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【Background and Objective】 Agriculture in many regions in China relies on irrigation, while the available water resources in some regions might not be sufficient to meet the demand. Understanding this imbalance is essential to economic management, and this paper calculates spatiotemporal variation in this balance across coastal regions in Jiangsu province. 【Method】 The analysis is based on the Gini coefficient and the Theil index using data measured from 2009 to 2020. The coupled coordination method is used to evaluate the level of coordinated development in these regions. 【Result】 The reclaimed stalinized lands in the coastal regions for agricultural production is higher than provincial average, and the balance between agricultural water resources and soil resources is lower than provincial average. The Gini coefficient characterizing the balance between agricultural water and soil resources is consistent with the Theil index, and it is ranked in the order of cultivated land benefit < agricultural water and soil resources < agricultural irrigation water benefit. The coupled coordination degree varies from 0.35 to 0.40. 【Conclusion】 The coastal regions in Jiangsu province are rich in land resources and poor in irrigation water resources. The lack of water resources is the main factor restricting development of the agricultural economy in these regions. The overall difference in the Gini coefficient and the Theil index in these regions is due to the inter-region difference; the coupled and coordinated development level in the regions is fragile and could shift from balance to unbalance.

【Objective】 Groundwater level in coastal saline-alkaline areas changes frequently due to the impact of tides. The associated water and salt movement in soil is hence more complicated than in other regions. This paper investigated the impact of groundwater depth and salinity on yield and fruit quality of tomato. 【Method】 The experiment was conducted in soil columns, with the groundwater table controlled at the depths of 90, 70, and 50 cm, respectively. Groundwater salinity was mimicked by NaCl concentration, which was controlled at 0, 2 and 4 g/L respectively. In each treatment, we measured the yield and fruit quality of the tomato. The treatments were compared using the principal component analysis and evaluation. 【Result】 The tomato yield, harvest index, average fruit weight and color index all decreased significantly with the increase in groundwater salinity, while increased significantly with the increase in groundwater depth. These four indexes were maximized when the groundwater depth was 90 cm and the NaCl concentration was zero. In contrast, vitamin C, soluble sugar, total acid and soluble solid content all increased significantly with the increase in groundwater salinity, while decreased significantly with the increase in groundwater depth. These four indicators peaked when the groundwater depth was 50 cm and NaCl concentration was 4 g/L. 【Conclusion】 Comprehensive principal component analysis shows that the comprehensive quality of the tomato increased with groundwater depth and decreased as the groundwater salinity increased. The optimal for our experiment was groundwater depth is 90 cm and the NaCl concentration is zero.

【Background and objective】 Fertilization and soil amendments are common agronomic technologies to improve soil properties and safeguard crop production, but how to optimize their applications to save fertilizers without compromising crop yield is an issue that remains largely elusive. The objective of this paper is to fill this knowledge gap. 【Method】 We took rice grown in the reclaimed coastal saline soils as an example, and simulated its growth in response to biochar and nitrogen fertilization using the ORYZA_V3 crop model. Lysimeter experiments were conducted and the experimental results were used to calibrate the model. The calibrated model was then used to evaluate the impact of different nitrogen fertilizations and biochar amendments on crop growth and yield. 【Result】 The ORYZA_V3 model was capable of simulating the growth and yield of rice grown in the saline soils. When nitrogen application was low, amending the soil with biochar can increase the rice yield at significant level. However, the improvement depends on nitrogen application rate. When nitrogen application was more than 235 kg/hm2, nitrogen did not appear to be a limiting factor for the crop and the efficacy of amending the soil with biochar for improving crop growth and yield was also waning. For example, when the nitrogen fertilization was 235 kg/hm2, adding 2% of biochar (w/w) gave a yield 8 680.1 kg/hm2, while when the nitrogen fertilization was 141 kg/hm2, add 5% of biochar could increase the rice yield to 8 834.1 kg/hm2. Amending the saline soil with biochar is hence an effective way to reduce nitrogen application without compromising crop yield. 【Conclusion】 The efficacy of amending the reclaimed coastal saline soils with biochar to improve rice yield was when nitrogen fertilization application was low, and its efficacy waned as the nitrogen application increased. These results have important implications for rice production in regions with salt-affected soils.

【Objective and objective】 Soil aggregate is a function unit commonly used to describe the impact of soil structure on soil fertility and quality. It is temporally dynamic, modulated by a myriad of biotic and abiotic factors such as wetting-drying cycles and root-induced activity. One method to characterize aggregate fraction is fractal dimension. This paper is to study the relationship between fractal dimension of aggregates and physical and chemical properties of coastal soil. 【Method】 Intact soil samples were taken from natural uncultivated land and rice fields at the Tiaozini reclamation area in Dongtai city, Jiangsu province. The fractions of water-stable aggregates in each sample were determined using wet-sieving, and fractal dimension of the soil aggregates under different cultivations was calculated by box-counting method. To elucidate the genesis of soil aggregation, we analyzed the correlation between fractal dimension and physical and chemical properties of the soils. 【Result】 Compared with the natural uncultivated land, planting rice increased soil macroaggregates by 4.21% and reduced fractal dimension of its aggregates by 0.03. Fractal dimension of the aggregates was negatively correlated with fraction of large aggregates, and negatively correlated with fraction of small aggregates. The mean weight and geometric diameters of the aggregates were negatively correlated with the fractal dimension. Factor analysis and correlation analysis both showed that the contents of Na+, Mg2+, Ca2+, K+, SAR and Cl- in the soil were positively correlated with the fractal dimension at significant level. 【Conclusion】 Planting rice increased the fraction of large aggregates and reduced fractal dimension of the aggregates of coastal soil, thereby improving soil structure. Fractal dimension of the aggregates was affected by contents of Na+, Mg2+, Ca2+, K+, SAR and Cl- in the soil at significant level.

To minimize the number of soil water content (SWC) measurements for estimation of field- or watershed-scale soil water storage, we present an analysis of time-stable soil water data across both measurement locations and soil depth intervals. The proposed analysis applies the time stability concept to select area-representative measurement locations, and assesses the potential for identifying the most time-stable depth interval (MTSD) using a minimal number of selected time-stable locations (MTSLs). For that purpose, we used a time series of 21 SWC datasets, measured at 20 locations and 20 corresponding depth intervals down a 3-m soil profile, during a two-year period in the 38-ha study area of the Liudaogou watershed of the China Loess Plateau. After identifying the MTSLs, analysis of time stability of measurement depth intervals showed single soil water depth measurements at between 2 and 5 of the MTSLs were sufficient to determine the area-representative SWC. The MTSD was determined to be about mid-way in the soil profile, irrespective of total soil profile depth measured. Confirmation of the time-stability analyses was done by comparing the representative SWC estimations for the 38-ha sampling area with additional SWC measurements across the 6.9km2 watershed. The encouraging results of our analysis suggest that time stability analysis may be an effective way to assess large-scale soil water storage in arid and semi-arid regions.

To effectively control nonpoint source pollution and predict its transport and load, understanding water and solute transport processes, patterns and mechanisms is essential. However, the measurement of water movement and solute transport parameters is usually a laborious and time‐consuming task. It is important to predict water movement and solute transport parameters from more readily available soil physical and chemical properties. In this study, a database of soil hydraulic and solute transport parameters containing information retrieved from 83 published studies on soil properties, land use, management measures, etc. was established to characterize and simulate soil water movement and solute transport processes. Our results showed that the soil particle composition was closely related to all soil hydraulic and solute transport parameters. As the soil texture changed from sand to clay, the soil residual water content (θr) obviously increased. The soil porosity was significantly positively correlated with θr, saturated water content (θs), van Genuchten parameter α, dispersity (λ) and retardation factor (R) and negatively correlated with van Genuchten parameter n (p < 0.01). The use of random forest models allowed the prediction of soil hydraulic and solute transport parameters by inputting common or even incomplete soil property parameters. The bulk density and particle composition jointly contributed 66% to the prediction of the soil hydraulic parameters and 44% to the prediction of the solute transport parameters. The pH exerted a notable impact on the solute transport parameters, especially dispersion coefficient (D), λ and R. The results may be useful in providing data support and facilitating the development of watershed nonpoint source pollution models. [ABSTRACT FROM AUTHOR]

Soil salinity is a severe worldwide environmental problem that adversely affects soil properties and the crop growth such as okra. We hypothesized that biochar soil amendments could increase the okra salt threshold, alleviate salt stress and improve soil productivity. In this study, a pot experiment was conducted to investigate whether biochar could ameliorate the effects of salinity on okra plants. Three biochar amendment (BA) soil applications (0%, 5% and 10% by mass of soil) were considered for seven irrigation water salinity levels (0.75, 1.0, 2.0, 4.0, 5.0, 6.0 and 7.0 dS m−1) in a randomized block design with three replications. The Maas and Hoffman salt tolerance model was used to evaluate the effects of BA on okra plant growth parameters (e.g. yield, biomass) and water use efficiency for each salinity treatment. The results showed that increasing the soil salinity levels caused significant decreases in plant yields and yield components. However, biochar application rates of 5% and 10% increased the okra threshold by 19.7% and 81.2%, respectively, compared to the control (0%). The 10% biochar application rate also resulted in the greatest okra plant growth and increased yield, indicating that the effects of salt stress were ameliorated; moreover, the soil bulk density was decreased, and the water content was increased. Hence, biochar soil amendments could be considered as an important agronomic practice that could potentially overcome the adverse effects of salt stress.