Effects Of Organic Fertilizer And Nitrate Residues Of Spring Rapeseed In Qinghai Province

Spring rapeseed has a long history of planting in Qinghai Province.At present,the planting area has reached 140,000 hectares,accounting for about 1/3 of the total crop area in the province.Rapeseed needs a large amount of fertilizer and can tolerate chemical fertilizers.Fertilization is the main factor affecting rapeseed quality and yield,but excessive fertilization not only does not benefit the growth of rapeseed,but also may cause many environmental problems.What is the status of fertilizer application in spring rapeseed in Qinghai? Is there excess fertilization? Can chemical fertilizers be reduced without reducing production? What is the potential of fertilizer reduction? Based on a large number of surveys by farmers,this study used a hybrid rapeseed “Qingza 6” as a test material and arranged a two-year field experiment in Huzhu County of Qinghai Province to study the amount of nitrogen applied to the soil under different organic fertilization conditions.The effects of spring rapeseed growth,yield,nitrogen fertilizer use efficiency,and soil nitrogen residuals were clarified to clarify the potential for reducing nitrogen and increasing efficiency of spring rapeseed.The study obtained the following main results:(1)After surveying 400 growers in three spring rapeseed planting counties in Huzhu,huangzhong and Datong,it was found that 87.3% of the farmer's spring rapeseed production exceeded the average annual spring rapeseed yield(1674.17~2158.36 kg/hm2).Compared with the local recommended fertilization amount,30.0% of the farmers had a moderate nitrogen fertilizer input,40.7% were high and very high,and 29.3% were low and very low;Farmers accounted for 37.4% of the farmers with appropriate input of phosphate fertilizer,32.8% for high and very high,and 29.7% for low and very low.The amount of potash fertilizer and organic fertilizer is extremely low,and the input of medium and trace fertilizers is basically blank.Compared with the results of the 2009 and 2010 surveys,the level of nitrogen application by farmers has generally declined.The proportion of farmers with low phosphorus application has decreased slightly,but the proportion of rural households with high phosphorus application has increased.(2)In the field with higher fertility,compared with no organic fertilizer,application of 3 t/hm2 organic fertilizer did not significantly increase the yield of spring rapeseed in the current season,but the apparent utility rate of nitrogen fertilizer had an increasing trend,0-60 cm soil Nitrate residue remained significantly lower.(3)Under high fertility soil conditions,compared with no nitrogen application,nitrogen fertilizer 80kg/hm2 increased yield by 23.1%;compared with local recommended nitrogen application rate of 160kg/hm2,nitrogen fertilizer application of 80kg/hm2 increased yield by 10.6%,and nitrogen fertilizer utilization rate increased by 22.6%.,Soil nitrate residue decreased by 22.9%.The yield of spring rapeseed in low fertility soil has obvious response to the amount of nitrogen fertilizer.With the increase of nitrogen application rate,rapeseed grain yield increased significantly.The grain yield reached the highest of 2461.54 kg/hm2 in N120 treatment,which was 41.18% higher than that of N0 treatment and 82.28% higher than that of ck treatment.Compared with the local recommended nitrogen application rate of 160 kg/hm2,N120 treatment increased production by 13.39%,nitrogen fertilizer utilization rate increased by 38.5%,and soil nitrate nitrogen residue in 0-60 cm soil decreased by 11.3%.In summary,the spring rapeseed yield in Qinghai is stable all the year round,and the total nitrogen application rate is declining.However,there are still more than 40% of rural households with high nitrogen application rates;the overall phosphorus application rate is increased;the input of organic fertilizers and trace element fertilizers is very low..Application of organic fertilizer had no significant effect on the yield of rapeseed in the current season,but it had the effect of increasing the apparent utilization rate of nitrogen fertilizer and reducing the residual amount of nitrate in soil.Under high fertility conditions,the N application rate can be reduced by 50% on the basis of the local recommended N application rate,and the N application rate can be reduced by 25% on low fertility soils.This will ensure a higher rapeseed yield,significantly reduce residual soil nitrate after harvest and increases nitrogen fertilizer utilization.