Richard Bell

Context
Dry season irrigated rice has the potential to increase food production and cropping intensity in the salt-affected coastal areas of the Ganges Delta, but its success is often limited by seasonal salinity, scarcity of freshwater and elevated temperatures. We hypothesized that earlier transplanting would overcome these constraints and maximize productivity.

Objective
The objective of this study was to evaluate how transplanting times interact with salinity and temperature and affect rice yield and water productivity in a saline ecosystem.

Methods
Field experiments were conducted at Dacope, in the Khulna district of Bangladesh, during 2023–24 and 2024–25 seasons with a single salt-tolerant rice cultivar and six transplanting dates (15 and 30 December, 15 and 30 January, 14 and 28 February) in a randomized complete block design. Soil salinity (EC1:5), solute potential, crop growth parameters and water productivity were measured along with yield and its components at harvest.

Results
Seasonal rainfall, temperature, and salinity strongly influenced crop performance. Transplanting on 15 and 30 December was associated with higher leaf area, biomass, tillers m−2, grain panicle−1, thousand grain weight and grain yield (7.0–7.2 t ha−1 in 2023–24 and 7.4–7.6 t ha−1 in 2024–25). Irrigation water salinity was higher in 2023–24 (2.5–6.2 dS m−1) than in 2024–25 (1.9–4.0 dS m−1), largely due to lower rainfall in the first season. Delayed transplanting after 30 December decreased yield by 11–64 % in 2023–24 and 11–54 % in 2024–25. Higher yields on 15 and 30 December were associated with lower soil salinity, higher soil solute potential, and lower daily maximum temperature during the maximum vegetative and reproductive stages. In contrast, late planting after 30 December exposed crops to more days exceeding 33 0C during reproductive stage, along with higher salinity and lower solute potential during reproductive and ripening stages, which led to high levels of panicle sterility. Transplanting on 30 December also resulted in the highest irrigation water productivity (0.86–0.91 kg m−3) and total water (irrigation and rainfall) productivity (0.84–0.86 kg m−3), while crop water productivity based on evapotranspiration was the highest with 15 December transplanting (2.51–2.62 kg m−3).

Implications
Transplanting Boro rice by 30 December enables crops to escape high soil salinity and elevated temperature during reproductive growth, thereby improving both grain yield and water productivity in the salt-affected coastal areas of the Ganges Delta. Adopting this practice can help farmers intensify their cropping systems by integrating high yielding salt-tolerant dry season irrigated rice with monsoon-season rice production.

Context. Plant available silicon (Si) levels in soils are of increasing interest due to the growing evidence that Si enhances plant tolerance to a range of stresses. Aim. On a diverse range of agricultural soils of Western Australia (WA), the aim was to determine the relationship between the Si concentrations in CaCl2 or acetic acid extracts and soil properties and predict the prevalence of Si deficiency. Methods. To assess the Si status in soils of WA, 203 geographically-dispersed soil samples were collected from the WA wheatbelt (spanning from Geraldton to Esperance) with a range of physicochemical characteristics in 2023 and 2024. Comprehensive soil analysis (CS) including organic carbon, pHCaCl2 ,pHH2O, texture, electrical conductivity, extractable phosphorus and potassium, DTPA-extractable micronutrients (copper, zinc, manganese and iron), exchangeable calcium, magnesium, sodium and potassium, and effective cation exchange capacity (ECEC) plus Si extraction by CaCl2 and dilute acetic acid was completed. Key results. The mean ECEC, pHCaCl2 and organic carbon were 5.85 ± 0.59 cmol kg−1,5.65 ± 0.60 and 0.68 ± 0.48%, respectively. Based on a tentative Si critical range (20–40 mg kg−1), 74.9% of samples were under 20 mg kg−1 while 88.2% were below 40 mg kg−1 (in CaCl2). For soils with SiCaCl2 < 20 mg kg−1, statistical means for SiCaCl2 ,pHCaCl2 and ECEC were 8.70 ± 0.35 mg kg−1, 5.45 ± 0.06 and 4.00 ± 0.36 cmol kg−1, respectively. Conclusion. Based on matching our results with the mean for pH, ECEC and exchangeable cations for WA soil types, 4.62 million hectares is predicted to be low in SiCaCl2 , while another 6.3 million hectares is predicted to be marginal. Implications. We recommend a priority set of experiments for assessing the impact of Si in WA wheatbelt soils on mitigation of drought and salinity.

Context
Low organic matter and clay content in sands result in poor water and nutrient retention, which limit the crop and pasture productivity on such soils throughout the world. Compost amendments to sands can increase the reactive surface area and improve nutrient and water holding capacity. However, the added nutrients in composts can be leached rapidly in sandy soils especially when they decompose quickly.

Aims
It is hypothesised that clay addition with compost could increase nutrient retention and reduce the nutrients leached in sands.

Methods
A leaching experiment was conducted in columns to investigate the effect of compost and clay amendments on water and nutrient retention under two different irrigation/rainfall regimes at two fertiliser rates.

Results
Compost addition at both 10 and 30 t/ha had positive effects on initial water retention in sand. Clay added at 6% under high irrigation conditions also significantly increased initial water retention compared to unamended sand. The clay and compost combinations reduced ammonium and phosphorus leaching by 30% and 30–50%, respectively, compared to unamended sands. The addition of clay at 6% with compost 30 t/ha reduced potassium leaching by 25% compared to compost only.

Conclusions
Compost at 30 t/ha ± clay retained significantly higher levels of phosphorus, potassium, sulfur, calcium, magnesium, zinc, boron and manganese than unamended sand and clay-only treatments in final soils under both irrigation and fertiliser rates.

Implications
Combined compost and clay amendments, compared to single applications of either compost or clay-only, improved water retention which could potentially support plant growth in sands during dry periods, and retention of nutrients that otherwise are prone to leaching on sands.

R. Bowichean, R. W. Bell, M. Cheng, S. Thanachit, and S. Anusontpornperm, “Release Kinetics of Boron in Acidic Soils as Affected by Calcium Form Different Sources,” Applied and Environmental Soil Science 2024 (2024): 6418954, https://doi.org/10.1155/aess/6418954.

The article was originally published incorrectly as a Review article. The correct article type is ‘Research Article’, and the article has been updated to reflect this.

We apologize for this error.

Water-saving irrigation is essential for crops in saline regions where freshwater resources are scarce. We tested furrow irrigation methods and planting techniques in terms of yield, water savings, water productivity (WP), soil salinity (ECe) and soil water content (SWC) for sunflower in saline soils. Planting on the top of the ridge (T) or side slope on the ridge (S) were tested in factorial combination with (i) skip fixed furrow irrigation (SFFI), (ii) alternate furrow irrigation (AFI) or (iii) every furrow irrigation (EFI). The sunflower yield was significantly greater with the side of the ridge planting than on the top of the ridge. In consecutive years, sunflower yields were not significantly different among the furrow irrigation combinations with planting on side slopes of ridges. However, compared with the EFI, the SFFI and AFI saved 25%- 28% of the irrigation water and improved the WP. At a soil depth of 30 cm, the SFFI and AFI had significantly lower ECe values than did the EFI. Both skip furrow methods, with side slope planting on the ridge, offer water savings without sacrificing yields while decreasing the soil salinity and increasing the WP of sunflower in the water-scarce, saline coastal regions of the Ganges Delta.

Chickpea has become an increasingly popular healthy food worldwide. Aluminum (Al) toxicity is a major hurdle for chickpea cultivation and yield improvement in acidic soils. However, the genetic mechanism of Al-tolerance in chickpea remains poorly understood. Here, we performed a large-scale hydroponics screening and SNP chip array genotyping of 1154 diverse chickpea accessions. Root lengths after 6 days cultivation under hydroponics in control (T0: pH 4.2) and Al treatment (T1: pH4.2, 15/20 μM Al3+) were measured. Root tolerance index (RTI = T1/T0) ranking revealed significant variations in chickpea Al-tolerance, with common Australian chickpea cultivars positioned in the low to medium range. Genome-wide association analyses revealed eight QTLs on chromosomes ca1 (CaAlt1-1), ca3 (CaAlt3-1), ca4 (CaAlt4-1, CaAlt4-2), ca5(CaAlt5-1), ca6 (CaAlt6-1), and ca7 (CaAlt7-1, CaAlt7-2) associated with T1, implying a multigenic genetic basis for Al-tolerance in chickpea. Specifically, CaAlt7-2 was associated with both T1 and RTI, whilst CaAlt4-2 was detected for T1 uniquely in the HatTrick x CudiB22C population. Al- tolerant and sensitive haplotypes for the identified QTLs were also identified. Organic acid transporter genes CaMATE2, CaMATE4, and CaALMT1 were found in proximal genomic regions to CaAlt7-2, CaAlt4-1, and CaAlt6-1, respectively. Further qRT-PCR in parental chickpea lines (HatTrick, Slasher, Gunas, CudiB) confirmed that CaMATE2 and CaMATE4 were strongly induced upon Al treatment. Interestingly, CaMATE2 was preferentially expressed in the upper part of the root, whilst CaMATE4 preferentially in the root tips, implying a potential complementary role in Al resistance. Their direct roles in Al tolerance and the potential alternative candidate genes near the QTLs require further investigation. This first report of QTLs on Al-tolerance in chickpea has substantially advanced our understanding of the genetic basis of Al tolerance in chickpea and will facilitate the rapid breeding of Al-tolerant chickpea cultivars for previously un-accessible acidic soils.

Understanding soil potassium (K) availability is critical for developing K fertilizer recommendations, especially in regions with low soil K reserves. The quantity/intensity isotherm and K release were used to evaluate the dynamics of K in loam-and clay-textured soil types developed from highly weathered parent materials in Western Australia (WA). Twenty-one soil types with a wide range of properties were collected from 0–10, 10–20 and 20–30 cm depths on farmland in WA. The equilibrium activity ratio of K+ varied from 0.1 × 10-3 to 45.6 × 10-3 (mol L-1)1/2 and was significantly higher in surface soils than subsurface soils. The labile K (KL) ranged from 0.03 to 2.18 cmolc kg−1, and the contributions of non-specifically adsorbed K towards KL were >50 % in surface soils but lesser in subsoils. The potential buffering capacity (PBCK) ranged from 5.4 to 185 cmolc kg−1 (mol L-1)-1/2 and was significantly correlated with soil effective cation exchange capacity (ECEC), pH and clay content. The ECEC alone explained 94.5 % of the variation in PBCK. The cumulative amounts of K released after 213 h ranged from 27 to 833 mg kg−1, with a rapid release of K up to 22 h followed by a gradual release until the end. In conclusion, most soils, especially surface soils, had adequate K availability for crop production but it is vulnerable to losses and depletion. Given the overall low ECEC and PBCK, split or delayed K applications are recommended, alongside practices that enhance K buffering capacity in WA soils.

Aims
Production of high yielding forage grasses on the extensive areas of tropical sandy soils in the Lower Mekong Basin is constrained by acidity, low soil nutrient concentrations, and potassium and sulfur depletion, limiting the ability of rural households in the region to meet the economic opportunities arising from the growing demand for livestock products in Asia. This research aimed to measure the response of forages grown in sandy soils that were provided with additional potassium sulfur, and lime inputs. It was hypothesized that additional potassium, sulfur and lime above local recommendations would increase biomass production and soil organic carbon concentrations.

Methods
An experiment was conducted over two years in the Lao PDR to compare the response and soil organic carbon accumulation of forage grasses grown in sandy soils that were either managed according to recommended fertilizer and manure additions, or provided with additional potassium and sulfur at four different rates, and lime.

Results
Yield increases of 25% were achieved with additional K and S but benefits were conditional on season and variety. Soil organic carbon concentration in the top 5 cm increased by up to 1.38 t ha−1 with forage production.

Conclusions
High yielding forages are likely to become limited by soil potassium. The imbalance of supplied nitrogen relative to potassium highlights inefficiencies in the recommended rates relative to forage production requirements, demonstrating potential to improve productivity and reduce nitrogenous waste. Increases in organic carbon stocks indicate the potential for improved forages to provide environment benefits.

Context: Silicon (Si) is a beneficial element which can improve plant tolerance to abiotic and biotic stresses, while also improving nutrient uptake. Aim: The aim was to determine the extent of Si depletion and the crops most responsible by developing a partial Si balance for Australian cropland. Methods: A literature review was performed to assess Si content in Australian cropland soils and, based on records from the Australian Bureau of Agricultural and Resource Economics and Science, annual Si removal from the soils due to uptake by the main crops was estimated. Australian results were compared to global Si removal estimates for the 15 most harvested crops recorded by the FAO. Key results: The estimate of Si removal rate for cropland in Australia in 2020, from 66.6 million tonnes (Mt) annual production on 31 million ha, was 3.8 Mt, equivalent to 122.6 kg ha−1. Based on two scenarios (I – annual replenishment of plant-available Si in soils; II – same as Scenario I plus significant Si leaching from soils), there are negative Si balances in Australian agriculture. The seven top Si accumulator crops account for 77% of Si removal in Australian croplands. Conclusion: The negative Si balance in Australian croplands is lower than for other parts of the world (−35 to −87 vs −83 to −137 kg ha−1 year−1) but these values may be underestimates, pending determination of Si leaching rates in Australian croplands. Implications: The implications of soil Si depletion warrant further examination considering the numerous stresses encountered by the crops grown in Australia.

Context
Agricultural productivity in the coastal saline zones of the Ganges Delta in Bangladesh and West Bengal, India faces significant constraints due to high soil salinity, seasonal waterlogging, freshwater scarcity, and increasing climatic variability. These challenges collectively limit the sustainability and intensification of dry season (Rabi) cropping systems, thereby impeding regional food security and livelihoods.

Objective
This study aimed to assess the key biophysical constraints affecting Rabi season cropping systems and to evaluate the integration of key agronomic and water management technologies using a combination of field experimentation and cropping systems modelling, with the goal of supporting climate-resilient intensification in coastal saline environments.

Method
Two years of field experimentation were conducted across multiple locations, generating a comprehensive validation dataset comprising 139 crop instances, including transplanted Aman (T. Aman) rice, wheat, maize, sunflower, grass pea, and lentil. These datasets represented a diverse range of potentially integratable technologies and agroecological conditions. The Agricultural Production Systems Simulator (APSIM), employing the APSIM-SWIM3 module, was used to simulate crop production outcomes for a range of different integrated technologies. To achieve this, a novel modelling approach was developed to dynamically simulate surface soil salinity and moisture, and then its subsequent effects on crop production, using daily inputs of water table depth, salinity, irrigation, and climatic data.

Results and conclusions
APSIM simulations closely matched observed field data, with performance metrics (RMSE, R2) falling within acceptable ranges of experimental uncertainty. Long-term (25-years) scenario analyses demonstrated that advancing sowing dates by 15–30 days could substantially increase yield potential by reducing salinity exposure during critical crop stages. However, early sowing increased the risk of waterlogging, especially in low-lying fields. In some cases, the incorporation of in-field drainage structures was shown to mitigate waterlogging risks effectively. In situations where this is not possible due to landscape constraints, model-based identification of optimal sowing periods provided a viable alternative to reduce risk of waterlogging. Additionally, the retention of crop residues was shown to reduce surface soil evaporation and salinity accumulation, increasing yield, particularly in late-sown Rabi crops.

Significance
Focusing on the integration of four key technologies— short-season improved Kharif rice varieties, early Rabi crop sowing, field drainage, and crop residue retention—this study delivers a validated, model-supported decision framework for enhancing Rabi cropping in coastal agroecosystems. The results offer a scalable foundation for site-specific agronomic planning, community-based water management, and policy formulation aimed at climate-resilient cropping system intensification in the vulnerable coastal saline regions of South Asia.