比較長期水旱田輪作或連作施用硫酸銨對於土壤酸鹼值之影響

Effect of Long-Term Application of Chemical Fertilizers on Soil pH in Different Cropping Systems

譚增偉(Tseng-Wei Tan) ； 陳桂暖(Kuei-Nuan Chen)

《台灣農業研究》 61卷4期 (2012/12) Pp. 355-360

https://doi.org/10.6156/JTAR/2012.06104.08

摘要

長期試驗田於1987年設立於本所農場，原為種甘蔗之旱田土壤，未經水田作用，屬非石灰性砂頁岩沖積土。本研究探討長期施用化學肥料下，連續20年間不同耕作制度對土壤pH的影響。不同耕作制度間造成土壤pH呈明顯差異，以水稻連作者最高、穩定且無逐年減少或增加情形，水旱田輪作者次之，旱作連作者最低並呈逐年減少趨勢，表示不同耕作制度中水田作用對穩定土壤酸鹼度的重要性。顯示施用硫酸銨氮肥之旱作連作，土壤酸化嚴重，此時pH可從水田連作之5.8下降至＜4.0，此顯示非石灰性沖積土對pH呈較低緩衝能量。水旱田輪作區，每年種玉米後pH較水田連作者在20年間平均下降1.05 ± 0.36單位，種玉米後之經一作水田則回升0.57 ± 0.29單位，但仍無法回升到原來的數值（5.8 ± 0.28）；此pH的下降幅度大而回升幅度小，應與土壤母質非石灰性、使用氮肥（NH4）2SO4及僅一作水田作用有關。

關鍵字

耕作制度 ； 連作 ； 輪作 ； 土壤酸鹼度

並列摘要

The objective of this study was to determine effect of long term application of chemical fertilizers on soil pH in different cropping systems. The long-term field experiment was conducted from 1987 to 2006 in a field of noncalcareous sandstone and slate alluvial soil at the farm of TARI. There were four treatments in this study, including rice monoculture, corn monoculture, rice-corn rotation and corn-rice rotation. The fertilizers for each rice crop were 124 kg N/ha, 140 kg P2O5/ha, and 70 kg K2O/ha, whereas the fertilizers for each corn crop were 270 kg N/ha, 140 kg P2O5/ha, and 70 kg K2O/ha. Results of the 20-year test showed that cropping systems have significant effects on pH values of soil and the maximum effect was the treatment of corn in monocropping, followed by the treatment of rice in monocropping, and the minimum effect in the treatments of rice-corn rotation and corn-rice rotation. The pH value of topsoil or subsoil was the highest in the treatment of rice monocropping, followed by the treatments of crop rotation, and the lowest in the treatment of corn monocropping. According to the relations between the pH value and the years, the pH value under rice monocropping and rice-corn rotation did not have progressively increasing or decreasing of soil pH year by year. However, the pH value of soil showed the drastic decreasing with years in the treatment of corn in monocropping. These results indicate that continuous monocropping of corn under dryland conditions and the application of high amount of ammonium-based N fertilizers for this crop are the major contributors to soil acidification. Therefore, pedogenic processes of paddy soils are important in maintaining the stability of soil pH and soil fertility in intensive agriculture.

並列關鍵字

Cropping system ； Monoculture ； Rotation ； Soil pH