Effects Of Soil Acidification On Available Soil Nutrients, Soil Enzyme Activities And Characters Of Whangkeumbae In Pear Orchards

Soil pH is an important factor affecting the availability of soil nutrients that impact plant growth. We sampled and analyzed brown soils from pear orchards in thirteen towns in Wendeng county. Samples were obtained from areas along or between rows of trees at specified distances and depths. Through field investigation and laboratory analysis, the effects of soil pH value on Whangkeumbae characters and the contents of available nutrients and the correlation between mineral elements inleaves and fruits and parts of Whangkeumbae characters were preliminarily studied from October 2008 to September 2009 and evaluates the principal factors on pear growth, yield, and quality, as related to pear nutritional status. As Pyrus pyrifolia Nakai. cv. Whangkeumba is typically grown in Wendeng county, Shandong Province, this study will play a role in guiding soil improvement, balancing fertilization, and providing a resource for the synthesized management of pear orchards. The correlation between enzyme activities and soil properties were evaluated by the methods of correlation and path analysis for the September 2009 samples. The aim was to reveal the feasibility of enzyme activities used to evacuate soil fertility under soil acidification condition (1)The results showed that the soil pH fluctuated from 4.06 to 6.59 in October 2008 and from 4.24 to 7.57 in April 2009. The quantity of soil samples with pH below 5.50 increased by 34.6%. Analysis of the soil pH for samples obtained along the rows of trees showed that the pH decreased as the depth increased (except for the range 5.5 to 6.0); soil pH in the samples obtained between the rows of trees demonstrated different trends.(2)The average organic matter (O.M.) content as well as the N (NH₄⁺) and available P, Cu, Zn, Fe, and Mn contents in the samples collected in October 2008 were higher than those observed in April 2009. Conversely, the values for other available nutrients were lower than those in the samples collected in April 2009. The available nutrients and organic matter (O.M.)content in different pH ranges varied. The soil pH was significantly or very significantly correlated with N (NH4+ and NO3-), available K, Cu, Fe, and exchangeable Ca for the October 2008 samples, while a significant or very significant correlation existed between N (NH4+), available P, Zn, exchangeable Ca, and exchangeable Mg for the April 2009 samples. The correlations between soil pH and the amounts of available nutrients and organic matter (O.M.) along the rows of trees in September 2009 were nearly consistent with those between the rows.(3) The results showed that Catalase, acid phosphatase and urease were significant differences with the increase of soil depth in 4.0-4.5, 4.5-5.0, 5.0-5.5 and 5.5-6.0 regions. Meanwhile, Water Fraction by Volume and NaCl were also. The correlations of the activities of soil enzyme to soil properties were significant or very significant. Soil pH mostly significantly influenced activities of Catalase, but the direct effects of pH on invertase, acid phosphatase and urease were to a large extent counteracted by the indirect effects of other factors on them in path analysis. pH, NH4+-N, exchangeable Ca and Mg, Water Fraction by Volume and NaCl were the main factors for Catalase depending on the direct and their indirect effects. Available P, Zn and Temperature in degrees Celsius were the main impact factors on invertase. The main factors for acid phosphatase were organic matter, available P, Zn and NaCl. Organic matter, Water Fraction by Volume and NaCl were the main factors for urease. So soil enzymes were affected by pH, Temperature in degrees Celsius, Water Fraction by Volume, NaCl and soil nutrients, Catalase, acid phosphatase and urease activityes could be used as indicators of soil fertility in acidified pear orchards.(4) The effects of soil pH on soluble solids and soluble sugar, which were very significantly or significantly positive correlation, were larger than others in two tests. There were also very significantly or significantly correlation between soluble solids, soluble sugar, titratable acid of whangkeumbae and micro- or macro-elements in leaves and fruit. The contents of Fe, Mn and Cu were higher than their appropriate ranges from two tests.Their toxicities need to be payed attention to prevent. However, titratable acid content decreasing with zinc content of leaves increasing could improve fruit quality. The contents of Cu, P and Ca in fruit were also related to fruit characters. Application of lime and basic fertilizer is an effective measure to improve soil pH value, continuously fertilize and meliorate the nutrition of pear fruit.