The existing navel orange area in southern Jiangxi is 26,700 hm2, which will grow to 66,700 hm2 in 2005. At present, Gannan navel oranges are mainly distributed in Xinfeng, Anyuan, Xunwu, Dayu, Ruijin, Du Yu, Xingguo and Chongyi. Xinfeng, Anyuan and Xunwu counties account for more than 50% of the total planting area.
Gannan navel orange generally germinates in early or mid-February, and buds appear from late February to early March, and blooms in early or mid-April. It enters the first physiological fruit drop in late April, the second physiological fruit drop in early or mid-May, and the fruit expands from July to September.165438+/kloc-0 turns yellow from early to mid-June. From spring bud germination to fruit harvesting, the annual growth period is 280 ~ 300 d.
2 Suitable climatic conditions for navel orange growth and development
2. 1 temperature requirements
When the average daily temperature in spring is stable above 12.8℃, navel oranges begin to sprout. When the daily average temperature is 23 ~ 29℃, its growth and development are most suitable; 1a requires that the active accumulated temperature ≥ 10℃ should be above 5500℃. Among them, freezing injury in winter is the main meteorological disaster affecting the cultivation of navel orange in southern Jiangxi. Navel orange can tolerate a short-term low temperature of -6.5℃, but the extreme minimum temperature in winter is preferably above -3℃. The extreme minimum temperature in southern Jiangxi is -8.0℃, which appears in Chongyi. The counties (cities, districts) with extreme minimum temperature above -6.0℃ are Du Yu, Shangyou, Nankang, Xinfeng, Xunwu, Longnan, Dingnan and zhanggong district. By analyzing the frequency of extreme minimum temperature in counties in southern Jiangxi, it can be found that the frequency of extreme minimum temperature ≤-3℃ is mostly once every two years. Among them, Xinfeng and zhanggong district are the least, with an average of 6 years; Worship for righteousness is the most, and it appears almost every year. The frequency of extreme minimum temperature ≤-5℃ is relatively low, with an average of 1 1.6%, that is, 10a occurs once. Among them, there has been no extremely low temperature weather with minimum temperature ≤-5℃ in zhanggong district since 196 1, and only 1 time has occurred in Xinfeng, Du Yu and Nankang since records were recorded. The highest frequency is Chongyi, with an average of 4 years. The frequency of extreme minimum temperature ≤-7℃ is even lower, averaging 1.6%, that is, once every 60 years. Among them, Xingguo, Du Yu, Ruijin, zhanggong district, Shangyou, Nankang, Xinfeng, Xunwu, Longnan, Dingnan, etc. 10 counties (cities, districts) have never had a low temperature below -7℃ since their own data.
2.2 Precipitation requirements
Navel orange requires annual rainfall 1000mm or more. The annual average precipitation in south Jiangxi 1450 ~ 1750 mm can completely meet the requirements. However, due to the uneven distribution of seasons, floods in spring and summer and droughts in summer and autumn will affect the growth and development of navel oranges.
2.3 sunshine requirements
Navel orange is a fruit tree with strong shade tolerance, but sunshine is closely related to the high quality and high yield of navel orange. Insufficient sunshine, navel orange growth and fruit coloring are poor. The annual average sunshine hours in Gannan are 1340 ~ 1840 h, and most counties (cities) are around 1550h, which can meet the requirements of navel orange.
2.4 Comparison of navel orange producing areas at home and abroad
2.4. 1 year average temperature is higher than domestic and foreign producing areas, and the probability of freezing injury is low.
The annual average temperature in southern Jiangxi is 18.8℃, which is 0.8℃ higher than that in Zigui, Hubei, and 1.6 ~ 2.9℃ higher than that in California, USA. The lowest temperature in Chongyi is 17.9℃, the highest temperature in Du Yu is 19.6℃, and other counties (cities) are 18.3 ~ 19.4℃. The extreme minimum temperature is 2.5℃ higher than that in Zigui, Hubei, and obviously higher than that in Fengjie, Chongqing and Xinning, Hunan.
2.4.2 The precipitation is more than that in navel orange producing areas at home and abroad.
The annual precipitation in southern Jiangxi is 400~500mm more than that in Zigui, Hubei, and about 1 100mm more than that in California.
3 navel orange planting climate zoning
3. Determination of1navel orange planting climate zoning index
The climatic conditions for planting navel oranges in Gannan are superior, and there are abundant resources such as light, temperature and water, which are all suitable for the growth and development of navel oranges. By investigating the correlation between citrus yield and meteorological conditions over the years in Ganzhou City, it is found that four factors, namely, the multi-year average of extreme minimum temperature, accumulated temperature of ≥ 10℃, sunshine hours in April ~165438+average temperature in April, have the most obvious influence on navel orange production in Gannan, so it is chosen as the climate zoning index for navel orange planting in Gannan (all factors are the city average).
3.2 Data source and partition method
Based on the basic climate data of Ganzhou City1961~ 2000 * * 40 years 17 counties and stations, what is the division basis? Use1:250,000 topographic data and residential distribution data as the basic data of the whole city? The navel orange planting in southern Jiangxi was divided by using geographic information system (GIS) as a means of division and combining with the traditional climate division method.
3.3 Spatial analysis model of climatic factors for navel orange planting
Climate resources are mainly affected by altitude, latitude, topography, underlying surface properties and other factors, and there are obvious spatial distribution differences with these factors. Based on the 40-year climate data of counties in southern Jiangxi and the revised data of four mountain observation stations, the key meteorological factors and altitude of navel orange planting were analyzed by stepwise regression, and the variation law of climate factors with altitude in southern Jiangxi was obtained:
(1) The variation law of annual mean extreme minimum temperature (Tmin) with altitude (h): TMIN =? 1.3 1-0.0083h；
(2) Accumulated temperature ≥ 10℃ (? T) Variation law with altitude (h):? t = 6573.48-2.8 16h；
(3) sunshine hours in April ~ 165438+ 10 (? Variation of provincial S with altitude (h):? s = 1335.27-0. 1749h；
(4) The variation law of April average temperature (T4) with altitude (H): T4 = 20.84-0.0052 hours .. The above factors are significantly related to altitude.
3.4 navel orange planting climate zoning map making
We choose the annual active accumulated temperature and extreme minimum temperature ≥ 10℃ as the leading indicators, and the sunshine hours in April ~ 1 1 and the average temperature in April as the secondary indicators. According to the standard in table 1, the navel orange planting in southern Jiangxi was divided into four areas by means of GIS: the best area, the suitable area, the general area and the unsuitable area.
A brief description of the climatic conditions of each climatic zone
4. 1 optimal area
The region mainly includes Xinfeng, Nankang, zhanggong district, Du Yu, most parts of Ganxian and some parts of Dayu, Xingguo, Huichang, Ningdu, Shangyou and Ruijin. The elevation of this area is below 200m, with an area of about 7000km2 (including water area and road area), accounting for 18% of the total area of Gannan. The annual accumulated temperature in this area is ≥ 10℃ above 6 140℃, and the extreme minimum temperature is-4.2 ~-7.2℃. April ~165438+1October sunshine ≥ 1339h, April average temperature ≥ 19.5℃, extreme minimum temperature -4.2 ~-7.2℃, frost-free period 281~. Although the extreme minimum temperature at some stations is below -7℃, the probability of occurrence is very low, about once every 60 years. The high accumulated temperature and long frost-free period in this area have laid a foundation for the production of navel oranges with excellent color and quality in our city, and it is the most favorable area for planting navel oranges in southern Jiangxi. However, due to the low altitude in this area, most of them are used for cash crops such as rice. Therefore, when developing navel orange planting in this area, we should comprehensively consider the overall layout of agricultural structure, rationally use land resources, and achieve high quality and high efficiency. At the same time, we should also pay attention to prevent navel oranges from falling flowers and fruits seriously due to high temperature and high humidity during flowering and fruit setting in April.
4.2 Suitable areas
This area covers all counties (cities) in southern Jiangxi, mainly including Anyuan, Longnan, Xunwu, Quannan, Huichang, Xingguo, Dingnan, Ruijin, Shicheng, Dayu and Ningdu, as well as parts of Chongyi, Shangyou, Du Yu, Ganxian, Xinfeng and zhanggong district. The area is 200～300m above sea level and covers an area of about 20,000 km2 (including water area and road area), accounting for about 53% of the total area. The accumulated temperature of ≥ 10℃ in this area is 5800 ~ 6050℃, the extreme minimum temperature is -5.3 ~-7.5℃, the average extreme minimum temperature is -2.9 ~-3.6℃, the frost-free period is 280~296d, and the sunshine is 4 ~165438+/kl. The climatic conditions in this area are second only to the optimum area, and it is the main area for navel orange development. However, the extreme minimum temperature in this area is lower than that in the best area. Therefore, when developing navel orange planting, we should consider the influence of low-temperature freezing injury on navel orange, at the same time, we should comprehensively consider the overall layout of crops, try not to compete with rice fields and fertile fields, and encourage the development of navel orange planting in high-row fields and water-deficient fields to avoid disadvantages and improve the overall agricultural benefits.
4.3 General area
It mainly includes parts of counties and cities such as Chongyi, Quannan, Dingnan, Shicheng and Huichang. The elevation of this area is mostly 300 ~ 400 m, with an area of about 8000km2 (including water area and road area), accounting for about 2 1% of the total area. The accumulated temperature of ≥ 10℃ in this area is 5600 ~ 5800℃, the extreme minimum temperature is -6.0 ~-8.0℃, the frost-free period is 270~285d, and the sunshine in April is ~ 1 100 ~. Because of the extremely low minimum temperature in this area, navel oranges are vulnerable to low temperature freezing injury. Therefore, when building a garden, we should make full use of the advantages of small terrain, comprehensively consider traffic and other factors, avoid planting in low-lying cold air sinking areas and windward mouths, try to adapt to local conditions and avoid blind development.
4.4 unfavorable areas
This area is mainly distributed in the hilly and mountainous areas above 400m above sea level in Ganzhou City, with an area of about 2800km2 (including water area and road area), accounting for about 8% of the total area. The accumulated temperature ≥ 10℃ in this area is less than 5500℃, the extreme minimum temperature is below -7℃, and the frost-free period is below 270d d. Because this area is mostly hilly and mountainous, the extreme minimum temperature is low and the occurrence frequency is high, so it is not suitable for planting navel oranges.
5 Some suggestions
(1) Choose navel orange varieties according to local conditions. Because of its low probability of freezing injury and high accumulated temperature, the "best area" should choose mid-late maturity varieties, which are suitable for planting fresh fruits; "Suitable area" is the main area for developing navel oranges in our city, and the climatic conditions are second only to the optimum area, so we should choose middle-maturing varieties, among which late-maturing varieties can be considered with good microclimate conditions, mainly planting navel orange juice and processed fruits, supplemented by fresh food; Because of its high probability of freezing injury, "general area" should be developed in areas with good microclimate conditions, and early-maturing varieties are suitable
(2) Make full use of topography and microclimate to develop navel orange production in Gannan. The freezing injury of navel orange mostly occurs in the sunny night after the invasion of strong cold wave. Due to radiation cooling, cold air sinks along the hillside and accumulates in low-lying and closed places, forming a "cold lake", while there is obvious inversion (warm area) on the hillside. Therefore, citrus orchards in mountainous areas should avoid being built in low-lying and arid areas, and the slope should be less than 30.
(3) Although the annual precipitation in Gannan is more than that in other navel orange producing areas, the temporal and spatial distribution of precipitation is extremely uneven, mostly concentrated in the flood season, and it is prone to drought in summer and autumn. Therefore, all localities should also carefully consider the problems of water source and drainage and flood prevention when building gardens.