| Ganzhou city in Jiangxi province in south China is a predominant region of naval orange production, and plays an important role in citrus production in China. With the development of the navel orange industry of this region, it is imperative to find out the site conditions and planting actuality. In addition, leaf yellowing is a symptom of boron deficiency occur in main local cultivar’Newhall’navel orange grafted on Trifoliate orange. Thus, we investigated the soil type, orchards altitude, planting slope, the varieties, planting time, planting density and2005-2008annual output; We collected1275soil samples in478navel orange orchard in Ganzhou to analyze the condition of soil B. Furthermore, a trail experiment was conducted during2008-2011with applied B in first two years and then stopped fertilizing B to investigate the dynamic changes of B content in leaves and the B fertilizer aftereffect. Meanwhile, a hydroponic experiment was conducted to figure out the effects of B deficiency and excess on Trifoliate orange. The main results are as follows:1)82.1%of the soil type is red soil in the southern of Jiangxi.85.0%of the Navel orange orchards are at an elevation of100-300m.69.3%of the Navel orange orchards are at a slope of10-30°. Newhall navel orange has the largest amount of acreage, over85%of the total acreage. Planting time of the most navel orange is2005-2008, and most navel orange orchards are newly planted in the last5-8years.59.7%of the most navel orange orchards have a density of55-83plants per667m2.2) Boron deficiency of navel orange orchards in the southern of Jiangxi is serious, and the B deficiency proportion is87.1%. The average content of available B in soil is0.16mg/kg. Longnan county has best B status in this investigation, and its average soil available B content is0.26mg/kg. However, there are still64.7%navel orange orchards in this county lack of B in soil. Boron deficiency in Zhanggong is the most serious. Its average content of available B in soil is0.09mg/kg, and the B deficiency proportion is over95.6%. Average content of available B in soil of the three most production county Xinfeng, Xunwu, and Anyuan are0.18mg/kg,0.16mg/kg, and 0.15mg/kg, and the B deficiency proportions are77.3%,86.2%, and91.7%separately.3) Results of the B fertilizer experiment showed B content in new leaves of spring shoots was higher when applied with B fertilizer. During2008-2011, B content in new leaves of spring shoots was in an appropriate level with B applied, whereas it was in the level of B deficiency without B applied. There was no significant difference between with and without B supply in the new leaves of fall shoots two years after B supply stopped. B content in old leaves after two consecutive years of B supply was232.6mg/kg, which indicated that consecutive of B supply might cause excessive accumulation of B in old leaves.4) Boron deficiency could cause the inhibition of the seedlings growth include shoot and root. Boron deficiency caused visible symptoms of roots grey color, apical enlargement, lateral root number increased near the apical, and decreased in the total root tips, and significantly reduce the number and length of fine roots. The number of the coarse roots was affected little.5) The results showed that the seeding height, the number of leaves and the dry weight decreased with increasing B supply. Leaves yellowing occurred in all the B treatments without B0. Bound B content in root and shoot were higher than semi-bound B and free B, whereas the free B content in leaves was higher than bound-B and semi-bound B. Bound B and semi-bound B had little changes in roots and stems with various B treatments, but free B in leaves significantly increased as leaf chlorosis aggravated, indicating that leaf chlorosis was closely related with free B in leaves, which might be one of the boron nutrition diagnostic indicators on trifoliate orange. |
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