreenhouse condition in Tianjin from2009to2011. The field experiment consisted of eight treatments:1) No N,2)4/4CN, all nitrogen in chemical fertilizer (CN),3)3/4CN+1/4nitrogen in organicmanure(PN),4)2/4CN+2/4PN,5)1/4CN+3/4PN,6)2/4CN+1/4PN+1/4nitrogen in straw (SN),7)2/4CN+2/4SN and8) CF, conventional fertilization. Equal amount of N, P and K was used fortreatments2,3,4,5,6and7and same rates of P2O5and K2O were applied for treatments1,2,3,4,5,6and7. Soil NH3volatilization, N2O emission and nutrient leaching loss was measured by the ventingmethod, static chamber-gas chromatograph method and a lysimeter device method with undisturbed soillayers. The main results obtained are summarized as follows:1. Effects of combined application of organic manure and chemical fertilizers on ammoniavolatilization from greenhouse vegetable soilThe peak of NH3volatilization rate occurred within2～3days after basal fertilization, whereas infirst day after fertilizer top-dressing (fertilization and irrigation were carried out simultaneously) duringthe celery and tomato growth period. Thereafter, the NH3volatilization rate from the nitrogenapplication treatment decreased and closed to the similar level from the no nitrogen applicationtreatment8～10days after basal fertilization and10～11days after fertilizer top-dressing. The NH3volatilization was significantly affected by temperature and exhibited obviously seasonal variationsduring the celery and tomato growth period. Significant correlations between the NH3volatilization andsoil temperature in5cm soil layer during the celery and tomato growth period were generally observed,with correlation coefficients ranging from0.37to0.67.Total NH3volatilization during tomato growthperiod with higher temperature was notably higher than that in celery season, with the total amounts ofNH3volatilization for all treatments in tomato season being3.0times of that from the celery growthperiod. Compared with the conventional fertilization with much higher rates of fertilizers, the combinedapplication patterns of organic manure and chemical fertilizers significantly decreased the total NH3volatilization by50.0%and47.9%during the celery and tomato growth period, respectively. Strawapplication compared with pig manure application with the same N rate respectively decreased the NH3 volatilization by32.4%and30.0%during the growth period of celery and tomato under thisexperimental condition.2. Effects of combined application of organic manure and chemical fertilizers on N2Oemission from greenhouse vegetable soilThe peak of N2O emission flux occurred within5～7days after basal fertilization (1～3days afterirrigation), whereas within1day after fertilizer top-dressing (fertilization and irrigation were carriedout simultaneously) during the celery and tomato growth period. The N2O emission fluxes from thenitrogen application treatments were close to the flux from the no nitrogen application treatment20days after basal fertilization (15～16days after irrigation), whereas11days after fertilizer top-dressing.40%～65%of total N2O emissions during celery or tomato growth period occurred from the first20days after basal fertilization. The N2O emission fluxes were greatly affected by irrigation during thegrowth period of celery and tomato, with the fluxes gradually decreasing after basal fertilization, thenrapidly increasing after irrigation. Significant correlations between the N2O emission fluxes for alltreatments and soil moistures were observed, with correlation coefficients ranging from0.43to0.72.The N2O emission was significantly affected by temperature, and exhibited obviously seasonalvariations during the celery and tomato season. Significant correlations between the N2O emissionfluxes for different treatments and soil temperatures in5cm soil layer during the celery and tomatogrowth period were generally observed, with correlation coefficients ranging from0.40to0.58. TotalN2O emission during tomato growth period with higher temperature was higher than that during celeryseason, with the total amounts for all treatments in tomato season being3.1times as high as that of thecelery growth period. Compared with the conventional fertilization with much higher rates of fertilizers,the combined application patterns of organic manure and chemical fertilizers significantly decreased thetotal N2O emissions by66.3%and85.1%as well as loss ratio of N fertilizer by45.2%and74.9%during the celery and tomato growth period, respectively. Straw application compared with pig manureapplication with the same N rate respectively decreased the N2O emission by43.4%and74.2%duringthe growth period of celery and tomato under this experimental condition.3. Effects of combined application of organic manure and chemical fertilizers on soil nutrientleaching loss under greenhouse conditionCompared with treatments of all NPK applied with chemical fertilizer and the conventionalfertilization treatment, the combined application patterns of organic manure and chemical fertilizersdecreased total N leakage rate in the leakage water by29.6%and54.5%, and NO3--N leakage rate inthe leakage water by33.0%and55.7%, respectively. Compared with the conventional fertilization, thecombined application patterns of organic manure and chemical fertilizers decreased NH4+-N leakagerate in the leakage water by59.8%. NO3--N leaching loss accounted for almost80%of total nitrogenleakage rate during four growth seasons. Compared with the conventional fertilization, the combinedapplication patterns of organic manure and chemical fertilizers decreased total P and total K leakage rate,respectively. Nitrogen leaching loss was identified as significant sources of leaching loss in soilnutrients (N, P and K) under greenhouse condition. The average leakage rates of nitrogen (N), phosphorus (P) and potassium (K) for all treatments were37.2,0.114and1.45kg/ha. Combinedapplication patterns of organic manure and chemical fertilizers with the same NPK rate significantlydecreased nitrogen (Total N, NO3--N and NH4+-N) leakage rates in the leakage water.4. Effects of combined application of organic manure and chemical fertilizers on soil fertilityunder greenhouse conditionSoil nitrate contents generally tended to increase from surface soil layer (0-20cm) to deep soillayer after celery harvest, whereas increase in surface soil layer and decrease in deep soil layers aftertomato harvest. Compared with the conventional fertilization, the combined application patterns oforganic manure and chemical fertilizers significantly decreased NO-3-N contents in soil layers of0-20,20-40,40-60,60-80and80-100cm by34.5%,44.9%,44.7%,40.2%and34.6%, respectively. Soilavailable P generally tended to decrease from surface soil layers to deep soil layer after celery andtomato harvest. Compared with the conventional fertilization, the combined application patterns oforganic manure and chemical fertilizers decreased available P contents in soil layers of0-20,20-40,40-60, and60-80cm by21.0%,21.6%,21.1%and21.7%, respectively. The combined applicationpatterns of organic manure and chemical fertilizers significantly increased soil OM contents by8.5%,12.2%,17.5%and24.5%(averaged15.7%for four growth seasons) than that with treatment of all NPKapplied with chemical fertilizer after celery and tomato harvest.5. Effects of combined application of organic manure and chemical fertilizers on vegetableyield, qulity and nutrient uptake under greenhouse conditionCompared with the conventional fertilization with much higher rates of N, P2O5and K2O, there arenot significant differences of celery and tomato yields under the different combined application patternsof organic manure and chemical fertilizers with proper rates of N, P2O5and K2O. Income of thecombined application patterns of organic manure and chemical fertilizers was significantly increased.Compared with treatments of all NPK applied with chemical fertilizer and the conventional fertilizationtreatment, the combined application pattern of3/4N in chemical fertilizer and1/4N in organic manureincreased yield by4.8%and5.1%, and increased income by9351and28431RMB yuan/ha,respectively. Compared with treatments of all NPK applied with chemical fertilizer and the conventionalfertilization treatment, the combined application patterns of organic manure and chemical fertilizersdecreased nitrate contents in edible parts of vegetable by11.3and19.1%, respectively. Whereas thecombined application patterns of organic manure and chemical fertilizers increased Vc contents inedible celery parts and fruit of tomato by32.6%and6.5%, respectively, than that in treatment of allNPK applied with chemical fertilizer. Compared with the conventional fertilization, there are notsignificant differences of celery and tomato nutrient (N, P2O5and K2O) uptake under the differentcombined application patterns of organic manure and chemical fertilizers with proper rates of N, P2O5and K2O. The average plant uptake of N, P2O5and K2O for producing1000kg products were1.91,0.96and5.47kg for celery, and2.33,0.83and4.68kg for tomato, respectively. The average uptake ratio ofN, P2O5and K2O was1:0.52:2.93for celery, and1:0.36:2.02for tomato.6. Nutrient balance in soil–greenhouse vegetable system under the combined application patterns of organic manure and chemical fertilizersNutrient application with both chemical fertilizer and organic manre was the main source ofnutrient input, accounting for more than95%of the total nutrient input. Crop nutrient uptake wasprimary nutrient output, with N, P2O5and K2O uptake accounting for49.1%,34.6%and94.3%of totalN, P2O5and K2O input, respectively. Moreover, the average N leakage rate accounted for7.7%of totalN input, whereas P or K leakage rate only contributed less than1%of the total P or K input. NH3volatilization and N2O emission contributed less than5%of the total N input. Compared with theconventional fertilization, the combined application patterns of organic manure and chemical fertilizersdecreased the annual N, P2O5and K2O surpluses rate by71.7%,75.4%and90.0%, respectively. Theannual N and P2O5surpluses in the soil–greenhouse vegetable system still exceeded its rational range.Application of P and K fertilizers in the soil–greenhouse vegetable system should be improved bybalanced fertilization to rationalize P and K status. The proper pattern of combined application oforganic manure and chemical fertilizers based on yield, income and environment during a short periodwas the pattern of combined application of3/4N in chemical fertilizer and1/4N in organic manureunder this experimental condition.
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