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Abstract Greenhouse gases can cause acid rain, which in turn degrades soil chemical properties. This research was conducted to determine the effects of simulated acid rain (SAR) on the chemical properties of Nyalau series (Typic paleudults). A 45-day laboratory leaching and incubation study (control conditions) was conducted following standard procedures include preparing simulated acid rain with specific pH levels, followed by experimental design/plan and systematically analyzing both soil and leachate for chemical changes over the 45-day period. Six treatments five of which were SAR (pH 3.5, 4.0, 4.5, 5.0, and 5.5) and one control referred to as natural rainwater (pH 6.0) were evaluated. From the study, the SAR had significant effects on the chemical properties of the soil and its leachate. The pH of 3.5 of SAR treatments decreased soil pH, K+, and fertility index. In contrast, the contents of Mg2+, Na+, SO4 2−, NO3 −, and acidity were higher at the lower SAR pH. Furthermore, K+ and Mg2+ in the leachate significantly increased with increasing acidity of the SAR. The changes in Ca2+ and NH4 + between the soil and its leachate were positively correlated (r = 0.84 and 0.86), whereas the changes in NO3 − negatively correlated (r = − 0.82). The novelty of these results lies in the discovery of significant alterations in soil chemistry due to simulated acid rain (SAR), particularly impacting soil fertility and nutrient availability, with notable positive and negative correlations among specific ions where prolonged exposure to acid rain could negatively affect the moderately tolerant to acidic and nutrient-poor soils. Acid rain can negatively affect soil fertility and the general soils ecosystem functions. Long-term field studies are required to consolidate the findings of this present study in order to reveal the sustained impact of SAR on tropical forest ecosystems, particularly concerning soil health, plant tolerance, and potential shifts in biodiversity and ecological balance.

The ecosystem's biodiversity and soil microorganisms are impacted by the increasing use of synthetic fertilizers and pesticides, which causes soil acidity and limits the sustainability of agricultural output. The majority of microbial functions in acidic soil are inhibited because of decreasing nutrient cycling and organic matter decomposition as well as diminishing bacterial and fungal growth and reproduction. In light of these growing concerns, the use of microorganisms as bio fertilizers is a recommended as alternative agricultural practice. Recent times have brought about a change in the paucity of study on yeasts and their ability to safely boost plant growth. Numerous works on bacteria have been made available. The primary objective of the study is to highlight the widespread application of yeasts in sustainable agricultural practices to promote plant growth in acidic soils. All of the advantages that yeasts provide may contribute to the growth of plants. Therefore, a thorough investigation into yeasts may be fruitful and offer a sustainable means of boosting agricultural yields that are necessary in acidic soil.

The amendment of soils with silicate (Si) compounds is essential to promote growth performance and control Fusarium wilt disease in bananas. Two successive greenhouse trials were conducted at the experimental farm of the University of Putra Malaysia. The treatments were arranged in split plots using a randomized complete block design (RCBD) with four replicates to investigate the effects of Si compounds and application frequency on controlling FOC. Si compounds were used at a constant concentration of 0.1%: T0 (control), T1 (13% SiO2:20% K2O), T2 (26.6% SiO2:13.4% K2O) and T3 (36.2% SiO2:17% Na2O). There were three application frequencies by day intervals (DI): 0DI (without any application), 7DI (12× within 12 weeks after transplanting (WAT)), 15DI (6× within 12 WAT) and 30DI (3× within 12 WAT). From these findings, we observed that the photosynthesis rate started to increase from 10.6 to 19.4 µmol CO2 m−2s−1, when the total chlorophyll content started to increase from 3.85 to 7.61 mgcm−2. The transpiration rate started to increase from a value of 1.94 to 4.31 mmol H2O m−2s−1, when the stomata conductance started to increase from 0.237 to 0.958 mmol m−2s−1. The proline content started to increase from 22.89 to 55.07 µmg−1, when the relative water content started to increase from 42.92 to 83.57%.

Foliar fertilization is a reliable technique for correcting a nutrient deficiency in plants caused by inadequate nutrient supply to the roots in acid soil. Soluble nutrients in banana pseudostem sap might be effective to supplement chemical fertilizers. However, the limited nutrients in sole banana pseudostem sap as foliar fertilization may not meet-up the nutritional demand of the crop. Field trials were, therefore, conducted with the combination of soil-applied fertilizers with foliar spray of banana pseudostem sap to increase nutrient uptake, yield, and quality of sweet corn planted in acidic soil. Three treatments viz., 100% recommended dose of fertilizers (RD) as control (T1), 75% of RD applied in soil with foliar application of non-enriched banana pseudostem sap (T2), and 50% RD applied in soil with foliar spray of enriched banana pseudostem sap (T3) were replicated four times. The combination of soil-applied fertilizer with foliar spray of enriched banana pseudostem sap (T3) showed a significant increase in leaf area index (11.3%), photosynthesis (12%), fresh cob yield (39%), and biomass of corn (29%) over control. Besides, the 50% RD of soil fertilization with foliar spray of enriched pseudostem sap increased nutrient uptake in addition to an increase in sugar content, phenolic content, soluble protein, and amino acids of corn. Considering the economic analysis, the highest net income, BCR (3.74) and MBCR (1.25) values confirmed the economic viability of T3 treatment over the T1. The results suggest that foliar spray of enriched banana pseudostem sap can be used as a supplementary source of nutrients to enhance nutrient uptake by corn while increasing yield and minimizing chemical fertilizer use in acid soil.

Biostimulants such as silicate (SiO32−) compounds and antagonistic bacteria can alter soil microbial communities and enhance plant resistance to the pathogens and Fusarium oxysporum f. sp. cubense (FOC), the causal agent of Fusarium wilt disease in bananas. A study was conducted to investigate the biostimulating effects of SiO32− compounds and antagonistic bacteria on plant growth and resistance of the banana to Fusarium wilt disease. Two separate experiments with a similar experimental setup were conducted at the University of Putra Malaysia (UPM), Selangor. Both experiments were arranged in a split-plot randomized complete block design (RCBD) with four replicates. SiO32− compounds were prepared at a constant concentration of 1%. Potassium silicate (K2SiO3) was applied on soil uninoculated with FOC, and sodium silicate (Na2SiO3) was applied to FOC-contaminated soil before integrating with antagonistic bacteria; without Bacillus spp. ((0B)—control), Bacillus subtilis (BS), and Bacillus thuringiensis (BT). Four levels of application volume of SiO32− compounds [0, 20, 40, 60 mL) were used. Results showed that the integration of SiO32− compounds with BS (108 CFU mL−1) enhanced the physiological growth performance of bananas. Soil application of 28.86 mL of K2SiO3 with BS enhanced the height of the pseudo-stem by 27.91 cm. Application of Na2SiO3 and BS significantly reduced the Fusarium wilt incidence in bananas by 56.25%. However, it was recommended that infected roots of bananas should be treated with 17.36 mL of Na2SiO3 with BS to stimulate better growth performance.

Azolla pinnata is a small floating fern which widely occurs in certain regions such as Southeast Asia. Azolla is utilized in the new plant research on the currently existing products for soilless growth media. Soilless growth media are an alternative component to replace soil for cultivation uses. In urbanization scenario nowadays, most of the flatten open-area soil is used for development, affecting the soil supply for plants. To introduce a new component such as the soilless growth media, it must have the same or more nutrients than soil or other existing soilless growth media. A study found that Azolla is used as a soilless growth media in the nursery for olive trees cultivation. According to the study, the nutrients obtained from Azolla are sufficient to replace soil as a growth media. In this experiment, the Single Dry Ashing, and Kjeldahl and Dummas methods were used to evaluate and compare both macro and micronutrients of Azolla to Midorie Pafcal and Jiffy-7 pallets. Based on the results, the values were 0.94 % (N), 4352.00 ppm (P), and 563.13 ppm (K); compared to 1.35% (N), 377.13 ppm (P), 1512.33 ppm (K); and 0% (N), 563.13 ppm (P), 1343.67 ppm (K), respectively. The results also showed the values of Copper (Cu), Iron (Fe), and Zinc (Zn) for Azolla, Midorie Pafcal and Jiffy-7 samples were 15.33 ppm (Cu), 2579.67 ppm (Fe), 93.63 ppm (Zn); 7.53 ppm (Cu), 9988.33 ppm (Fe), 26.77 ppm (Zn); and 13.01 ppm (Cu), 1150.30 (Fe), 12.40 ppm (Zn), respectively. In conclusion, Azolla pinnata is capable of providing the nutrients required for a plant, making it suitable as a soilless growth media for all plants.

The conversion of chicken feathers, generated annually worldwide on a large scale as a by-product of the poultry industry into value-added products, has economic and environmental benefits. Protein hydrolysate produced from feathers has attracted significant attention in agriculture as a potential plant growth stimulant. Therefore, a study was established with the aim to produce and characterize chicken feather protein hydrolysate (CFPH) and investigate the effects of this product on the early growth of nursery tea plants. Alkaline hydrolysis was used to produce CFPH with the yield of 165 mg amino acids per gram of feathers. Then, the produced CFPH was applied on nursery tea plants as a soil drench at different doses (0.5, 1, 2, 3, and 4 g L−1) in 2-week intervals until the 10th application. Commercially available fish protein hydrolysate (FPH) was included as a treatment to compare the effects with CFPH. The treatments were arranged in a completely randomized block design with three replications. CFPH and FPH significantly improved the shoot and root growth parameters. Plant height (+98%), leaf number (+61%), shoot dry biomass (+128%), root length (+94%), root surface area (+15%), and root dry biomass (+152%) were significantly increased by the application of CFPH (2 g L−1 dose) compared to control. Although the highest CFPH dosage (4 g L−1) showed a reduction in growth parameters, the values obtained were similar or higher than the untreated control plants. The chlorophyll content (a, b, and total) was enhanced by the CFPH dosage of 1 g L−1, whereas the highest photosynthetic rate was recorded in the CFPH 3 g L−1 treatment. The application of protein hydrolysates (PH) did not positively influence stomatal conductance and intercellular CO2 concentration. Leaf nitrogen, phosphorous, manganese, and copper were positively affected by the CFPH application. The effect of CFPH on growth parameters was more pronounced than FPH. Our findings reveal that CFPH produced by alkaline hydrolysis could be used as a growth booster in raising vigorous tea nursery plants, which are most suitable for field planting and subsequently higher yields.

Acid soil is an obstacle to agricultural development and a concern regarding food and environmental security. Therefore, a study was carried out for two consecutive years to see how lime and organic manure (OM) amendments affect yield and nutrient absorption in the Transplanted (T.) Aman–Mustard–Boro cropping pattern in an acidic terrace soil. With nine treatments and three replications, the experiment was set in a randomized complete block design. The treatments were applied to the first crop, T. Aman, with different dosages of lime (dololime at the rate of 1 and 2 t ha−1), OM (cow dung at 5 t ha−1, poultry manure at 3 t ha−1) and lime–OM combination, and their residual effects were studied in the following mustard and boro rice crops. Results demonstrate that the effect of lime and manure was more pronounced in the case of the second and third crops in the first year and of all crops in the pattern in the second year. In the first year, grain and straw yield of T. Aman as well as the overall system productivity were not influenced significantly by the application of lime and manure, but significant increases were obtained in the second year. As an average of both years, the highest grain yield of 5.2 t ha−1 (12% over control) was recorded for T. Aman, 1.7 t ha−1 (41% over control) for mustard and 5.9 t ha−1 (47% over control, 3.9 t ha−1) for boro rice when dololime was applied in combination with poultry manure. In both years, N, P, K and S uptake were significantly increased compared to the control in all the crops due to the combined application of lime and cow dung or poultry manure. Combined application of lime and manure amendment significantly improved nutrient availability and soil quality. Therefore, applying lime in combination with manure can be practiced to uplift crop productivity in acidic terrace soils.

Biochar can be a good soil amendment to reduce the soil pH, increase crop growth rate, and improve the efficient use of fertilizer. Other than that, silicon fertilizer also would promote photosynthetic ability on plant development that would help to produce high yield. In this work, a series of experiments was conducted to observe the effect of rice husk biochar and silicon fertilizer on the maize growth rate and soil pH. A 45-day pot experiment in the greenhouse with three replicates of 9 experimental treatment combinations of RHB at two rates (5 and 2.5 t.ha-1) with silicon fertilizer at three rates (125%, 100%, 75%), sole biochar (10 t.ha-1), sole silicon fertilizer (100%) and control (NPK) to observe the best rate and combination to improve growth rate and change in soil chemical in acid soil. The result showed that the co-application of sole biochar and biochar with Silicon significantly improved growth development, increased photosynthesis rate, altered soil pH, and reduced Fe concentration compared to control. The plant height increased 88.35% from T4 (5 t.ha-1 RHB + 100% Si) compared to the control and the conductance was higher in T4 (0.53) followed by T8 (0.438) while T1 (0.071) recorded the lowest conductance. The shoot fresh weight was higher in T4 (127.83 g) followed by T8 (57.14 g). However, the weight increased by 343.7% at T4 followed by T8 (2.5 t.ha-1 RHB + 75% Si) at 98.33%. The highest pH increment of 1.24 units (T1 = 5.53, T4 = 6.77) of soil pH was noted from T4 (5 t.ha-1 RHB + 100% Si) compared to control (NPK), and the highest total Fe in soil was observed from T1 (442.30 mg.kg-1). The current study results showed that T4 (50% RHB + 100% Silicon) was the best treatment over the other rates of RHB and silicon increased plant height, photosynthetic rate, and biomass.