Spatial Distribution of Soil Organic Matter and Nutrients in the Pear Orchard Under Clean and Sod Cultivation Models

The soil organic matter and nutrients are fundamental for the sustainability of pear production, but little is known about the spatial distribution of soil organic matter and nutrients in a pear orchard. With the soil of the pear （cv. Dangshansu on P.betulifolia Bunge. rootstock） orchard under clean and sod cultivation models as test materials, the experiment was conducted to evaluate spatial variability of soil organic matter （SOM）, total nitrogen （STN）, total phosphorus （STP）, total potassium （STK）, available nitrogen （SAN）, and available potassium （SAK） in and between rows at different soil depths （0-60 cm）. The SOM, STN, STP, STK, SAN and SAK of the different soil layers under the two tillage models were different in the vertical direction. The SOM, STN, STP and SAN in the 0-20 cm soil layer were higher than those in the 20-40 and 40- 60 cm soil layers. The STK of 40-60 cm soil layer was higher than that in the 0-20 and 20-40 cm soil layers. The STK increased with the depth of soil in the vertical direction in the clean cultivated pear orchard. Variability of the SOM, STN, STP, STK, SAN and SAK of sample sites in between rows of the same soil layer was found in the pear orchard soil in the horizontal direction under clean and sod cultivation management systems, except that STK of all sites did not show the difference in identical soil layers in the pear orchard under clean cultivation. The sod cultivation model improved the SOM, STN, and STK in the 0-20 cm soil layer in the pear orchard, and the three components increased by 12.8, 12.7 and 7.3% compared to clean cultivation, respectively. The results can be applicable to plan collection of orchard soil samples, assess orchard soil quality, and improve orchard soil management practices.

Performance evaluation of mechanical blossom thinning in trunk type pear orchard

In order to yield a marketable product,hand fruit thinning(HFT)has become the major but costly management practice in modern pear planting.Two kinds of new blossom thinners for pear blossom thinning were developed,which are tractor-mounted three arms blossom thinner(TTBT)and hand-held electric blossom thinner(HEBT).Four treatments for 24 trunk type‘Cuiguan’pear trees(7 years)were tested.They are TTBT combined with HFT,HEBT combined with HFT,hand blossom thinning(HBT)combined with HFT,and HFT only.Pear trees were divided into 4 groups equally.Four indexes were used to evaluate the test:flower reserve rate,fruit set rate,work efficiency and cost,fruit yield,and quality.Pear canopy was divided into the inner,middle,and outer 3 layers in the top view.20 inflorescence samples were selected for each layer.Field tests showed:there was no obvious difference in quality between mechanical blossom thinning and HBT,and the working stability of TTBT was higher than other treatments.Mechanical blossom thinning decreased the fruit set rate to a certain degree,but did not reduce the yield and quality of harvesting.TTBT could save 61.35%operation time compared with HFT,and the profitable area was 5845.76 m2.TTBT is suitable for large-scale sparse layer trunk-type pear orchards.HEBT could save 36.01%operation time compared with HFT,and the profitable area was 663.96 m2.HEBT is suitable for small and medium-sized trunk-type pear orchards.Blossom thinning can improve the average weight of high quality fruit and brix of sugar solids.

Development of unilateral obstacle-avoiding mower for Y-trellis pear orchard

To solve the problem of weeding under Y-trellis pear orchards,a unilateral obstacle-avoiding mower(UOAM)was developed in this study.The mower is composed of an obstacle-avoiding disc mechanism,a hydraulic profiling mechanism,and a cutting disc mechanism.The diameter of the obstacle-avoiding disc was 0.7 m,which could swing around the trunk or ground pile actuated by the spring mechanism.The piston movement of the hydraulic cylinder controls the working position of the obstacle-avoiding disc.The maximum extension distance of the hydraulic profiling arm was 1 m.Based on the national standards and actual situation of orchards,the optimum parameters were determined with a combination of advancing speed of 0.44 m/s,rotation speed of the cutting disc at 2000 r/min,blade number of 2,and cutting edge length of 0.2 m.Finally,the design parameters were verified by the mathematical model of the blade cutting edge trajectory and multi-body dynamics simulation.Taking stubble cutting stability,leakage rate,working efficiency and costs as the test indexes,field performance comparison tests were carried out on the three operation modes of UOAM mowing,shoulder carrying mower(SCM)mowing and manual weeding.Test results showed that the coefficient variation of stubble cutting height of UOAM was the smallest,showing that the working stability of UOAM was better than the other two treatments.The leakage rate of UOAM was 2.42%,and its coefficient variation was lower than that of SCM.The working efficiency of UOAM was much higher than that of SCM and manual weeding,which was 4.44 times of SCM and 20 times of manual weeding.The profitable area of UOAM was 7.02 hm^(2),showing that it was suitable for large-scale mechanized Y-trellis pear orchards.