| Potato is the fourth food crop in the world as well as a crop that was developed earlier than many other crops. And the area of potato production of China is the largest in the world. However, the study on the application of potato is lagged, the application and popularization of the practical technology is relatively poor, and the unit yield is relatively low, when compared with that of the major food crops such as rice and wheat.Lichuan City, located in the hinterland of Wuling Mountain area and belonged to Southwest Mountain area, is a mixed agricultural area of potato production with single-cropping and double-cropping. The maximum elevation here is2041m, and the minimum altitude is316m, with an average elevation of1100m. The soil here is mostly yellow brown soil, which is with deep and loose soil layer. The annual average temperature here is12.8°C, the relative humidity is80%-85%, and the average annual rainfall is1400mm. This area is with cold and cool climate, abundant rainfall, little sunshine and unique ecological environment, which is suitable for potato growth. What’s more, high altitude mountain area is with low aphid density and good natural isolation condition, so it is conducive to the multi-quarter application of seed potato. The annual potato acreage of this place has remained in26.67kha. The unit yield is15000kg/hm2, lower than that of the average level of the whole world (16005kg/hm2), and is with significant difference between the inter-annual. Studying problems stated as above and finding out the main reason will promote potato production in Lichuan, and provide a reference for the development of potato production in Wuling Mountain area.This study was focused on main extensional potato varieties of Lichuan City, planting density, disease control and fertilizer application in the production of potato. And targeted investigation and research were conducted combined with local meteorological data. Some conclusions were made as followed:(1)There exist some technical problems in the current potato production of Lichuan City such as with no main cultivars but a variety of cultivars, weak control of late blight and no technical system that own good resilience to hazards.The potato cultivars that are planted with relatively larger scale are E-potato No.5. Mira, and E-potato No.3. but none is planted with an acreage rate less than50%. The planting area of E-potato No.5is the largest, but accounting for only42.1%of all potato planting acreage, followed by that of Mira (accounting for about37.5%) and that of E-potato No.3(accounting for about14.1%). And the survey of10potato cultivars in the place showed that the mixing rate in the field of different cultivars is averagely26.3%.There are85.6%of farmers doing nothing about the control of potato late blight,64.8%of households considering chemical control is invalid, only14.4%of households doing chemical control and only0.7%of farmers knowing what farm chemicals to use and how to use them.The existing potato cultural technology system is with no strong resilience to hazards. The recession of potato resistance and the loss of chemical control effect are progressive, so it does not cause significant fluctuations in the yield of potato. However, when unusual weather comes and break the prevention capability of original technology, it will lead to a large decrease of the yield in a large area.(2) In the area with an altitude below800m of Lichuan, it is appropriate to select early maturing variety-Nanzhong552, and the proper planting density is37500to45000holes/hm2. While in the area with an elevation above800m, it is appropriate to select late maturing varieties—E-potato No.5, Mira, and E-potato No.3, and the proper planting density is30015to37500holes/hm2.(3) According to the study on the fertilization effect of potato with pilot demonstration, the abundance and deficiency index of nutrient in the potato planting soil was initially set as below (test value of conventional methods).Serious lack:soil nitrogen (N)≤50mg/kg, soil available phosphorus (P)—6.0-15.0mg/kg, available potassium (K)—60-120mg/kg; lack:soil nitrogen—50-100mg/kg, soil phosphorus (P)≤6.0mg/kg, soil available potassium (K)≤60mg/kg; latent lack:soil nitrogen (N)>100mg/kg, soil available phosphorus (P)>15.0mg/kg, available potassium (K)>120mg/kg.(4) According to the abundance and deficiency index of nutrient in the potato planting soil in Lichuan and the target of potato production, the application index of fertilizer was initially set as follows.Serious lack:nitrogen (N)—202.5kg/hm2, phosphate (P2O5)—75kg/hm2, potash (K2O)97.5kg/hm2; lack:nitrogen (N)—172.5kg/hm2, phosphate (P2O5)—60kg/hm2, potash (K2O)—75kg/hm2; latent lack:nitrogen (N)—142.5kg/hm2, phosphate (P2O5)—45kg/hm2, potash (K2O)52.5kg/hm2.(5) Compared with conventional fertilization, formula fertilization saved33kg/hm2nitrogen,3kg/hm2P2O5and87kg/hm2total nutrients. But it also added57kg/hm2K2O. That’s to say, this method reduced the use of (N content—46%)72kg/hm2urea,25.5kg/hm2calcium superphosphate (P content—12%) and3kg/hm2total fertilizers. And it added94.5kg/hm2potassium chloride (K content-60%).(6)The yield of potatoes with soil testing and fertilizer recommendation was1273.5to2997kg/hm2more than that of potatoes with conventional fertilization, with an average value of2149.5kg/hm2, and the increasing rate is3.8%to30.8%. with an average value of10.2%. The output increased849to1995yuan/hm2. with an average value of1558.5yuan/hm2. The cost of fertilizer increased409.5to537yuan/hm2, with an average value of505.5yuan/hm2. The net income increased894to2587.5yuan/hm2, with an average value of1987.5yuan/hm2. The ratio of output to input is3.36:1to7.323:1, with an average value of5.8:1. This method showed significant increase in the yield of potato and in nutrient utilization rate.(7) The calculation of this pilot demonstration showed that the seasonal utilization rate of nitrogen, phosphorus and potash fertilizer was53.8%,12%and43.6%, respectively, when using the method of soil testing and fertilizer recommendation. But the application of potash fertilizer increased compared with conventional fertilization.(8)To control potato late blight in Lichuan, we should select one of chemicals among Infinito, Equation, Dimethomorph, and Kelu with standard dose to prevent potatoes from late blight, and select one of them among the first three chemicals with standard dose to control the disease after7-10days, under the premise of choosing disease-resistant cultivars and strengthening field management(9)The control effects of52.5%Equation,68.75%Infinito and50%Dimethomorph are equivalent, nearly80%, and all work in2to4stage. So they can control potato late blight effectively and can be used alternately. Although the effect of72%Kelu is worse than that of the three chemicals with relative doses mentioned above, nearly50%, its effect can last relatively long. So it can be used as one of chemicals to prevent potatoes from late blight. |
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