| Gansu province is one of the potato producing areas in our country,the potato industry in gansu province occupies an important place in the agriculture and rural economy.However,farmers in pursuit of high yield,the phenomenon of blind fertilizing is becoming more common, not only caused the waste of fertilizer resources,but also caused serious environmental pollution.Aimed that,a field expriment was conducted at Dingxi Extension of Gansu Province, aimed to understand the effects of nitrogen level on growing stages,dry matter accumulation and distribution and the nitrogen recovery efficiency.The aim of the study was to improve fertilizer management in potato production.Rainfed cropland and Irrigated cropland experiments were carried out,and six treatments of every field expriment were set up using completely the randomizde block design with four repeated,in cluding T1,0 kg N/hm2;T2,50 kg N/hm2;T3,100 kg N/hm2;T4,150 kg N/hm2;T5,200 kg N/hm2 and T6,250 kg N/hm2 in Rainfed cropland;and T1,0 kg N/hm2;T2,75 kg N/hm2;T3,150 kg N/hm2;T4,225 kg N/hm2;T5,300 kg N/hm2 and T6,375kg/hm2 in Irrigated cropland。The results are as follows:1.Different nitrogen rates have significantly affected on dry matter accumulation.the sourc organ growth deficiency due to insufficient nitrogen,but excessive nitrogen caused source sink relationship imbalance and with the increase of nitrogen, Vmean decreased and Δt increased, which indicates that the nitrogen amount too much or too little will effect Vmean and Δt,and this is the main reason of the whole plant dry matter accumulation and tuber yield changes.And this preformance in accumulation of dry matter of whole plant and different organs of harvest period, compared with the CK,rainfed cropland T2-T6 treatment the whole plant dry matter increased 5.36% ~-21.04%,T2-T6 tuber dry matterr increased 2.66% ~-26.06%;irrigated cropland T2-T6 treatment the whole plant dry matter increased 1.51% ~12.57%, T2-T6 tuber dry matter increased 0.11% ~ 17.14%.The correlation analysis showed that rainfed cropland and irrigated cropland tuber yield,tuber weight and whole plant and each organ dry matter had significant linear correlation,and negative correlation between the Ratio of root to shoot,potato whole plant dry matter accumulation is sufficient tuber yield mainly.2. We also found nitrogen rates had significant effect on dry matter distribution of potato plant across fertilization treatment.on the one hand, the amount of nitrogen insufficient cuese decrease of leaves dry matter distribution proportion,while with the amount of nitrogen increase,more dry matter distribution proportion of stems and leaves;on the other hand,showing scissors differences(SD) and dry matter balance points(BP).SD was the inportant indicator of tuber yield.Our study show T2 had the highest SD size in rainfed cropland and T4 had the highest SD size in irrigated land,this indicat that 50 kg N/km2 in rainfed cropland and 150 kg N/km2 in irrigated land can stimulate the distribution of dry matter tored in vegetative organ during pre-anthesis into tuber in later development stage.With the increase of N application rate,the potato growth stage has a tendency to delay,compared with CK,the dry matter balance points of T2- T6 treatment delay 2-16 days in rainfed cropland,and in irrigated cropland T2- T6 treatment delay 7 days,and with the more N application the more number days delay.3.N application rates have significantly effcet of the potato tuber protein content,with the increase of N application,the protein content increased of rainfed cropland and irrigated land potato tuber,compared with CK,the protein content increased by 13%,28%,25%,36% and 38% of irrigated land T2- T6 treatment,and increased by 33%,40%,44%,40% and 49% in irrigated land;In the rainfed cropland and irrigated land,the N appily rate had no significant effect of potato tuber Starch content;Soluble sugar and Reducing sugar content in potato tuber is unimodal trend with the increase of N application rate changes.4.N application rate on potato yield and economic benefits have a significant effect,with the increase of N rate,the tuber yield all showed a trend of unimodal trend in rainfed cropland and irrigated land.In rainfed cropland,compared to CK,T2- T6 treatment yuber yield increased 17.86%,6.43%,17.39%,17.39% and 27.86%,and T2- T6 treatment net income increased by 15.26%,10.27%,27.61%,27.61% and 43.62%; In irrigated land,T2- T6 treatment tuber yield increased by 0.58%,3.47%,13.46%,0.58% and 3.29%,and T2- T6 treatment net income increased by 0.12%,2.90%,10.25%,3.63% and 9.32%;Nitrogen had no significant effect of commodity rate on rainfed cropland and irrigated land.5.The nitrogen concentration of different organs of potato changes with the change of growth stage,but the nitrogen concentration of different organ is always leaf > stem > root > tuber,during the reproductive period,leaf,stem,root and tuber nitrogen concentration changes in the range of 2% ~ 5%,1% ~ 4% and 1% ~ 3%,1% ~ 3%.Rainfed cropland, the utilization rate of nitrogen fertilizer,phosphate fertilizer and potash fertilizer showed a downward trend with the increase of N application,the range of change is 50.73%- 10.94%, 13.99%- 0.64% and 39.68%- 2.60%;In irrigated land, nitrogen fertilizer,phosphate fertilizer and potash fertilizer absorption utilization rate showed a unimodalcurve with the increase of N application rate,the range of change is 20.92%- 6.76%,9.32%- 2.12% % and 22.50%- 1.73%.In rainfed cropland and irrigated land,the N harvest index showed a unimodal curve,T2 treatmet was highest in dryland and T4 treatment was highest in irragated land, irrigated with T4 treatment highest,but there was no significant effect.This study results show that appropriate N application rate is not only beneficial to the potato growth and development of different organs and built,and can improve effective distribution of dry matter,at the same time also can improve the fertilizer utilization ratio.Under this experimental condition,when the aim yield is 1.65 t/667m2,the recommended amount of nitrogen application is 50 kg/hm2 in dryland and 225kg/hm2 in irrigated land. |
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