磷素肥料在土壤中的變化聚積及其被旱作利用之研究

Abstract

本研究係於溫室進行，將多量磷肥（500 ppm P ）分四次同時施入本省十二種不同土壤中，每次施入後，即經浸水、風乾處理約一個月，以摸擬田間情況。四次共歷時五個月。處理過的土壤（每土壤均包括一不施磷之對照）再進行Neubauer 法磷效應試驗，種植作物為小麥。目的為探討及比較原土壤中磷素與施肥磷素之聚積型態；化學測定法有效磷值與真正有效磷值間之關係，及施肥聚積磷素之回收率。其結果摘述如下： 1. 原土壤中之磷幾乎全以Fe-P 及Ca-P 型態存在，前者在十二土壤中平均佔53.2%，後者佔44.8% ，而以Al-P 型態存在者僅佔三者總量之1.9%。在施用多量磷肥（500 ppm P ）後之土壤中Al-P 所佔的百分率升高為42.8% （十二土壤平均），Ca-P 減低為17.6%，Fe-P 減低為41.3%。又本試驗資料顯示施用磷肥500 ppm P 後土壤中的磷絕大部分（84%）以Al-P 及Fe-P 型態存在，二者之比約為1 : 1 。 2. 施肥聚積磷素之回收率（以Bray’s P-1 法測定者）在13.8%至62.2%之間，十二土壤平均為35.5% 。回收率之高低與土壤之CEC , P Sorption 及O.M. 含量成顯著負相關關係，而與有效磷含量成顯著正相關關係，如以土壤之CEC , P Sorption 及Bray’s P 三者共同估計磷素回收率，其準確性可達78% 。 3. 作物磷吸收量與土壤Bray 或Olsen 磷均有極顯著之相關關係，其相關係數依次為0.853 **及0.866 * * ；但與EUF 法測得磷之相關關係則較差。以上結果顯示以Bray 或Olsen 法測得之土壤有效磷可有效代表土壤中可被作物吸收利用之磷含量，無論此磷肥係過去或新近施用者。又本研究資料顯示作物吸收之磷在原土壤中多為Fe-P ，施肥土壤中則多為AI-P。 Phosphorus was incorporated into 12 different soils in 4 successive applications at 30 days interval in the greenhouse. After each addition, the soils were submerged for10 days, than left until dry to simulate field conditions. A total of 500 ppm P was applied while a check treatment (no P was added) was included for each soil. After this pretreatment, the soils were used for Neubauer’s P test; the plants grown were wheat. Soil chemical properties were analyzed and available P was extracted by Bray’s, Olsen’s, and EUF methods. Distribution of inorganic P fractions were determined for both the P- treated and check soils. This study was conducted to compare the distribution of inorganic P fractions in the original soil and P-enriched soil, the extractability and availability of P applied in soil as well as the P recovery rate of these soils. The results are summarized as follows. 1. P fractionation data show that in the original soil, the inorganic P forms are dominantly Fe-P (53.2%) and Ca-P (44.8%), and only 1.9% is Al-P (the average of 12 soils), whereas in the P-fertilized soil, 84% of the inorganic P fractions are Al-P and Fe-P, with a ratio of about 1: 1, and Ca-P becomes the minor part. 2. The P recovery rate (as determined by Bray’s P-l method) of the 12 soils varies greatly from 13.8 to 62.2%, with an average of 35.5%. regression study shows that P recovery rate is negatively correlated with soil CEC, P sorption, and O. M. content, but positively correlated with soil available P. When P recovery rate is estimated by soil CEC, P sorption and Bray’s P together (the multiple corrlation coefficient R=0.881**), its accuracy is 78%. 3. Quantities of soil P extracted by Bray’s, Olsen’s, and EUF methods are significantly correlated with plant P uptake, while the Bray’s and Olsen’s methods producing the higher correlation coefficients (0.858** and 0.866** respectively).This significant correlation signifies that soil available P as extracted by Bray’s or Olsen’s method can effectively represent the amount of P in soil that can be utilized by plants, no matter it is newly applied or not.