| It provides a theoretical basis for determining the amount of chloride-containing fertilizers to be applied to chloride-sensitive crops and to soils of different textures in rainfed areas.In this experiment,soil column simulations were used to study the distribution of exogenous Cl-leaching efficiency and residual Cl-in the soil tillage layer for different soil textures（clay loam,loam,sandy loam and sandy soil）with different rainfall amounts（55 mm,110 mm,220 mm and 440 mm）.The accuracy of the equations relating soil chloride content to rainfall and chlorine application in the simulations was also verified using field experiments.The effect of chlorine application on the nutrient content of the cultivated soil and the amount of Cl-residue on potato yield was also determined.The results showed that:（1）Soil texture affects Cl-leaching rate and leaching efficiency:Exogenous Cl-leaching from soils began at rainfall amounts of 66 mm（sandy soil）,77 mm（loam and sandy loam）,and 88 mm（clay loam）.Cl-leaching rate reached a maximum of 393.9-507.5 mg·mm-1·m-2 at 110 mm（sandy soil）and 132 mm（clay loam,loam,and sandy loam）,the cumulative rate of Cl-leaching reached92.2-92.9%at 220 mm（sandy loam and sandy soil）and 264 mm（clay loam and loam）,the correlation coefficients between Cl-leaching and rainfall reached 0.913-0.958（P<0.05）.（2）The distribution of Cl-in soils within 55-220 mm rainfall is influenced by soil texture:When the rainfall was 55 mm,the exogenous Cl-was mainly concentrated in the 10-30 cm soil layer.When the rainfall was 110 mm,the Cl-content of different soil textures was 20-30 cm>10-20 cm>0-10cm,and the higher the sand content of the soil,the higher the Cl-content in the 20-30 cm soil layer.When the rainfall was 220 mm,the Cl-content in the sandy loam and sandy soil only was not significantly different from the non-chlorine treatment,while the Cl-content in the 10-20 cm and20-30 cm soil layers was still significantly higher than that in the 0-10 cm soil layer（P<0.05）because the clay loam and loam soil did not reach the maximum leaching rate.At 440 mm rainfall,all treatments reached the maximum leaching rate,and there was no significant difference in Cl-content between chloride-treated and non-chloride-treated soils.（3）Model application of field trials to validate calculated values of soil Cl-content:In the rainfall range of 55-220 mm,large amount of Cl-leaching occurred in all the four textured soils.In this rainfall range,the fitted equations for estimation of Cl-content in soil by rainfall and chlorine application in Suihua loamy soil.It was verified that the error range between soil Cl-content and actual soil measurements in the field was in the range of[-21.8%,25.1%].Therefore,the amount of Cl-residue in soil can be estimated based on the actual rainfall and chlorine application,or the amount of chlorine-containing fertilizer application can be determined based on the local historical rainfall and the threshold value of chlorine tolerance of crops.（4）Chlorine application affects soil inorganic nitrogen content:Cl-inhibits soil nitrification.Chlorine application was positively correlated（P<0.05）with NH4+-N content in soil and negatively correlated（P<0.05）with NO3--N content and apparent nitrification rate in soil.The effect on nitrification was lost when the chlorine content in the soil was below 16.7 mg/kg.The time of appearance of maximum soil apparent nitrification rate was related to chlorine application,and the maximum apparent nitrification rate of non-chlorinated soil reached 47.0%at the 52 d.The apparent nitrification rate of chlorinated soil was 31.2-42.3%at the 52 d,and the maximum apparent nitrification rate of chlorinated soil appeared after 52 d.The application of chlorinated fertilizers at different times had no significant effect on soil Available P and Available K content.（5）Period of application and application rate of fertilizers containing chlorine have different effects on potato yield:Total yield and commercial potato yield were 5.8%and 4.5%higher than the control at 28 kg/ha（KCl dosage of 62.5 kg/ha）for basal fertilizer application,and further increase in the amount of chlorinated fertilizer would lead to yield reduction;total yield and commercial potato yield were higher than the control at 28-56 kg/ha（KCl dosage of 62.5-125 kg/ha）for follow-up fertilizer application,while total yield and commercial potato yield were significantly higher than the control at 84-112 kg/ha（KCl dosage of 187.5-250 kg/ha）for follow-up fertilizer application（P<0.05）.The total yield and commercial potato yield were higher than the control at28-56 kg/ha（KCl dosage of 62.5-125 kg/ha）,while the total yield and commercial potato yield were significantly higher than the control at 84-112 kg/ha（KCl dosage of 187.5-250 kg/ha）（P<0.05）.The maximum yield,commercial potato yield and starch yield were reached at 84 kg/ha（KCl dosage of187.5 kg/ha）.This experiment was conducted to estimate the amount of Cl-residue in soil based on rainfall and chlorine application,or to determine the amount of chlorine-containing fertilizer application based on local historical rainfall and crop chlorine tolerance threshold,as well as to provide scientific reference for the safe application of chlorine-containing fertilizers to chlorine-sensitive crops. |
