Water And Fertilizer Coupling Effects And Efficient Utilization Mechanism Of Young Apple Tree

Fruits are China's important economic crops and now become the third largest crops after food crops and vegetables, and fruit industry has the important status in the national economy. Meanwhile, Fruit industry is not only a major pillar industry of China's rural economy, but also an important channel of raising income for the national farmers in arid and semi-arid area. So, in order to explore the best mode of water and fertilizer supply of young apple tree in arid or semi-arid area and absorb the advantages of field experiment and pot experiment, we used the bucket cultivation under a mobile rainproof canopy and studied the response of growth indexes, physiological indexes, water consumption rule, soil water and fertilizer migration rule, leaf water use efficiency(LWUE), crop water productivity(CWP), irrigation water use efficiency(IWUE), partial factor productivity(PFP) of young apple tree to different water and fertilizer under the condition of water and fertilizer coupling. At last, we found the water and fertilizer coupling effects and the efficient utilization mechanism of young apple tree and provided a certain theoretical basis for study the water and fertilizer coupling effects of young apple tree in arid or semi-arid area. It has a certain guiding significance of young apple tree‘s planting to the fruit farmers. The main results and conclusions were as follows:(1) The two growing periods of bud flowering to new growth and fruit expansion to maturation were the most important water and fertilizer requirement period of young apple tree, and the periods of controlled water and fertilizer can effectively regulate the plant and base stem diameter growth. Comprehensive consideration, F2W2 treatment(soil moisture was controlled in 65-75% of field capacity, N-P2O5-K2 O were controlled at 20-20-10 g·tree-1) was most beneficial to the plant and base stem diameter growth, and leaf area a nd leaf area duration increase.(2) The canopy temperature of young apple tree was closely related to the water deficit condition(canopy temperature can reflect the water deficit condition),and the discrepancy between canopy and air temperature and soil moisture content have a good negative correlation. The relative water content and saturated water content of young app le trees‘ leaves showed the opposite trend and both of them can reflect the soil water deficit status. The proline(PRO) of young apple trees‘ leaves significantly increased with the water decreasing and the fertilizer increasing. Also, the content of malondialdehyde(MDA) increased with the water decreasing and had little relationship with fertilizer. Water had the leading role on SPAD values of young apple trees‘ leaves when it had not enough fertilizer, and when it had enough fertilizer, fertilizer would have the leading role on SPAD.(3) The maximum values of LWUE can‘t get by the F1W1 of high water and fertilizer treatment(soil moisture was controlled in 75-85% of field capacity, N-P2O5-K2 O were controlled at 30-30-10 g·tree-1) and it appeared at F2W2 treatment. Compared with F1W1 treatment, net photosynthetic rate(Pn), transpiration rate(Tr) and stomatal conductance(Gs) of young apple trees under F2W2 treatment decreased by 18.8%, 29.1% and 23.2% respectively, but LWUE increased by 14.2% in 2012,also decreased by 9.6%, 15.5% and 10.4% respectively, but LWUE increased by 6.5% in 2013. The effect of water on the Pn, Tr, Gs and LWUE was significantly higher than the fertilization, and Pn, Tr and Gs significantly increased by the water and fertiliza tion increasing and they all had the obvious daily change characters.(4) The average values of water consumption rate in each period(bud flowering, new growth, fruit set, fruit expansion and maturation) respectively were 4.6, 5.3, 6.2, 7.8, 4.4 mm·d-1 in 2012 and 5.6, 6.9, 8.4, 10.0, 5.3 mm·d-1 in 2013. The maximum values of CWP was on F2W2 treatment in the two years and compared with F1W1 treatment, the dry mass decreased by 5.2%, 2.3%,but water consumption decreased by 16.4%, 16.7% and CWP increased by 13.4%, 17.3% respectively in 2012 and 2013.(5) The highest yield appeared at F1W1 treatment, but there was little difference between F1W1 and F2W2 treatment. It had strong line correlation between yield and dry mass of young apple tree and the correlation index was R2=0.9085. It was beneficial to improve apple color index and reduce its shape index with increasing irrigation. Mild deficit irrigation(F2) and increased fertilizer can improve apple's vitamin C content. Irrigation was no significant effect to soluble solids content and soluble sugar content, but increased fertilizer can improve both of them. Increased Irrigation can reduce titratable acid and improve the sugar acid ratio, but fertilization was no significant effect to them.(6) The maximum values of PFP were 14.04 and 12.97 kg·kg-1 and respectively appeared at F3W1 treatment(low fertilization and well water treatment) and F3W2 treatment(low fertilization and mild deficit wa ter treatment) under the interaction effect of water and fertilizer, it showed that high irrigation and low fertilization can get the higher PFP. The maximum values of IWUE can‘t get by the F1W1 treatment, it appeared at F2W2 treatment and the yield decreased by 7.5%, but water consumption decreased by 16.7% and IWUE increased by 11.2% compared with F1W1 treatment. It had the good relationship between IWUE and CWP, IWUE and LWUE, and the CWP and LWUE both can reflect the IWUE.(7) According to the soil profile moisture migration rule in this paper, it was more beneficial to the young apple tree on the absorption of water and fertilizer under the W1(well water treatment) and W2(mild deficit water treatment) treatments, and with the increasing of water and fertilizer, it can increase the absorption of soil nitrate nitrogen and available phosphorus to the young apple tree.(8) Fertilization of 20 g·tree-1 nitrogen and 20 g·tree-1 phosphorus(the second growing season) and 20 g·tree-1 nitrogen and 10 g·tree-1 phosphorus(the third growing season) can supply the enough nitrogen and phosphorus fertilizer to young grafting apple tree. F2W2 treatment(soil moisture was controlled in 65-75% of field capacity, N-P2O5-K2 O were controlled at 20-20-10 g·tree-1) reached the best water and fertilizer coupling mode.