Appropriate foliar application of zinc (Zn) and zinc oxide nanoparticles (ZnO-NPs) is important for the proper growth and yield of tomato. However, the effects of foliar application of Zn and ZnO-NPs were not well-studied on tomato production. A pot experiment was conducted at glasshouse (8D) conditions under the Faculty of Agriculture, Universiti Putra Malaysia (UPM) to evaluate the effectiveness of Zn and ZnO-NPs on growth, yield, nutrient uptake, and fruit quality of tomatoes and to compare between the Zn nutrient and ZnO-NPs. Treatment combinations were 14 viz. T₁ = 0 (control), T₂ = 1500 ppm (mg/L) Zn nutrient, T₃ = 2000 ppm (mg/L) Zn nutrient, T₄ = 2500 ppm (mg/L) Zn nutrient, T₅ = 75 ppm ZnO nanoparticle, T₆ = 100 ppm ZnO nanoparticle, and T₇ = 125 ppm ZnO nanoparticle along with two tomato varieties. The experimental design was a split plot with four replications. Results indicated that foliar application of 100 ppm ZnO-NPs performed best in terms of growth parameters, physiological traits, yield attributes, yield, and quality traits of tomatoes. The same treatment (100 ppm ZnO-NPs) contributed to attain the highest nutrient uptake. Recovery use efficiency of Zn was highest with foliar application of 75 ppm ZnO-NPs. The highest yield increment (200%) over control was from foliar sprayed with 100 ppm ZnO-NPs. Comparing the two varieties, MARDI Tomato-3 (MT3) showed better than MARDI Tomato-1 (MT1). As is appears from the results, foliar application of zinc oxide nanoparticles was more efficient than conventional zinc fertilizer. Therefore, the foliar sprayed with 100 ppm ZnO-NPs can be suggested to improve quantity and quality of tomato in glasshouse soil conditions.

A pot experiment was executed to investigate the impact of biochar and compost with water-saving irrigation on the rice yield, water use efficiency, and physicochemical properties of soil. Two irrigation regimes—namely alternate wetting and drying (AWD) and continuous flooding (CF)—and four types of organic amendments (OA)—namely rice husk biochar (RHB), oil palm empty fruit bunch biochar (EFBB), compost and a control—were applied to evaluate their effects. Under the AWD irrigation regime, the maximum grain was produced by RHB (241.12 g), whereas under the same organic amendments, both AWD and CF produced a similar grain yield. Under the same organic amendment, a significantly higher water use efficiency (WUE) was observed from the AWD irrigation with RHB (6.30 g L⁻¹) and EFBB (5.80 g L⁻¹). Within the same irrigation regime, soil pH, cation exchange capacity, total carbon, total nitrogen and available phosphorus were enhanced due to the incorporation of biochar and compost, while higher soil exchangeable potassium was observed under CF irrigation for all treatments. RHB and EFBB significantly reduced the soil bulk density (up to 20.70%) and increased porosity (up to 16.70%) under both irrigation regimes. The results imply that the use of biochar with AWD irrigation could enhance the nutrient uptake and physicochemical properties of soil and allow rice to produce a greater yield with less water consumption.

Over half of the world’s population depends on rice for its calorie supply, although it consumes the highest amount of water compared to other major crops. To minimize this excess water usage, alternate wetting and drying (AWD) irrigation practice is considered as an efficient technique in which soil intermittently dried during the growing period of rice by maintaining yield compared to a flooded system. Continuous AWD may result in poor soil health caused by carbon loss, nutrient depletion, cracking, and affecting soil physical properties. Due to being a potential organic amendment, biochar has a great scope to overcome these problems by improving soil’s physicochemical properties. Biochar is a carbon enriched highly porous material and characterized by several functional groups on its large surface area and full of nutrients. However, biochar’s implication for sustaining soil physicochemical and water retention properties in the AWD irrigation systems has not been widely discussed. This paper reviews the adverse impacts of AWD irrigation on soil structure and C, N depletion; the potential of biochar to mitigate this problem and recovering soil productivity; its influence on improving soil physical properties and moisture retention; and the scope of future study. This review opined that biochar efficiently retains nutrients and supplies as a slow-release fertilizer, which may restrict preferential nutrient loss through soil cracks under AWD. It also improves soil’s physical properties, slows cracking during drying cycles, and enhances water retention by storing moisture within its internal pores. However, long-term field studies are scarce; additionally, economic evaluation is required to confirm the extent of biochar impact.

Biochar, an ecologically friendly soil amendment, is suggested for large-scale field application for its multiple potential benefits, including carbon sequestration, crop yield improvement, and the abatement of greenhouse gas emissions. However, it is unknown how effective it is in changing soil properties and its associated yield improvement when biochar is co-applied with lime in acidic soil. Here, we examined the effects of two different biochars, i.e., rice husk biochar (RHB) and oil palm empty fruit bunches biochar (EFBB), and lime on nutrient availability, the yield of maize, and soil CO₂ emission of acid soil. Biochars were applied at two different rates (10 and 15 t ha⁻¹) in combination with two rates of lime (100% and 75%), while the recommended rate of NPK fertilizers, 100% lime, and without any amendments (control) were also included. Hybrid sweet corn was grown in pots with 20 kg soils for 75 days. Plant performance and soil analyses were performed before and after crop maize cultivation while CO₂ emission was recorded. Compared to the control, combined RHB biochars with lime significantly buffered soil pH and increased nutrient availability (e.g., P by 137%), while reducing Al and Fe concentration at harvest. These changes in soil properties significantly increased maize yield (by 77.59%) and nutrient uptake compared to the control. Between the two biochars, RHB was relatively more effective in making these changes than EFBB. However, this treatment contributed to a greater carbon loss as CO₂ (209% and 145% higher with RHB and EFBB) from soil than the control. We believe that biochar-mediated buffering of soil pH is responsible for this change. Our results suggest that combined biochar application could bring desirable changes in soil properties and increase crop performance, although these effects can be short-lived.

To mitigate global climate change and simultaneously increase soil productivity, the use of biochar in agriculture can be a modern agro-technology that can help in reducing greenhouse gas emissions, enhancing soil carbon sequestration, and ultimately increasing crop yield. This study aimed to evaluate the effects of biochar and lime application on the chemical properties of acid soil and the emission of CO₂. A 60-day incubation study was conducted with eleven treatments (T) in which two different biochar produced from rice husk (RHB) and oil palm empty fruit bunches (EFBB) at two rates (10 and 15 t ha⁻¹) and on three rates of dolomitic limestone (100%, 75%, and 50%), recommended rate of NPK and a control (no amendment). The result showed that biochar and lime significantly increased soil pH, available P, and decreased exchangeable Al compared to the control. The pH increase was 44.02% compared to the control treatment on day 15, and the available P was found to be 22.44 mg kg⁻¹ on day 30 from Treatment 7 (75% lime + 15 t ha⁻¹ RHB). The cumulative CO₂ emission from T₇ was 207.40 μmol CO₂ m⁻² that decreased 139.41% compared to the control. Our findings conclude that RHB with 75% lime has more potential than EFBB to increase nutrient availability and reduce the emission of CO₂ in acid soil.

Increasing soil moisture storage capacity is a strategy that can be implemented to minimize the use of water in paddy rice cultivation. Organic materials from different sources have the potential to increase soil moisture storage and nutrient enrichment. An incubation study was conducted to evaluate the incorporation of five selected organic amendments—as follows: rice husk biochar (RHB), oil palm empty fruit bunch biochar (EFBB), compost (COMP), rice husk ash (RHA), and oil palm bunch ash (PBA), with a control (no amendment) on soil moisture storage and some chemical properties of soil. The soil was incubated with five amendments for 60 days and sampled at 15-day intervals. After completion of the incubation, a greater extent of gravimetric water content was observed from RHB (0.46 g g⁻¹) and EFBB (0.45 g g⁻¹) followed by compost (0.40 g g⁻¹). The addition of organic amendments significantly influenced soil chemical properties. Maximum soil pH was altered by PBA followed by EFBB compared to its initial value (5.01). The inclusion of EFBB finally contributed to the highest amount of total carbon (7.82%) and nitrogen (0.44%). The addition of PBA showed the highest available P and exchangeable K followed by RHB when compared with the amendments. The results indicated that RHB, EFBB, and compost retain more soil moisture compared to ash sources and added soil nutrients, indicating their potential to improve the chemical and hydrological properties of paddy soil.