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To achieve the carbonization utilization of Triarrhena lutarioriparia straw and relieve the environmental pressure caused by improper disposal in the Dongting Lake area, the agricultural efficiency of biochar derived from Triarrhena lutarioriparia was clarified. Two typical paddy soils in southern China, namely reddish clayey soil developed from a Quaternary laterite parent material and granitic sandy soil developed from a granite parent material, were selected. Six treatments with different dosage of biochar (0, 1%, 2%, 4%, 6%, and 8% of the soil mass，0-20 cm soil depth) were set. Rice pot experiments were conducted in 2020 to study the effects of different application rates of Triarrhena lutarioriparia biochar on rice nutrient utilization characteristics in two typical soils. The results showed different application rates of Triarrhena lutarioriparia biochar and soil types had certain effects on dry matter accumulation and nutrient uptake by rice organs and aboveground structures. With the addition of biochar, compared with the treatment without biochar, the accumulation of dry matter of rice increased from 0.6% to 18.6% and from 15.5% to 42.4% in the granitic sandy soil and reddish clayey soil, respectively. With the addition of 4% biochar, the accumulation of nitrogen, phosphorus, and potassium nutrients in the rice plant of the treatment increased by 8.6%, 10.5%, and 82.5% in the granitic sandy soil and by 33.8%, 100.0%, and 125.3% in the reddish clayey soil, respectively. The quadratic regression equation and fertilizer – carbon coupling model fitting showed that the optimal addition amounts of biochar in the granitic sandy soil and reddish clayey soil were 2.51% and 4.80% for nitrogen utilization, 4.33% and 7.03% for phosphorus utilization, and 4.67% and 4.81% for potassium utilization, respectively. Therefore, the application of Triarrhena lutarioriparia biochar is conducive to promoting the accumulation and growth of nitrogen, phosphorus and potassium nutrients in rice, and the amount of biochar added and soil conditions are important factors affecting the coupling effect of fertilizer and carbon. [ABSTRACT FROM AUTHOR]

【Objective】 This paper aimed to explore effects of reduced chemical fertilizer and soil texture on yield, quality and nitrogen（N）, phosphorus（P） and potassium（K） fertilizer utilization rate of flue-cured tobacco. 【Method】 Using flue-cured tobacco variety K326 as material, a field experiment was established in sandy soil, clay soil and heavy loam in Qujing tobacco production site, and six fertilization treatments were set up, i.e., T1（CK）（conventional dosage of N, P, K）, T2 and T3（deduced fertilizer N, P, K proportion by 10% and 20%, respectively）, T4 and T5（organic fertilizer replacing 10% and 20% chemical fertilizer, respectively） and T6（no manure or fertilizer）. 【Result】Compared with treatment T1（CK）, treatments T2, T3 significantly improved grade, yield, economical output and N, P, K use efficiency of tobacco leaves in sandy soil. Meanwhile, treatments T2, T3 increased contents of potassium, decreased total sugar, reducing sugar. The contents of total nitrogen, nicotine and water-soluble chloride in the middle and upper parts of leaves were not significantly affected; and the chemical composition was more balanced under T2 and T3. Compared with treatment T1（CK）, treatment T2 and T5 did not significantly improved growth of the tobacco plants in clay soil, but the proportion, yield, output and N, P, K use efficiency under T2 and T5 in tobacco leaves were significantly higher than that of T1（CK）, and the chemical composition of middle and upper position leaves was more balanced. Compared with T1（CK）, treatments T2, T3, T5 had no effect on tobacco plant growth in heavy loam, but improved the proportion of products, yield, output, N, P, K use efficiency of tobacco. Furthermore, the contents of total sugar, reducing sugar of middle and upper part leaves were increased under T2, T3 and T5. The total nitrogen, nicotine, potassium and water-soluble chloride were not affected by treatments. And treatments T2, T3 significantly improved the balance of chemical composition of tobacco leaves. Under the same N, P and K application rate, the N and P uptake and use of tobacco plants in different soils could be sorted as the following: Sandy soil>heavy loam>clay soil, and K use efficiency as the following: Heavy loam>clay soil>sandy soil. 【Conclusion】Based on the current N, P and K usage of tobacco in farmlands, the potential N, P and K proportion of chemical fertilizer reduction（CR） or replacement with organic fertilizer（ROR） in sandy soil was 10%. The N, P and K proportion of CR or ROR in clay soil was 10%-20%. The potential reduction of N, P and K fertilizer in heavy loam was 10%, and the potential proportion ROR was 10%-20%. [ABSTRACT FROM AUTHOR]

The effects of irrigation on winter wheat yield and water use efficiency (WUE) were mostly explored based on site-based experiments in North China Plain (NCP) region. However, due to the influences of contrasting environmental factors (e.g. climate and soil properties), these results cannot be accurately cross-compared among different studies, resulting in the difficulty to get the generalizable pattern at regional scale. Here meta-analysis was conducted to comprehensively evaluate the effects of irrigation on winter wheat yield and WUE in NCP region, with the observation data of 1876 pairs from 186 field experimental papers totally. The differences of the irrigation effects in different regions, precipitation year types, soil texture, and nitrogen (N) application levels were explored, and the corresponding optimal irrigation amounts for reaching high yield and WUE were ascertained. Results showed that compared with non-irrigation during the winter wheat growing period, irrigation increased the yield of winter wheat in NCP by 32.0%-38.3%, and reduced the WUE by 27.1%-30.1%. The yield increment due to irrigation in the northwest of NCP (39.6%-53.5%) with total precipitation during the winter wheat growing period below 150mm was higher than that in the southeast of NCP (24.3%-27.1%) with total precipitation during the winter wheat growing period higher than 150mm, while the decrease of WUE due to irrigation in northwest of NCP (32.4%-37.5%) was higher than that in the southeast of NCP (22.0%-24.3%). The optimum irrigation amount for high yield and WUE of winter wheat was 150-180mm in the northwest and 120-150mm in the southeast. Specifically, for different precipitation year types, the optimum irrigation amounts were 120-150mm with 2 times during jointing and flowering stages for dry year, during jointing and heading stages for normal year, and during jointing and booting stages for wet year. For different soil texture, irrigation under loamy soil had the highest increases in yield, while clay soil had the lowest decreases in WUE; the optimum irrigation amounts of winter wheat with four different soil texture of sandy soil, loam, clay loam and clay were 60-90mm, 120-150mm, 180-210mm, and 150-180mm, respectively. For different N application levels, N application of 120-240kg.ha-1 led to the highest yield and WUE under the irrigation amounts of 80-140mm, of which the higher yield was obtained under irrigation amounts of 110-140mm, and the higher WUE was obtained under the irrigation amounts of 80-110mm. Collectively, the NCP region can achieve the goals of high yield and WUE when irrigation amount was 120-150mm with 2 times but at different stages during different precipitation year types (i.e. dry year, normal year and wet year). Meanwhile, the combination of loam conditions with the N application of 120-240kg.ha-1 can synergistically improve the yield and water use efficiency of winter wheat. [ABSTRACT FROM AUTHOR]

In order to study how shear strength and its change in unsaturated soils modified by hydrophobic agent, sandy soils hydrophobized by dimethyldichlorosilane (DMDCS) were prepared. The hydrophobic soils with different DMDCS volume by soil mass, water content and clay content were obtained respectively. Mixtures of sandy soils (DMDCS volume by soil mass were 2 mL:100 g and 3 mL:100 g, i.e., 2% and 3%, the same below) with 3%, 5%, 7%, 11% and 13% water content were prepared respectively. Meanwhile, the mixtures of clay and sandy soils (3% DMDCS) according to the clay mass fraction of 0, 5%, 10%, 15%, 20%, 25%, 30%, 40% and 50% were prepared respectively. Then the unsaturated direct shear tests were carried out by unsaturated direct shear apparatus. Four samples in each group were prepared under the normal pressure in 100, 200, 300 and 400 kPa, respectively. The horizontal shearing ratio was 0.8 mm/min and the shearing test lasted 6 min. The results showed that: 1) The mixtures of sandy soils and DMDCS presented extreme hydrophobicity. 2) The water repelling of mixtures of clay and sandy soils was affected by both DMDCS and clay content. The water repelling of mixtures was degraded with the increasing of clay content, and improved with the increasing of DMDCS volume by soil mass. 3) The Mohr-Coulomb strength criterion could be adopted to describe the shear strength of hydrophobic sandy soils with different DMDCS and water content. With the increasing of DMDCS volume by soil mass, the shear strength index of the hydrophobic soil was decreased to different extents. The cohesive force showed a steep-drop shape from soil without DMDCS addition to that with 1% DMDCS and a slow decline up to stabilize finally. The effect of DMDCS on the cohesive force of modified sandy soils was much greater than on the internal friction angle. The hydrophobic soils’ cohesion with the increasing of water content was decreased gradually, while the internal friction angle was increased firstly and decreased finally. The water content had a much effect on the shear strength of the hydrophobic sandy soils. The shear strength index were decreased with the increasing of DMDCS volume by soil mass: the cohesion was declined rapidly from 19.6 kPa (no DMDCS) to 10.4 kPa (1% DMDCS) and slowly from 10.4 kPa (1% DMDCS) to 9.3 kPa (3% DMDCS). The internal friction angle was declined slowly from 16.2° (no DMDCS) to 11.8° (3% DMDCS). The cohesion was decreased with the increasing of water content: the cohesion was declined from 15.5 kPa (3% water content) to 7.5 kPa (13% water content) with 2% DMDCS and from 15 kPa (3% water content) to 5.2 kPa (13% water content) with 3% DMDCS respectively; the internal friction angle was increased from 12.7° (3% water content) to 15.2° (11% water content) with 2% DMDCS and from 11.7° (3% water content) to 14.6° (7% water content) with 3% DMDCS, then decreased to 13.9° (13% water content) with 2% DMDCS and 11.9° (13% water content) with 3% DMDCS respectively. 4) The Mohr-Coulomb strength criterion could also be adopted to describe the shear strength of hydrophobic mixed soils with different clay content. The cohesion was increased remarkably with the increasing of clay content. The cohesion of sandy soils without clay was 9.3 kPa, then suddenly increased to 27.2 kPa and 55.1 kPa mixed with 5% and 50% clay mass fraction, respectively. The internal friction angle was increased from 12.1° (5% clay mass fraction) to 16.2° (15% clay mass fraction), and then decreased to 9.7° (50% clay mass fraction). All the analysis could be beneficial to analyze the shear strength of hydrophobized soils and apply in engineering. [ABSTRACT FROM AUTHOR]