Potassium Mobilization and Transformation in Red Paddy Soil as Affected by Rice

Abstract

A rhizobox experiment was conducted to study the effect of growing rice (Oryza sativa L.) on the movement and transformation of K in a red paddy soil. Results showed that K uptake by rice reduced the concentrations of soil water‐soluble K (Sol‐K), exchangeable K (Ex‐K), and non‐exchangeable K (Nonex‐K) in the root zone. Soil Sol‐K in non‐root‐zone compartment close to the root zone (0–6 cm) migrated toward the root zone, and soil Ex‐K (0–4 cm) and soil Nonex‐K (0–3 cm) was released into soil solution. As the rice growth progressed, soil Sol‐K, Ex‐K, and Nonex‐K in the root zone and soil Sol‐K in non‐root‐zone compartment close to the root zone (0–6 cm) continued to decrease. Decreases of soil Ex‐K and Nonex‐K in non‐root‐zone compartment extended from the root to 6 and 5 cm into the bulk soil, respectively. At the late grain‐filling stage, soil Sol‐K concentration in the root zone and non‐root‐zone compartment (0–6 cm) declined, and then remained stable, whereas Sol‐K in the non‐root zone (6–7 cm) kept diffusing toward the root zone. Soil Ex‐K and Nonex‐K in the root zone and non‐root‐zone compartment continued to reduce, and the decrease distance of soil Nonex‐K was extended to 6 cm. Within the whole season, soil Ex‐K and Nonex‐K were the main forms of K available to the plants, followed by Sol‐K. The information obtained in this study indicated that K fertilizer should be added to the place around the root zone.

Effects of rice (Oryza sativaL.) cultivation and soil type on potassium mobilization and transformation behavior

“…The root zone had the largest decreases in the different forms of K in both YCS and FS with rice growth, which was consistent with the results in red soil (Li et al 2014). In addition, the deficits of different forms of K were greater closer to the root zone.…”

“…In our study, the migration distances of Sol-K in YCS and FS were studied in detailed at all stages of rice growth, and the results showed that the migration distances differed greatly at the early stage of rice growth, being 6 and 5 cm at the maximum tillering stage and 7 and 6 cm at the panicle initiation stage, whereas at the late grain-filling stage, the migration distances of Sol-K were 7 and 7 cm, showing little difference between YCS and FS. The study by Li et al (2014) showed that the migration distances of Sol-K in red soil was 6 cm at all stages. It showed that soil type had an impact on the migration distance of K, which may be related to the content of soil texture and clay composition.…”

“…A rhizobox experiment (Jungk and Claassen 1997;Kitsopoulos 1999;Li et al 2014) was carried out in a potted site from May to September in 2012. In the rhizobox, a 60 mm thick center was fixed as the root-zone compartment, which was separated with 30 μm aperture nylon mesh (Li et al 2014). Plants were sown in this compartment.…”

“…Previous studies have shown that the distance of K migration was 6-11 cm in red soil and 4.0-7.5 cm in fluvo-aquic soil (FS), and it moved faster in the early stages of crop growth (Du and Zhou 2005;Du et al 2009). A study on the migration distance of different forms of K in red soil (Li et al 2014) showed that the soil formed a K + concentration gradient from the root zone to the nonroot zone, with the root zone having the lowest K + concentration and the migration distances of Sol-K was 6 cm, the depletion of Ex-K and Nonex-K was 6, 4, and 3 cm, respectively. Diffusion occurs when the soil solution has a concentration gradient, and it is affected by soil texture, moisture, temperature, and so on (Horst 1981;Barber 1985).…”

“…The soil had a greater migration resistance with finer soil particles, higher clay content, and thicker water membrane (Zhan et al 2012). Previous studies have focused on the chemical behavior of K in one specific type of soil (Du and Zhou 2005;Du et al 2009;Li et al 2014), but there are few studies on the migration and transformation of K in different soil types under the same environmental conditions. In our study, a rhizobox trial was carried out in which the soil was divided into the root zone and the nonroot zone.…”