Effect Of Mulching In Tree Row On Soil Physical And Chemical Features As Well As Growth And Development In Pear Trees

Mulch is an important soil management system in pear orchards and reasonablemulching is beneficial to the growth and development of fruit crops. In this experiment,5~7years old ’Whangkeumbae’ and the one year old ’Yali-pear’ were used as samplematerials, by indoor and outdoor experiments as well as field and container trials. Differenttypes of mulching materials including purple alfalfa (Medicago sativa), tall fescue(Festuca arundinacea), bluegrass(Poa annua), corn stalks(Zea mays) and white or blackplastic films were placed and the effect of mulching was studied on soil physical andchemical features as well as tree growth and development. The main results are as follows:1. Mulching in tree row can regulate the soil temperature in different months duringgrowth period. Organic materials mulch in spring and summer could decrease soiltemperature in0~20cm soil layer and this effect was significant while the corn stalks wascovered with the average monthly temperature dropping by0.50℃, compared with thecontrol. Black and white plastic film mulching during March to September showedwarming effect in each soil layer and this effect was more obvious in the surface soil. Ithad a certain effect of different mulching on daily soil temperature range and in the surfacesoil, soil temperature with white plastic film and black film mulch showed a maximumdiurnal range and clean tillage variation was larger than that with grass and corn stalksmulching. In the20~60cm soil layer, the temperature with plastic film mulching steadilymaintained at a high level and soil temperature variation with clean tillage was really large.2. The different types of mulching materials could consistently raise soilwater-holding capacity, and this effect was more significant in0~40cm soil layer. Thetransparent plastic film and black film mulching in each soil layer can effectively maintainthe soil water at a high level and the effect was particularly obvious in early spring droughtperiod. The effect of straw mulch on water-holding capacity in0~20cm soil layer wasrelatively desirable.3. Mulch could improve soil physical and chemical properties, the experiment withcontainers showed that compared with CK, the soil bulk density with straw mulchdecreased by8.82%and total porosity increased by9.09%. Straw and grass mulch could effectively increase the content of soil organic matter and the difference among them wasnot significant. Alfalfa mulch on soil could increase available nitrogen and availablephosphorus contents most significantly with an increase of28.89%and106.21%,respectively. The content of available potassium with tall fescue mulch was the highest,achieving244.96mg/kg. Tall fescue mulch on soil nutrient increases was most obvious andtotal nitrogen, phosphorus and potassium contents increased by46.03%,30.30%and7.99%,respectively. Effects of different mulches on soil enzymatic activity varied with differenttreatments: with alfalfa treatments, theinvertase activity in the soil was the highest, increasedby32.84%and with bluegrass treatment, the urease activity in the soil increased by21.97%.With tall fescue treatment, the phosphatase activity in the soil increased by56%. The effectof black and transparent plastic film mulching on soil nutrient content was not obvious.4. Mulching in tree row could improve soil nutrient conditions, and this effect wasmore obvious in0~40cm soil layer. Straw and grass mulch could effectively increase thecontent of soil organic matter, but no significant difference was found among them.Compared with the control, corn stalk mulching increased organic matter content by0.297%in0~20cm soil layer, with soil alkali-hydrolysis nitrogen, rapidly availablephosphorus and available potassium contents achieving76.09mg/kg,66.76mg/kg and256.93mg/kg， respectively. Mulching had no significant effect on increasing totalphosphorus content but total nitrogen content increased by35%. Mulching with corn stalksand tall fescue increased the total potassium content more significantly. Mulching in treerow also had a positive effect on improving the soil enzyme activity. No apparent influenceof applying black plastic film and white plastic films was found on soil nutrient contentand enzyme activity.5. Mulching with tall fescue， bluegrass and white plastic film could significantlyincrease LAI of pear trees by7.87%,6.49%and6.54%,and mulching with purple alfalfaand white plastic film could significantly improve root vitality with an increase of22.22%and24.69%,respectively. There was no marked effect of mulching on chlorophyll contentand leaf thickness but the effect was observed on leaf micro-element contents. For example,the Mn, Cu, B and Zn contents by mulching with purple alfalfa were significantly higherthan the control, being80.59mg/kg,9.62mg/kg,40.47mg/kg and24.24mg/kg,respectively.6. There was little influence of mulching on fruit firmness and soluble solid content.The titratable acid contents in fruits by covering tall fescue and black plastic filmdecreased markedly.White plastic film, tall fescue and annual bluegrass significantlyincreased average fruit weight.