Ridge Covering High-yield Cultivation Techniques of Jinhong Apple in Cold Region

Chang LIU1, Zhangli FENG1, Siyang TANG2, Haidong BU1, Minggang XIAO3, Guangjun GU1, Xianmin CHENG1, Wenquan YU1, Wanjun YE

1. Mudanjiang Branch of Heilongjiang Academy of Agricultural Sciences, Mudanjiang 157041, China; 2. Hegang Power Supply Company, State Grid Heilongjiang Electric Power Co., Ltd., Hegang 154101, China; 3. Institute of Crop Development, Heilongjiang Academy of Land Reclamation Sciences, Jiamusi 154007, China; 4. College of Horticulture, Heilongjiang Academy of Agricultural Sciences, Harbin 150086, China

Abstract After five years of study, it was found that compared with the conventional cultivation techniques, the average yield per plant of 3-5-year-old Jinhong apple trees cultivated under the ridge covering mode was increased by 2.12 times, the stem diameter was increased by 20%, the branch number was increased by 73.5%, and the underground root number was increased by 38.3%. Under the ridge covering mode, the main distribution area of the underground roots of Jinhong apple trees was moved down to 15-55 cm, the temperature of soil 20 cm beneath the surface of the ridges increased by 1.3-1.5℃, the temperature of soil 40 cm beneath the surface of the ridges rose by 0.9-1.0℃, and the water content of soil 20-40 cm from the ground was maintained around 5%. Under the ridge covering mode, the Jinhong apple trees grew robustly, began to fruit 3 years later and yielded highly 5 years later. In addition, the ridge covering model also has illumination-enhancing, pest-controlling and tillage-free characteristics.

Key words Cold region, Covering, Apple, Yield

1 Introduction

Due to thick layer of frozen soil, low temperature in early spring and slow rise of temperature in the northeast, the growth of fruit trees is often affected. Film mulching can increase soil temperature, improve crop, vegetable and fruit yield and maintain soil moisture, so as to achieve early planting and early maturity and extend harvesting period, thereby promoting early cropping and high yield of crops. This has been a well-known fact[1-4]. Fruit trees are deep-rooted perennial woody plants and they have strict requirements for nutrition, moisture and temperature of soil. Local small-scale changes in soil conditions have little effect on the growth and development of fruit trees[5]. In response to the above restrictions of the fruit trees themselves and external conditions, in the spring of 2013, a cultivation test was conducted with Jinhong apple trees by means of ridge covering.

2 Materials and methods

2.1 Overview of test siteThe test site (129°51′ E, 44°42′N) is located in the Fruit Tree Experimental Park of Heilongjiang Academy of Agricultural Sciences. The terrain is slightly low-lying. The test soil was meadow soil of dark brown soil type, with organic matter content of 11.5 g/kg and pH value of 7.76. The texture of the test soil was loamy clay. In the test site, the average temperature is 4.5℃, the absolute minimum temperature is -34.1℃, the effective accumulated temperature (≥ 10℃) is 2 500-2 700℃, the annual frost-free period is 130 d and the annual precipitation is 530-560 mm.

2.2 Test materials and methodsThe 3-year-old Jinhong apple trees of which the hard branches were top grafted withMalusbaccata(Linn.) Borkh. were selected. They were in east-west direction, at plant and row spacing of 2 m×4 m. In the spring of 2013, ridges, 30 cm×35 cm high and 140 cm wide were prepared. The mature surface soil between the rows was used for earthing up the ridges. There was only one apple tree in each plot. Total five repetitions were arranged for each treatment. The plots with representative plants were selected for conducting the test. The plots with ordinary planting were selected as a control. The area of the test site was about 1 000 m2. When the surface frozen soil (top 20-30 cm) of the ridges melted, it was covered with plastic film. The apple trees in the test plots were trimmed into the type of spindle-shaped main branch accompanied by multiple lateral branches. The application amount of organic fertilizer was 4m3/0.1 ha. In the control group, the fertilizer was applied through furrow application (60 cm deep, 80 cm wide). Before the preparation of the ridges, the surface soil was turned over and mixed with the top mature soil. The field management of fertilization and irrigation in the future was the same as the control.

2.3 Data determinationThe phenological observation and physiological indicator determination of apple trees were carried out in accordance with the "Descriptors and Data Standard for Apple (Malusspp. Mill.)"[6]. The soil moisture content (%) was determined by the drying method. That is, the soil was dried at 105-110℃ to constant weight, and the mass of lost water was measured, thus the percentage of soil moisture was calculated. Soil alkali-hydrolyzable nitrogen content was determined by alkaline hydrolysis diffusion method. Soil available phosphorus content was determined by 0.5 mol/L NaHCO3method using an ultraviolet spectrophotometer. Soil available potassium content was determined by NH4OAc extraction and measured by flame photometer[7]. The data was collated with Excel 2007 software and analyzed by SPSS software.

3 Results and analysis

3.1 Effect on vegetative growthConsidering phonological periods, no significant differences were found in germination, flowering, maturity and leaf falling between the treatment and control groups. The development of Jinhong apple trees planted under the ridge covering mode was 1-2 d earlier than the control group. There were significant differences in stem diameter and branch number between the treatment and control groups. Among them, the difference between the 2-4-year-old apple trees was extremely significant (Table 1, Table 3). The stem diameter was increased by 15.0%-29.6%, and the branch number was increased by 59%-93%.

Table 1 Effects of ridge covering and conventional cultivation on growth and development of Jinhong apple

Tree ageTreatmentStem circumference∥cmValueRatio∥%Crown diameter∥cmValueRatio∥%Plant height∥cmValueRatio∥%Branch numberValueRatio∥%Fruiting rate∥%ValueRatio∥%2-year-oldRidge covering10.5??129.610212417210387??16779.8160CK8.18216752503-year-oldRidge covering14.6??115.0188111287110364??1931000CK12.71692621891004-year-oldRidge covering16.3??120.0216110313109361??1591000CK13.6197286227100

Note:*indicates a significant difference at the 0.05 level; and**indicates a significant difference at the 0.01 level. The same below.

Table 2 Effects of ridge covering and conventional cultivation on fruit and yield of Jinhong apple

Tree ageTreatmentAverage single fruitweight∥gValueCompared toCK∥%Maximum single fruitweight∥gValueCompared toCK∥%Plant yield∥kgValueCompared toCK∥%Damaged rate(by insects)∥%ValueCompared toCK∥%3-year-oldRidge covering63147751343.15??5161.6133CK43560.614.884-year-oldRidge covering49107671317.10??7031.7228CK46511.016.135-year-oldRidge covering44986112715.70??2340.8219CK45486.704.32

Table 3 Variance analysis and difference comparison of the data about Jinhong apple under the ridge covering mode

IndicatorTree ageFF0.05F001FNew multiple range testLSR0.05LSR001LSRStem circumference∥cm2-year-old7.7121.277.850.761.252.40??5-year-old7.7121.245.13??0.791.301.90??4-year-old7.7121.2101.29??0.751.232.70??Branch number2-year-old7.7121.295.70??9.9416.4735.00??3-year-old7.7121.218 014.71??3.626.00175.00??4-year-old7.7121.2368.71??19.3932.12134.00??Plant yield∥kg3-year-old7.7121.213.10?1.923.182.50?4-year-old7.7121.293.46??1.752.906.10??5-year-old7.7121.2164.97??1.953.239.00??

3.2 Effects on yield traits of Jinhong appleThe fruiting rate of 2-year-old Jinhong apple trees in the treatment group reached 79.8%, higher than that in the control group (only 50%), with an increase of 60%. There were significant differences in the average plant yield of 3-5-year-old apple trees between the treatment and control groups. Compared with the control group, the average plant yield of Jinhong apple trees was increased by 1.34-6.03 times, the maximum single fruit weight was increased by 27%-34%, the average single fruit weight was increased by -2%-47% (becoming smaller with the aging of the trees), and the percentage of fruit damaged by insects was reduced by 67%-81% in the treatment group (Table 2, Table 3).

3.3 Effects on soil temperature and moistureFrom May 1 to June 20, 2015-2016, the soil parameters in the treatment and control groups were determined. The results showed that compared with the control group, the temperature of soil 20 cm from the ground rose by 1.3-1.5℃, and the temperature of soil 40 cm from the ground rose by 0.9-1.0℃ in the treatment group. Under the ride covering mode, the moisture of soil 20-40 cm from the ground was maintained at about 5%. The change of each indicator had a very significant linear correlation. The best perfected curves were the forth-order polynomial curve for the moisture change of soil 20-40 cm from the ground in 2015 and 2016 and the cubic polynomial curve for the temperature change of soil 20 cm from the ground in 2015 (Table 4 ).

Table 4 Effects of ridge covering and conventional cultivation on soil temperature and moisture content

Date(month-day)Treatment2015Temperature 20 cmunderground∥℃Temperature 40 cmunderground∥℃Moisture content20-40 cmunderground∥%ValueDifferenceValueDifferenceValueDifference2016Temperature 20 cmunderground∥℃Temperature 40 cmunderground∥℃Moisture content20-40 cmunderground∥%ValueDifferenceValueDifferenceValueDifference05-01Ridge covering9.71.49.30.836.30.97.11.57.11.436.81.4CK8.38.535.45.65.735.405-05Ridge covering14.01.511.90.534.72.610.61.58.60.834.22.1CK12.511.432.19.17.832.105-10Ridge covering16.11.313.20.329.60.314.01.59.80.836.4-2.2CK14.812.929.312.59.038.605-15Ridge covering17.91.416.41.129.2-0.415.11.911.41.337.2-1.5CK16.515.329.613.210.138.705-20Ridge covering20.11.717.11.028.10.717.00.815.41.335.51.2CK18.416.127.416.214.134.305-25Ridge covering22.81.018.90.727.31.619.40.516.81.134.72.6CK21.818.225.718.915.732.105-30Ridge covering21.81.319.41.726.82.222.71.519.20.631.11.7CK20.517.724.621.218.629.406-05Ridge covering20.22.118.71.228.43.321.21.518.90.833.03.3CK18.117.525.120.718.129.706-10Ridge covering19.30.718.11.826.71.121.01.218.60.433.62.4CK18.616.325.619.818.431.206-15Ridge covering20.91.717.20.729.62.222.91.319.90.733.83.0CK19.216.527.421.619.230.806-20Ridge covering19.92.117.00.830.31.720.31.218.10.934.31.9CK17.816.228.619.117.232.4Mean1.51.01.51.30.91.6

3.4 Effects on soil nutrientsOn April 14, 2015, the soil 20 and 40 cm from the ground of the treatment and control groups was sampled, and tow points were arranged for each plot. The nutrient composition of the collected soil samples was analyzed. The results showed that compare with the control group, the available nitrogen, available phosphorus, available potassium and organic matter contents of soil 20 and 40 cm from the group were improved to different extents in the treatment groups. In the top 0-20 cm, they were increased by 17.1%-22.3%, 9.5%-79.7%, 32.6%-141.9% and 8.7%-18.5%, respectively; and in the top 20-40 cm, they were increased by 18.5%-22.0%, -68.6%-14.8%, -37.2%-56.4% and 2.1%-5.9%, respectively (Table 5).

Table 5 Effects of ridge covering and conventional cultivation on soil nutrient composition

TreatmentIndicatorAvailable nitrogen∥mg/100 gValueIncrease∥%Available phosphorus∥mg/100 gValueIncrease∥%Available potassium∥mg/100 gValueIncrease∥%Organic matter∥%ValueIncrease∥%1-20 cm17.9517.17.8399.524.032.64.248.7CK16.797.16218.13.9024.7722.311.69779.730.0141.94.1718.5CK23.906.51012.43.5220-40 cm14.4218.52.94-68.612.5-37.23.922.1CK13.739.38419.93.8424.8222.02.60214.817.256.44.305.9CK23.951.64811.04.06

3.5 Effects on development of underground roots of Jinhong apple treesThe root parameters of 5-year-old Jinhong apple trees in the treatment and control groups were analyzed. The results showed that the main distribution area of apple roots under the ridge covering mode was 15-55 cm underground. Among them, the quantities of hair roots (root diameter≤0.1 cm), fine roots (0.1 cm 1.0 cm) were 565, 13 and 11, respectively. In the conventional cultivation mode, the main distribution area of apple roots was 15-35 cm underground. Among them, the quantities of hair roots (root diameter≤0.1 cm), fine roots (0.1 cm 1.0 cm) were 378, 32 and 16, respectively. Under the ridge covering mode, the distribution area of roots (15-55 cm) of apple trees significantly moved down (by 15-20 cm), there were fewer coarse roots but more hair roots and fine roots. Under the conventional cultivation mode, the roots of apple trees were distributed in the range of 15-35 cm underground, apple trees had more coarse roots but less hair roots and fine roots, and the total quantity of roots was reduced by 49% (Table 6).

Table 6 Distribution of underground roots of 6-year-old Jinhong apple trees

Treatment Maindistributionarea∥cmHair root (rootdiameter≤0.1 cm)QuantityComparedto CK∥%Fine root (0.1 cm1.0 cm)QuantityComparedto CK∥%Total root weightQuantityComparedto CK∥%Quantity of roots(rooting depth>55 cm)QuantityComparedto CK∥%Ridge covering30-5556549.513-59.511-31.358938.3566.7CK15-35378-32-16-426-3-

4 Conclusions and discussions

Compared with conventional cultivation mode, ridge covering can improve the initial fruit-bearing rate, yield and single fruit weight of fruit trees, achieving the purpose of early fruiting, early yielding and high yielding. In addition, ridge covering also has pest-repelling, illumination-enhancing and tillage-free effects.

Under the ridge covering mode, the available phosphorus, available nitrogen, available potassium and organic matter contents in the soil 20-40 cm beneath the surface were increased. This data was only measured from one-time twice re-samplings of 5-year-old Jinhong apple trees, and its reliability needs to be further verified. Ridge covering can significantly improve the yield. With the aging of apple trees, the amount and time of fertilization and irrigation should be further explored. If can be inferred from this experiment that ridge covering can also be applied to other fruit trees, especially small shrubs, berries and dwarfed trees.