Electrolytes have been verified as a vital internal factor controlling soil aggregate stability (SAS). Several reports have focused on whether potassium promotes or demotes SAS and have shown contradictory results in different soils and clay mineralogy. Only a few studies have investigated such an effect on a soil-plant system, even though this information is critical for soil management practices to maintain soil structural stability. This research studied the dynamics of SAS as influenced by potassium in a soil-plant system. Corn as a test plant was grown on Haplic Acrisols (Typic Paleustults) in a greenhouse. The potassium adsorption ratio (PAR), cation ratio of structural stability (CROSS), and SAS were recorded on the day before planting (day 0), the day of planting (day 1), days 10, 20, 30, and the day of harvesting (day 55) at the tasseling stage. The corn growth, biomass, and potassium uptake were also examined. The relationship between soil and plant parameters was statistically tested. The results showed the existence of SAS dynamics caused by soil potassium change, with agreement among the responses for PAR, CROSS, and plant uptake. Within 24 h of soil treatment with potassium, the SAS move rapidly from 74% to 96%. It remained steady at 96–97% when the corn was in the vegetative stage and then fell significantly (α = 0.05) to 88% when the corn was in the tasseling stage, where the potassium uptake was maximized. The results implied that SAS is a sensitive index of soil physical quality associated with potassium, especially for tropical kaolinitic soils.

This study evaluated the effects of diatomite (DT) and fly ash (FA) on soil pH, silicon (Si) availability, nutrient partitioning, and sweet corn (Zea mays L. var. saccharata) productivity in sandy loam soil under greenhouse conditions in northeastern Thailand. A 12-week pot experiment was conducted using a completely randomized design with DT (6 and 12 g/pot), DT combined with FA (10 and 20% of DT), silicic acid (SA), and a control. Combined DT + FA treatments increased soil pH by up to 17.8% (6.57 to 7.74) and enhanced water-soluble Si by up to 53.6% (51.35 mg/kg), indicating sustained Si release. Sweet corn yield was improved, with the highest cob fresh and dry weights recorded under DT (12 g/pot) + FA (10%) (~30% increase over control). The highest total fresh biomass was observed under DT (6 g/pot) + FA (10%), suggesting enhanced vegetative growth at lower DT rates. Nutrient uptake increased markedly, particularly for N and Si, with Si accumulation mainly seen in straw. These responses reflect integrated effects of Si availability, pH improvement, and nutrient inputs rather than Si alone. Overall, DT + FA improved soil properties and plant performance; however, results from this short-term pot study should be interpreted cautiously. Long-term field studies are required to assess sustainability and environmental risks.

When cultivating medicinal plants, the use of chemical substances such as pesticides and chemical fertilizers should be avoided, as these can be contaminated with hazardous substances. Bio-fertilizers are a good alternative for growing herbs, as they are produced from organic materials that contain fewer hazardous substances. The aim of this study was to investigate the effects of different bio-fertilizers on growth, yield, andrographolide content, nutrient accumulation, and different pigments in green chiretta. In addition, the effectiveness of bio-fertilizers on the convertible phosphorus content in the soil was investigated. The experimental design was a completely randomized design (CRD) with four treatments and four replicates. The details of the experiment were 1) control (no bio-fertilizer), 2) phosphate-solubilizing microorganisms (PSMs), 3) plant growth promoter, and 4) mycorrhiza. The findings revealed that the application of PSMs provided the highest leaf dry weight (yield) of green chiretta (20.8±3.58 g/plant). This treatment also gave the highest chlorophyll a, b and total chlorophyll content (699±70, 178±24, 880±94 mg/sqm, respectively) and andrographolide yield (0.38±0.06 g/plant). Regarding the phosphorus content in the soil, the PSMs application showed the highest available phosphorus and the highest phosphorus activation coefficient (PAC) in the soil, namely 52.0±4.76 mg/kg and 4.22±0.32 percent, respectively. These results indicate that the use of PSMs as a bio-fertilizer is most suitable for the cultivation of green chiretta, especially when this plant grows on acid sulfate soils.

Long‐term phosphorus (P) limitation in tropical agroecosystems requires organic amendments and P fertilizer, with better insights needed into how soil organic carbon (OC) regulates P behavior under continuous fertilization. A field trial in loamy sand soil in Northeast Thailand was established in 2018 to assess the 5‐year effects of chicken manure (CM) and P fertilizer on yield and agronomic performance of cassava, soil P pools, OC distribution across particle fractions, and its mineralization during 63 days of incubation. Four treatments were compared: control (no CM or P), sole application of P or CM, and combined application of P and CM. The results in this study were obtained from the 2022 growing season, with soil samples collected after cassava harvest. Sole CM significantly increased cassava tuber yield by 66.7% over the control. Combined CM + P treatment did not increase tuber yield over sole but produced significantly higher aboveground biomass than sole P treatment and the control. This corresponded to the significantly highest P use efficiency parameters and uptake in cassava that received the sole CM. Soil P was predominantly in the Po pool, which showed limited variation among fertilization treatments. Notably, the sole CM significantly increased all Pi fractions, particularly soluble Pi. The cumulative C–CO ₂ mineralization and OC contents in different fractions varied significantly across treatments, with the highest one observed in sole CM. In the incubation study, a decrease in the POM‐like C fraction and an increase in the MAOM‐like C fraction were observed. These raised P levels in most Pi pools, significantly increasing soluble and occluded Al–/Fe–Pi in CM‐applied treatments. The findings highlighted that the applied P rate, CM, and CM + P prevented soil P depletion by increasing particle‐associated OC and plant‐available P in the Pi pool, thereby enhancing cassava agronomic performance from both agronomic and environmental perspectives.

Long‐term integrated fertilization can improve crop productivity and soil fertility in tropical sandy soils; however, nutrient‐specific responses of cassava productivity and soil N dynamics remain poorly understood. This study evaluated the effects of nitrogen (N), phosphorus (P), and potassium (K) fertilization under a 5‐year chicken manure (CM)‐based system on cassava yield, nutrient uptake, nutrient use efficiency (NUE), soil properties, and N mineralization. Three independent split‐plot field trials (CM–N, CM–P, and CM–K) were established in 2018, with cassava yield and soil parameters assessed during the fifth cropping cycle (2022/2023 growing season). In each trial, the focal nutrient was excluded from the blanket fertilization and applied at three treatment rates, while the other two nutrients were uniformly supplied. Integrated application of CM and chemical fertilizers significantly increased cassava yield and plant nutrient uptake, while responses of NUE indices varied among the independently conducted N, P, and K trials. CM combined with the highest N and P rates increased fresh tuber yield by 40.4% and 40.8% in the CM–N and CM–P trials, respectively; in the CM–K trial, CM with or without K increased yield by 59.1%–81.0%. CM also increased soil organic carbon (SOC) and nutrient availability, although responses in water‐stable aggregates (WSAs) were inconsistent. Under laboratory incubation conditions, N mineralization showed limited responses to P fertilization in the CM–P trial. In the CM–N and CM–K trials, CM combined with the respective mineral fertilizers was associated with changes in the potentially mineralizable N pool and mineral N release kinetics. Importantly, increases in the potentially mineralizable N pool were not necessarily accompanied by increases in the mineralization rate constant, indicating treatment‐dependent mineralization kinetics. Overall, the findings demonstrate nutrient‐specific responses to integrated CM and mineral fertilization and indicate that mineral nutrient requirements should be considered individually when developing CM‐based fertilizer management for cassava on low‐fertility sandy soils.