『Abstract
The main goal of agricultural management practices in irrigated
agroecosystems in the Brazilian semi-arid is either to maintain
or increase soil quality. In these areas, the reduction in soil
quality is mainly associated with depletion of soil organic matter
(SOM), as well as of soil phosphorus (P) reserves. We aimed to
evaluate changes in SOM and P fractions of a eutrophic haplic
cambisol (Eutric Cambisol) under different uses and management
systems in the irrigated perimeter of Jaguaribe/Apodi in Ceara(後のaの頭に´) State, Brazil. The evaluated irrigated
agroecosystems were perennial banana (Musa ssp.) cultivation
(IPBC) and annual maize (Zea mays L.) cultivation (IAMC).
The respective natural vegetation (NVIB) and (NVIM) were selected
and used as a reference. Soil samples were collected at 0-5, 5-15,
15-25, and 25-40 cm soil depths, and evaluated for total organic
carbon (TOC), total nitrogen (TN), humic substances, fractions
of oxidizable organic carbon, and organic and inorganic P fractions.
The stocks of TOC, TN, and humic substances in topsoil have been
reduced by cultivation, and the largest reductions were observed
in the IAMC area. The degree of SOM oxidation decreased with soil
depth and the greatest amounts of labile C were found in IAMC.
Annual and perennial agroecosystems showed changes in reserves
of soil P. Our results pointed out that irrigated agroecosystems
in the Brazilian semi-arid regions need to adopt management practices
that favor the building up of soil SOM contents, particularly
where annual crops are cultivated.
Keywords: Soil management; Irrigated cultivation; Soil organic
matter; Soil phosphorus』
1. Introduction
2. Materials and methods
2.1. Study area
2.2. Soil sampling and analytical procedures
2.3. Statistical analysis
3. Results and discussion
3.1. Total soil C and N
3.2. Changes in soil humic substances
3.3. The carbon management index
3.4. Phosphorus fractions
4. Conclusions
Acknowledgements
References
※リンの抽出分別法は、Bowman(1989)による酸(硫酸)−塩基(水酸化ナトリウム)法を用いている。