Effects of the age of raised beds on the physicochemical characteristics of fruit orchard soil in the Vietnamese Mekong Delta

Abstract

To grow fruit plants, farmers in the Vietnamese Mekong Delta (VMD) must use raised bed constructions to avoid waterlogging during the rainy season. This study aimed to evaluate the effects of the age of the raised beds on the soil physicochemical properties of longan orchards located in the VMD. Two raised bed systems were evaluated: a young bed constructed 10 years ago and an old bed constructed 42 years ago. Soil samples were collected from five different soil layers (0–20, 20–40, 40–60, 60–80, and 80–100 cm) with four replicates per layer. Soil samples were tested for pH, electrical conductivity (EC), available phosphorus (AP), total nitrogen (TN), soil organic matter (SOM), exchangeable cations (Ca2+, K+, Mg2+, and Na+), cation exchange capacity (CEC), bulk density (BD), soil porosity, available water-holding capacity (AWC), particle composition (sand, silt, and clay), and size. The soil pH was approximately 1.0 units lower in the old bed compared to the young bed at depths of 0–20 and 20–40 cm. The BD was higher in the old bed (0.15 g cm−3) than in the young bed at a soil depth of 0.4 m. SOM, AP, exchangeable cations (Ca2+, Na+, and Mg2+), AWC, and soil porosity were significantly lower in both the topsoil (0–20 cm) and subsoil (20–40 cm) layers in the old bed than in the young bed. In particular, the SOM, AP, AWC, and soil porosity contents in the old bed decreased by 18%, 20%, 15%, and 17%, respectively, compared with those in the young bed at soil depths of 0–40 cm. Therefore, cultivating raised bed soil for a longer period significantly reduced the soil exchangeable cations, porosity, and fertility of the surface and subsurface soils. Based on these results, farmers should use soil conservation practices, such as cover crops, rice straw mulching, and soil amendments in their orchards to mitigate topsoil degradation.

Use of the Diagnosis and Recommendation Integrated System (DRIS) for Determining the Nutritional Balance of Durian Cultivated in the Vietnamese Mekong Delta

“…Moreover, most durian trees are cultivated in raised beds in which the surface soil is always higher by 0.5 m compared with the water in the canal. This reduces the exchangeable cations because these cations runoff due to rainfall and irrigation [26]. Although growers applied a certain amount of P for their gardens, P is a limited nutrient in durian leaf.…”

“…Although growers applied a certain amount of P for their gardens, P is a limited nutrient in durian leaf. P use efficiency decreased due to P being precipitated by Al and Fe under low pH conditions, resulting in increasing insoluble hydroxide compounds that are unavailable for plant uptake [26]. Therefore, soil pH regulation is necessary for improving the availability of P in soil.…”

“…These locations occupy the largest area of durian cultivation, which is considered to have high potential for durian production in the VMD region [25]. The average annual precipitation and air temperature in the period 2020-2022 were 1818 mm and 27.6 • C, respectively [26]. Our previous studies [26,27] indicated that soils are classified as alluvial soils, with high fertility at the soil depth of 0-20 cm, rich soil organic matter (25-30 g kg −1 ) and total N content (1.0-1.5 g kg −1 ), and optimal soil bulk density (~1.0 g cm −3 ); data were shown on a dry weight soil.…”

“…The average annual precipitation and air temperature in the period 2020-2022 were 1818 mm and 27.6 • C, respectively [26]. Our previous studies [26,27] indicated that soils are classified as alluvial soils, with high fertility at the soil depth of 0-20 cm, rich soil organic matter (25-30 g kg −1 ) and total N content (1.0-1.5 g kg −1 ), and optimal soil bulk density (~1.0 g cm −3 ); data were shown on a dry weight soil. The pH value of soils was 4.5-5.0, which was extracted in distilled water with a ratio of soil/distilled water (1:2.5).…”