石灰質土壤聚積磷素之有效性研究

The Availability and Transformation of Phosphorus Fertilizer in Calcareous Soils of Taiwan

李子純(Tze-Shun Lee) ； 吳懷國(Hwai-Gwo Wu) ； 陳桂暖(Kuei-Nuan Chen)

《中華農業研究》 35卷3期 (1986/09) Pp. 335-349

https://doi.org/10.29951/JARC.198609.0009

摘要

本研究目的爲明瞭磷肥在石灰質土壤中之有效陸及無機磷型態的經時變化，聚積於本省石灰質土壤中磷肥的型態及其有效性，有機物對累積磷素有效性之促進效果，並探討石灰質土壤中有效磷之最佳測定方法。
採取本省中、南部代表性石灰質土壤八種，分別加入0、20及300ppm p後，置於塑膠罐中，保持田間容水量狀態，以30℃定溫孵育，定期取出測定其有效磷及無機磷型態。同時將此八種土壤，置於溫室，分別加入300ppm p（均以Ca(H2PO4)2•H2O溶解後加入）後，連同其對照，保持田間容水量狀態五個月，進行磷聚積處理，處理過的土壤在溫室進行磷肥效應盆栽試驗。盆栽試驗分對照，加磷肥20ppm p，及加泥炭0.8%三種，作物分別種植玉米及高梁，發芽後約一個月收割，記錄產量，分析其磷含量，計算磷吸收量。有效磷的測定則分別以Olsen, Bray及Modified Bray三種方法進行，結果摘要如下：
1．本試驗中所用土壤有效性磷(Olsen p)含量在9至79ppm p之間，平均爲4lppm p，含量甚高，足見本省石灰質土壤（表土）中聚積的磷肥已甚可觀。
2．在無機磷型態中，原土壤以H2SO4-P含量最高，NH4F-P次之，NaOH-P最低，各型態所佔之百分率依次爲69,19，及12%。
3．磷肥施入土壤，充分混合，經保持田間容水量狀態五個月後，仍多以NH4F-P，其次爲NaOH-P型態存在，甚少轉變爲H2SO4-P者。
4．土壤加磷後的經時變化測定顯示經加磷300ppm p六十天後，有效磷的變化即漸趨平穩，且在本省鈣質土壤巾，磷肥施用量在20~300ppm p之間時，約爲施用4ppm p，可提高土壤Olsen p 1ppm。
5.Olsen, Modified Bray及Bray三種方法測得的磷均能有效代表土壤中可被作物吸收的磷，但以前二法略優，又測值之重現性則以Modified Bray法最佳，Olsen法居次，而以Bray法最差。
6．溫室磷肥效應試驗結果顯示，土壤有效磷含量雖高，玉米、高梁仍能因施磷肥而增產，足見石灰質土壤中磷肥的重要陸，而施用0.8%的泥炭效果更超過磷肥。

並列摘要

Eight calcareous soils ranged from high to low in available P content were collected from central and southern Taiwan for this study. The changes of phosphorus availability as well as its inorganic forms were followed in the laboratory for 200 days when 0, 20, and 300ppm P were added in these soils. A P enrichment treatment was carried out in the greenhouse simultaneously. 300ppm P as monocalcium phosphate were applied in each of these eight soils and kept in field capacity for 5 months. The soils along with their check were then used in a phosphorus response experiment in the greenhouse. Corn and sorghum were planted respectively and the plants were harvested one month after emergence. Dry matter yield and P uptake were recorded. Available P was extracted by three different methods, i. e., Bray, Modified Bray, and Olsen.
The results are summarized as follows.
1. Olsen P ranged from 9 to 79 ppm P with an average of 41 ppm P in these eight soils. High available P indicated there is a high P reserve in our calcareous (surface) soils here in Taiwan.
2. The yield increase of corn and sorghum due to P application in these high P level soils revealed the importance of P fertilization in calcareous soils.
3. The inorganic P fractions of the soils before P enrichment were 69% in H2SO4-P, 19% in NH4F-P, and 12% in NaOH-P.
4. Five months after 300ppm P incorporation, the P was found mostly in the NH4F-P fraction, followed by NaOH-P, no apparent change was found in the H2SO4-P fraction.
5. Available P decreased rapidly during the first 10 days after 300ppm P addition, leveled off after 60 days. As an average, to increase Olsen P 1ppm, 4ppm P should be added in these calcareous soils.
6. High correlations were found between % yield without P, P uptake of corn, sorghum, and P extracted by the three methods used in this study, but the precision of the determination was in decreasing order with Modified Bray, Olsen, and Bray method.
7. The yield response was more prominent when 0.8% peat was applied than phosphate fertilization.