Long‐term biochar application promotes rice productivity by regulating root dynamic development and reducing nitrogen leaching

Biochar is beneficial for improving soil quality and crop productivity. However, the long‐term effects of biochar addition on temporal dynamics of plant shoot and root growth, and the changes in soil properties and nitrogen (N) leaching are still obscure. Here, based on a long‐term (7 years) biochar field experiment with rice in northwest China, we investigated the effects of two biochar rates (0 and 9 t ha^?1 year^?1) and two N fertilizer rates (0 and 300 kg N ha^?1 year^?1) on shoot and root growth, root morphology, N leaching, and soil physicochemical properties. The results showed that both biochar and N fertilizer significantly promoted rice growth, with their interaction significant only in some cases. Both fertilizers enhanced rice shoot biomass and N accumulation in various growth stages as well as increased grain yield. Nitrogen fertilizer significantly promoted root growth regardless of biochar application. However, biochar application without N fertilizer increased root biomass and length during the whole growth period, except in the booting stage; biochar with N application promoted root growth at tillering, reduced root biomass but maintained root length with low root diameter and high specific root length during the jointing and booting stages, and then delayed root senescence in the grain filling stage. Long‐term applications of biochar and N fertilizer reduced 10%–12% bulk density of topsoil compared to the control treatment with no N fertilizer and no biochar. Long‐term biochar application also improved soil total organic carbon and concentrations of available N, phosphorus, and potassium. In addition, biochar and N fertilizer applied together significantly reduced nitrate and ammonium concentration in leachate at different soil depths. In conclusion, biochar could regulate root growth, root morphology, soil properties, and N leaching to increase rice N fertilizer‐use efficiency.     

Nutrient levels within leaves,stems, and roots of the xeric species Reaumuria soongorica in relation to geographical,climatic, and soil conditions

Besides water relations, nutrient allocation, and stoichiometric traits are fundamental feature of shrubs. Knowledge concerning the nutrient stoichiometry of xerophytes is essential to predicting the biogeochemical cycling in desert ecosystems as well as to understanding the homoeostasis and variability of nutrient traits in desert plants. Here, we focused on the temperate desert species Reaumuria soongorica and collected samples from plant organs and soil over 28 different locations that covered a wide distributional gradient of this species. Carbon (C), nitrogen (N), and phosphorus (P) concentrations and their stoichiometry were determined and subsequently compared with geographic, climatic, and edaphic factors. The mean leaf C, N, and P concentrations and C/N, C/P, and N/P ratios were 371.6 mg g⁻¹, 10.6 mg g⁻¹, 0.73 mg g⁻¹, and 59.7, 837.9, 15.7, respectively. Stem and root C concentrations were higher than leaf C, while leaf N was higher than stem and root N. Phosphorus concentration and N/P did not differ among plant organs. Significant differences were found between root C/N and leaf C/N as well as between root C/P and leaf C/P. Leaf nutrient traits respond to geographic and climatic factors, while nutrient concentrations of stems and roots are mostly affected by soil P and pH. We show that stoichiometric patterns in different plant organs had different responses to environmental variables. Studies of species-specific nutrient stoichiometry can help clarify plant–environment relationships and nutrient cycling patterns in desert ecosystems.     

Effects of biochar and nitrogen addition on nutrient and Cd uptake of Cichorium intybus grown in acidic soil

Biochar is an organic amendment used for soil remediation, there are only a few studies documenting the effects of nitrogen on the role of biochar in contaminated soils. A pot experiment was conducted to investigate the impacts of biochar (0%, 1%, and 2.5%, w/w) and nitrogen (0, 100, and 200 mg N kg^?1) on plant growth, nutrient and cadmium (Cd) uptake of Cichorium intybus. N, P, Ca, Mg, and Cd concentrations increased with N level in 0% and 1% biochar treatments. In plants treated with 2.5% biochar, 200 mg N kg^?1 addition caused significant reductions of N, P, Ca, Mg, and Cd concentrations in comparison to 100 mg N kg^?1 treatments. Nitrogen promoted shoot biomass at all biochar treatments, while biochar had no effect on shoot biomass in 0 and 200 mg N kg^?1 addition treatments. Nitrogen also significantly increased N, P, K, Ca, Mg, and Cd contents in the 0% and 1.5% biochar addition treatments. Although soil DTPA-extractable Cd concentration showed the lowest values in 1% biochar in combination with 100 and 200 mg N kg^?1 addition treatments, lowest shoot Cd concentration, and relatively high shoot biomass occurred in the 2.5% biochar + 200 mg N kg^?1 treatment. Based on these results, biochar application at its highest rate (2.5%) in combination with high N supply (200 mg N kg^?1) contributed to both crop yield and agricultural product safety. N input alone might increase the risk of human health, and the optimum N dose should be determined during phytostabilization process.     

Effect of substituting nitrogen fertilizer with nitrogen-fixing cyanobacteria on yield in a double-rice cropping system in southern China

The efficient use of nitrogen fertilizer to increase rice production is essential for food security in China. However, the high-input of chemical nitrogen fertilizer has also resulted in soil N losses and environmental pollution. Here we investigated the possibility of using biofertilizer to reduce nitrogen fertilizer use via partial substitution of chemical nitrogen fertilizer (NF) with nitrogen-fixing cyanobacteria (NFC) in red soil. The effects of 100% NF (N10C0) and different substitution rates of NF with NFC (70%, 50%, 30%, and 0% NF plus 30%, 50%, 70%, and 100% N obtained through NFC, labeled as N7C3, N5C5, N3C7, and N0C10, respectively) on rice yield and soil properties were assessed in a double-rice system in greenhouse (six treatments) and field experiments (four treatments) from 2018 to 2019. The N10C0 and N7C3 treatments had no significant effect on grain and straw yields and the nutrient uptake in the greenhouse experiment. The higher substitution treatments could not sustain stable rice yields and the nutrient uptake in either greenhouse or field experiments, which indicated that 30% substitution was appropriate to sustain rice yields. For rice growth traits, higher substitution rates (70–100%) significantly decreased the number of tillers/plant and panicles/plant. In general, soil TN and TP contents in the 0–15 cm layer increased with increasing substitution rate during the early and late rice seasons. Compared to the N7C3 and N5C5 treatments, there were no significant differences in NH₄⁺-N and NO₃^?-N contents under the N10C0 treatment. Compared to the application of NF as the sole nitrogen source, 30% substitution with NFC could result in monetary savings of approximately 5.77 US$ ha^?1. Taken together, our findings demonstrate that substituting NF with an appropriate amount of NFC is beneficial for improving the productivity and sustainability of paddy fields under the double-rice cropping system.

     

Influences of rice straw biochar and organic manure on forage soybean nutrient and Cd uptake

Abstract

This pot experiment aimed to investigate the influence of rice straw biochar (BC 0, 1, and 3%, w/w) and organic manure (OM 0, 1, and 2%, w/w) addition on the growth, nutrient and cadmium (Cd) uptake of forage soybean in 10 mg Cd kg^?1 contaminated soils. Compared with non-biochar treatments, biochar decreased shoot biomass, height and nitrogen (N) contents. Organic manure markedly increased the shoot biomass, shoot phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) concentration, and root N, P, Ca contents without biochar addition treatments, while in the case of 3% biochar, there were no significant effects on N, K, Ca, and Mg contents of shoot and root among organic manure treatments. In comparison with other treatments, the minimum Cd content of shoots and roots both occurred in the treatment of BC3%+OM2%, while shoot Cd content reached the maximum value in OM2% treatment. Thus, these results suggested that organic manure addition can elevate forage soybean yield and nutrient content, while biochar had no positive effects. High biochar (3%) addition in combination with highest dose of organic manure (2%) can decline the Cd content of soybean and contribute to the agricultural product safety.     

Biochar Application Enhanced Post-Heading Radiation Use Efficiency in Field-Grown Rice (<i>Oryza sativa</i> L.)

It has been shown that adding biochar to soil can improve nitrogen (N) uptake and utilization in rice (Oryza sativa L.). However, there is a lack of research on the physiological alterations of rice as a result of the changes in nitrogen uptake due to the addition of biochar. This study conducted field experiments in 2015 and 2016 with the goal of testing the hypothesis that the application of biochar would enhance radiation use efficiency (RUE) of rice by improving the plant’s ability to take in and utilize nitrogen. Our results demonstrated that the application of biochar (20 t ha⁻¹ ) induced no significant effects on pre-heading specific leaf weight (SLW), nitrogen uptake (NUpre), and leaf area index (LAI) at heading, the ratios of LAI/NUpre and SLW/Nupre, or pre-heading RUE. However, biochar application significantly increased post-heading nitrogen uptake (NUpost), ratios of NUpost/SLW and NUpost/LAI, and post-heading RUE. These results indicate that the application of biochar can improve the plant’s nitrogen uptake and RUE in field-grown rice during the post-heading period, which con- firms our hypothesis.     

Influence of Biochar on Nitrogen Use Efficiency and Root Morphology of Rice-Seedling in Two Contrasting Paddy Soils

Biochar may affect the root morphology and nitrogen (N) use efficiency (NUE) of rice at seedling stage, which has not been clearly verified until now. To clarify it, we conducted a pot experiment regarding to two soil types (Hydragric Anthrosol and Haplic Acrisol), two biochar application rates (0.5 wt% and 1.5 wt %) and two rice varieties (common rice var. Xiushui134 and hybrid super rice var. Zhongkejiayou12-6) meanwhile. Seedling NUE of common rice Xiuhui134 was significantly increased (p < 0.05) by 78.2% in Hydragric Anthrosol and by 91.4% in Haplic Acrisol following biochar addition with 1.5 wt%. However, biochar addition exerted no influence on seedling NUE of super rice Zhongkejiayou12-6 in both soils. Overall, 0.09–0.10 units higher soil pH and 105– 116% higher soil NH₄⁺ -N were observed in Xiushui134 growing two soils with 1.5 wt% biochar. In addition, improved root morphology (including longer root length, larger root surface area, bigger root volume, and more root tips) contributed to the higher seedling NUE of Xiushui134 in two soils. The soil pH and NH₄⁺ -N content, also the root morphology were influenced by biochar, which though could not thoroughly explained the NUE of Zhongkejiayou12-6. In conclusion, biochar application to paddy soil changed soil pH and NH₄⁺ -N content, root growth, and the consequent seedling NUE of rice, which effects are relative with rice cultivar, biochar addition rate, and soil type.     

Successive straw biochar application as a strategy to sequester carbon and improve fertility: A pot experiment with two rice/wheat rotations in paddy soil

Aims

A pot study spanning four consecutive crop seasons was conducted to compare the effects of successive rice straw biochar/rice straw amendments on C sequestration and soil fertility in rice/wheat rotated paddy soil.

Methods

We adopted 4.5 t ha^?1, 9.0 t ha^?1 biochar and 3.75 t ha^?1 straw for each crop season with an identical dose of NPK fertilizers.

Results

We found no major losses of biochar-C over the 2-year experimental period. Obvious reductions in CH₄ emission were observed from rice seasons under the biochar application, despite the fact that the biochar brought more C into the soil than the straw. N₂O emissions with biochar were similar to the controls without additives over the 2-year experimental period. Biochar application had positive effects on crop growth, along with positive effects on nutrient (N, P, K, Ca and Mg) uptake by crop plants and the availability of soil P, K, Ca and Mg. High levels of biochar application over the course of the crop rotation suppressed NH₃ volatilization in the rice season, but stimulated it in the wheat season.

Conclusions

Converting straw to biochar followed by successive application to soil is viable for soil C sequestration, CH₄ mitigation, improvements of soil and crop productivity. Biochar soil amendment influences NH₃ volatilization differently in the flooded rice and upland wheat seasons, respectively.     

The Enhancement of Soil Fertility,Dry Matter Transport and Accumulation,Nitrogen Uptake and Yield in Rice via Green Manuring

Readily available chemical fertilizers have resulted in a decline in the use of organic manure (e.g., green manures), a traditionally sustainable source of nutrients. Based on this, we applied urea at the rate of 270 kg ha⁻¹ with and without green manure in order to assess nitrogen (N) productivity in a double rice cropping system in 2017. In particular, treatment combinations were as follows: winter fallow rice-rice (WF-R-R), milk vetch rice-rice (MV-R-R), oil-seed rape rice-rice (R-R-R) and potato crop rice-rice (P-R-R). Results revealed that green manure significantly (p ≤ 0.05) improved the soil chemical properties and net soil organic carbon content increased by an average 117.47%, total nitrogen (N) by 28.41%, available N by 26.64%, total phosphorus (P) by 37.77%, available P by 20.48% and available potassium (K) by 33.10% than WF-R-R, however pH was reduced by 3.30% across the seasons. Similarly, net dry matter accumulation rate enhanced in green manure applied treatments and ranked in order: P-R-R > R-R-R > MV-R-R > WF-R-R. Furthermore, the total leaf dry matter transport (t ha⁻¹ ) for the P-R-R in both seasons was significantly higher by an average 11.2%, 7.2% and 36 % than MV-R-R, R-R-R, and WF-R-R, respectively. In addition, net total nitrogen accumulation (kg ha⁻¹ ) was found higher in green manure applied plots compared to the control. Yield and yield attributed traits were observed maximum in green manure applied plots, with treatments ranking as follows: P-R-R > R-R-R > MV-R-R > WF-R-R. Thus, results obtained highlight ability of green manure to sustainably improve soil quality and rice yield.     

Biochar in Combination with Nitrogen Fertilizer is a Technique: To Enhance Physiological and Morphological Traits of Rice (Oryza sativa L.) by Improving Soil Physio-biochemical Properties

The over use of synthetic nitrogen (N) fertilizers is the major anthropogenic cause of low N-use efficiency and environmental damage in wetland rice production. Biochar (B) addition to soil is suggested as a climate change mitigation tool that supports carbon sequestration and reduces N losses and greenhouse gas emissions from the soil. Therefore, this study assessed the effect of four levels of B (0, 10, 20 and 30 t ha^?1) combined with two levels of N (135 and 180 kg ha^?1) on soil health, roots dynamics, physiological attributes, and yield components of rice. The addition of B at 30 t ha^?1 combined with 135 N kg ha^?1 increased chlorophyll content, net photosynthetic rate, biomass, and grain yield by 104%, 64%, 12%, and 30%, respectively, over control. Further, root traits such as total root length (TRL), total root volume (TRV), total root surface area (TRSA), and total average root diameter (TARD) were improved under 30 t ha^?1 combined with 135 N kg ha^?1 by 20%, 13%, 13%, and 25%, respectively, than non-biochar treatment under lower N application. Improvements in these traits resulted from higher N uptake due to improved soil physiochemical properties and soil microbial biomass combined with biochar. Interestingly, enhanced N metabolizing enzyme activities, including nitrate reductase (NR), glutamine synthetase (GS), and glutamine oxoglutarate aminotransferase (GOGAT) in biochar-treated plots, further supported the increases in these traits. Our results revealed that the integration of 30 t B ha^?1 with 135 kg N ha^?1 is a favorable option for enhancing soil health and rice grain yield.

     

减氮配施稻秆生物炭对稻田土壤养分及植株氮素吸收的影响

通过2018年早稻和晚稻田间试验,研究化学氮肥减量及配施稻秆生物炭对稻田土壤养分特性及植株氮素吸收的影响。试验包括6个处理:不施氮(CK)、常规施氮(N₁₀₀)、减氮20%(N₈₀)、减氮20%配施生物炭(N₈₀+BC)、减氮40%(N₆₀)、减氮40%配施生物炭(N₆₀+BC)。结果表明: 与常规施氮相比,单纯减氮20%和40%或配施生物炭对早晚稻不同生育期土壤pH、有机质、全氮、铵态氮、全磷、有效磷、全钾、速效钾无显著影响;减氮20%配施生物炭显著增加晚稻分蘖期的土壤阳离子交换量(CEC),而减氮40%配施生物炭则显著增加晚稻抽穗期的电导率(EC)值。与单纯减氮相比,N₈₀+BC的土壤速效钾含量在早晚稻抽穗期均显著升高,土壤pH值、全氮在晚稻成熟期显著增加;N₆₀+BC的土壤全钾含量在早稻成熟期显著升高。不同处理早稻土壤硝态氮含量随生育进程逐渐降低,与分蘖期相比,抽穗期和成熟期的常规施氮土壤硝态氮含量分别降低50.0%和71.6%,而配施生物炭处理则降低6.3%～45.5%,减氮配施生物炭显著降低了硝态氮的流失。在晚稻抽穗期,减氮配施生物炭植株吸氮量显著高于常规施氮和单纯减氮,增加幅度为34.8%～52.4%。综上,适度的减氮或配施稻秆生物炭能有效保持土壤养分,促进水稻对氮素的吸收,提高氮素利用率。     

Role of nitrogen and magnesium for growth,yield and nutritional quality of radish

Nitrogen (N) affects all levels of plant function from metabolism to resource allocation, growth, and development and Magnesium (Mg) is a macronutrient that is necessary to both plant growth and health. Radish (Raphanus sativus L.) occupies an important position in the production and consumption of vegetables globally, but there are still many problems and challenges in its nutrient management. A pot trial was conducted to investigate the effects of nitrogen and magnesium fertilizers on radish during the year 2018–2019. Nitrogen and magnesium was applied at three rates (0, 0.200, and 0.300 g N kg⁻¹ soil) and (0, 0.050, and 0.100 g Mg kg⁻¹ soil) respectively. The experiment was laid out in a completely randomized design (CRD) and each treatment was replicated three times. Growth, yield and quality indicators of radish (plant height, root length, shoot length, plant weight, total soluble sugar, ascorbic acid, total soluble protein, crude fiber, etc.) were studied. The results indicated that different rates of nitrogen and magnesium fertilizer not only influence the growth dynamics and yields but also enhances radish quality. The results revealed that the growth, yield and nutrient contents of radish were increased at a range of 0.00 g N. kg⁻¹ soil to 0.300 g N. kg⁻¹ soil and 0.00 g Mg. kg⁻¹ soil to 0.050 g Mg. kg⁻¹ soil and then decreased gradually at a level of 0.100 g Mg. kg⁻¹ soil. In contrast, the crude fiber contents in radish decreased significantly with increasing nitrogen and magnesium level but increased significantly at Mg₂ level (0.050 g Mg. kg⁻¹ soil). The current study produced helpful results for increasing radish quality, decreasing production costs, and diminishing underground water contamination.     

不同有机无机复混肥对水稻产量和氮素利用率的影响

通过田间试验,研究了菜粕堆肥、猪粪堆肥和中药渣堆肥有机无机复混肥与化肥对常优1号水稻产量、氮素利用效率、土壤供氮特征以及土壤微生物多样性的影响.结果表明：各施氮肥处理的稻谷产量（7918.8～9449.2 kg·hm^-2）均显著高于对照（6947.9 kg·hm^-2）,其中有机无机复混肥处理的稻谷产量(8532.0～9449.2 kg·hm^-2)显著高于化肥处理（7918.8 kg·hm^-2）,比化肥处理增产7.7%～19.3%;菜粕堆肥、猪粪堆肥、中药渣堆肥有机无机复混肥处理的氮素积累量、氮素转运率、氮素回收率和氮肥农学利用效率及生理利用效率均显著高于化肥处理;有机无机复混肥处理明显提高了土壤矿质氮含量,改善了土壤供氮特性,提高了氮利用率;对各处理土壤DNA条带采用邻接法分析显示：5个处理土壤样品可分为三大族群,化肥与对照处理为第一族群,猪粪堆肥、中药渣堆肥处理为第二族群,菜粕堆肥处理属第三族群.表明施入外源有机物质(菜粕、猪粪与中药渣)可能会改变土壤的细菌群落结构,而施入化肥对土壤的细菌群落结构影响较小.     

生物炭对菜园土壤微生物功能多样性的影响

研究生物炭的施用及其与不同肥料混施对菜园土壤中微生物群落功能多样性的影响,为农业废弃物的合理利用和菜园土优化培肥提供科学依据和理论指导。以清远市连州县代表性菜园土(属肥熟旱耕人为土)为研究对象,通过盆栽试验,利用BIOLOG方法对10个施肥处理(对照CK(0%生物碳+无肥)、T1(0%生物碳+0.1%商品有机肥)、T2(0.1%生物碳+无肥)、T3(0.25%生物碳+无肥)、T4(0.5%生物碳+无肥)、T5(1%生物碳+无肥)、T6(100(N)+30(P_2O_5)+75(K_2O)mg/kg干土)、T7(0.1%生物碳+0.1%商品有机肥)、T8(0.1%生物碳+100(N)+0(P_2O_5)+75(K_2O)mg/kg干土)、T9(0.1%生物碳+100(N)+30(P_2O_5)+75(K_2O)mg/kg干土)、T10(0.1%生物碳+0.1%商品有机肥+100(N)+0(P_2O_5)+75(K_2O)mg/kg干土))的土壤微生物群落功能多样性进行分析。结果表明:(1)T1和T3处理比其它处理显著提高土壤微生物对碳源的利用率(P0.05),但生物炭施用量增加会降低平均颜色变化率(AWCD值);(2)T1处理可以显著提高土壤微生物的群落物种均匀度(Mclntosh指数),而T3处理显著提高土壤微生物的物种丰富度和均匀度(Shannon和Mclntosh指数);(3)T1和T3处理对聚合物类、碳水化合物类、羧酸类、氨基酸类和酚类碳源利用率最高;(4)添加化肥处理中磷肥的施用可以提高土壤微生物活性,增加土壤微生物碳源利用能力,而氮肥和钾肥的添加显著降低了土壤微生物的碳源利用能力;(5)主成分分析表明,T1、T2和T3处理的微生物碳代谢功能群结构相似;单施有机肥或适量生物炭对土壤微生物群落结构的影响较混合施用更为显著;化学磷肥的添加及在施用化肥的基础上配施适量生物炭改变了土壤微生物对碳源种类的利用。     

Effect of crop residues on root growth and phosphorus acquisition of pearl millet in an acid sandy soil in Niger

The effect of long-term (1983–1988) applications of crop residues (millet straw, 2–4 t ha^-1 yr^–1) and/or mineral fertilizer (30 kg N, 13 kg P and 25 kg K ha^-1 yr^-1) on uptake of phosphorus (P) and other nutrients, root growth and mycorrhizal colonization of pearl millet (Pennisetum glaucum L.) was examined for two seasons (1987 and 1988) on an acid sandy soil in Niger. Treatments of the long-term field experiment were: control (–CR–F), mineral fertilizer only (–CR+F), crop residues only (+CR–F), and crop residues plus mineral fertilizer (+CR+F).In both years, total P uptake was similar for +CR–F and –CR+F treatments (1.6–3.5 kg P ha^-1), although available soil P concentration (Bray I P) was considerably lower in +CR–F (3.2 mg P kg^-1 soil) than in –CR+F (7.4) soil. In the treatments with mineral fertilizers (–CR+F; +CR+F), crop residues increased available soil P concentrations (Bray I P) from 7.4 to 8.9 mg kg^-1 soil, while total P uptake increased from 3.6 to 10.6 kg P ha^-1. In 1987 (with 450 mm of rainfall), leaf P concentrations of 30-day-old millet plants were in the deficiency range, but highest in the +CR+F treatment. In 1988 (699 mm), leaf P concentrations were distinctly higher, and again highest in the +CR+F treatment. In the treatments without crop residues (–CR–F; –CR+F), potassium (K) concentrations in the leaves indicated K deficiency, while application of crop residues (+CR–F; +CR+F) substantially raised leaf K concentrations and total K uptake. Leaf concentrations of calcium (Ca) and magnesium (Mg) were hardly affected by the different treatments.In the topsoil (0–30 cm), root length density of millet plants was greater for +CR+F (6.5 cm cm^-3) than for +CR–F (4.5 cm cm^-3) and –CR+F (4.2 cm cm^-3) treatments. Below 30 cm soil depth, root length density of all treatments declined rapidly from about 0.6 cm cm^-3 (30–60 cm soil depth) to 0.2 cm cm^-3 (120–180 cm soil depth). During the period of high uptake rates of P (42–80 DAP), root colonization with vesicular-arbuscular mycorrhizal (VAM) fungi was low in 1987 (15–20%), but distinctly higher in 1988 (55–60%). Higher P uptake of +CR+F plants was related to a greater total root length in 0–30 cm and also to a higher P uptake rate per unit root length (P influx). Beneficial effects of crop residues on P uptake were primarily attributed to higher P mobility in the soil due to decreased concentrations of exchangeable Al, and enhancement of root growth. In contrast, the beneficial effect of crop residues on K uptake was caused by direct K supply with the millet straw.     

生物炭添加对不同水氮条件下芦苇生长和氮素吸收的影响

生物炭能改良土壤从而促进植物生长和氮素吸收，但其作用效果是否受水氮条件的影响尚不清楚。以湿地植物芦苇为研究对象，在3种氮添加水平（无添加，30 kg hm^-2 a^-1和60 kg hm^-2 a^-1）和两种水分（淹水和非淹水）条件下分别进行生物炭添加和不添加处理，结果表明：（1）生物炭添加能促进芦苇根系生长，在非淹水条件下根系生物量增加了40.5%，在淹水条件下根系生物量增加了20.1%。（2）生物炭添加能促进非淹水条件下芦苇的氮素吸收，能提高淹水条件下芦苇的氮素生产力。（3）生物炭添加加剧了土壤氮素损失，且在非淹水高氮条件下作用最强，可能是由于生物炭促进了芦苇的氮素吸收。芦苇氮素吸收速率与土壤氮损失之间存在显著的正相关关系。因此，在添加生物炭时，需要考虑土壤水分状况和氮素富集程度以及植物的氮素吸收偏好。该研究结果可为生物炭在湿地生态系统中的应用提供参考。     

The effects of biochars produced in different pyrolsis temperatures from agricultural wastes on cadmium uptake of tobacco plant

Abiotic stresses caused by cadmium (Cd) contamination in soil retard plant growth and decline the quality of food. Amendment of biochar was reported effective in reduction of mobility, plant uptake and toxicity of Cd in plants. The aim of this study was to investigate the effect of biochar applications produced from corn cob and rice husk at three different pyrolysis temperatures (400, 500 and 600 °C) on Cd uptake of tobacco plants. The results showed that the shoot Cd concentration and content of tobacco plants significantly increased with the application of Cd in increasing doses. The results showed that increasing Cd dosescaused significant increase (P < 0.01) in shoot Cd concentration and content of the tobacco plant at three different pyrolysis temperatures of both corn cob and rice husk biochars. The concentration of Cd was 0.48 mg kg^?1 in Cd0 dose of corn cob biochar produced at 500 °C and increased to 61.6 mg kg^?1 at Cd5, while Cd concentration increased to 72.3 mg kg^?1 with rice husk biochar. Despite the increase in Cd concentrations and content, shoot Cd concentrations and contents were significantly (P < 0.01) reduced with the treatments of corn cob and rice husk biochars produced at different pyrolysis temperatures. The Cd concentration at Cd5 dose in the absence of biochar addition was 90.5 mg kg^?1, while Cd concentration at Cd5 dose in 400, 500 and 600 °C treatments of corn cob biochar was reduced to 66.5, 61.6 and 67.3 mg kg^?1 respectively, and to 77.0, 72.3 and 70.2 mg kg^?1 in rice husk biochar. The results also revealed that corn cob biochar treatments were more effective in reducing Cd uptake of tobacco plants compared to rice husk biochar. Higher specific surface area of corncob biochar compared to rice husk biochar caused to the difference between two biochar sources on Cd uptake of tobacco plants.     

Microbial Dynamics and Diversity of Bacillus thuringiensis in Textile Effluent Polluted and Non-polluted Rice Field Soils of Orissa, India

Microbial diversity was assessed in the soils of non-polluted rice fields of Central Rice Research Institute and Choudwar, and textile effluent contaminated (about 30 years) rice fields of Choudwar about 4 years after cessation of pollution. The soils contained 0.62–1.01 % organic C and 0.07–0.12 % total N, and measured 6.18–8.24 pH and 0.6–2.68 mS/cm Eh which were more in the polluted Choudwar soil. The microbial populations (×10⁶ cfu/g soil) in the soils were: heterotrophs 1.21–10.9, spore formers 0.9–2.43, Gram (−)ve bacteria 4.11–8.0, nitrifiers 0.72–1.5, denitrifiers 0.72–2.43, phosphate solubilizers 0.14–0.9, asymbiotic nitrogen fixers 0.34–0.59, actinomycetes 0.07–0.11, fungi 0–0.5 and Bacillus thuringiensis (Bt) 0.4–0.61 which predominated in the polluted soil of Choudwar. The fungi were scarce in the polluted rice fields. The Bt isolates belonged to three motile and one non-motile group. Two motile Bt isolates were phenotyped as Bt subsp. sotto and israelensis, whereas, the non-motile isolate was Bt subsp. wahuensis. All Bt isolates produced extracellular protease, lipase and amylase enzymes. The microbial guilds had positive correlation among themselves, as well as, with soil physico-chemical characters but the fungi had negative relation and the nitrogen fixers were unrelated with the biotic and abiotic components.     

Root nutrient uptake enhances photosynthetic assimilation in prey-deprived carnivorous pitcher plant <Emphasis Type="Italic">Nepenthes talangensis</Emphasis>

Carnivorous plants grow in nutrient-poor habitats and obtain substantial amount of nitrogen from prey. Specialization toward carnivory may decrease the ability to utilize soil-derived sources of nutrients in some species. However, no such information exists for pitcher plants of the genus Nepenthes, nor the effect of nutrient uptake via the roots on photosynthesis in carnivorous plants is known. The principal aim of present study was to investigate, whether improved soil nutrient status increases photosynthetic efficiency in prey-deprived pitcher plant Nepenthes talangensis. Gas exchange and chlorophyll (Chl) fluorescence were measured simultaneously and were correlated with Chl and nitrogen concentration as well as with stable carbon isotope abundance (δ¹³C) in control and fertilized N. talangensis plants. Net photosynthetic rate (P _N) and maximum- (F_v/F_m) and effective quantum yield of photosystem II (Φ_PSII) were greater in the plants supplied with nutrients. Biomass, leaf nitrogen, and Chl (a+b) also increased in fertilized plants. In contrast, δ¹³C did not differ significantly between treatments indicating that intercellular concentration of CO₂ did not change. We can conclude that increased root nutrient uptake enhanced photosynthetic efficiency in prey-deprived N. talangensis plants. Thus, the roots of Nepenthes plants are functional and can obtain a substantial amount of nitrogen from the soil.     

Biochar can Increase Chinese Cabbage (<i>Brassica oleracea</i> L.) Yield,Decrease Nitrogen and Phosphorus Leaching Losses in Intensive Vegetable Soil

There are few evidences on the effect of biochar on vegetable yield, nitrogen (N) and phosphorus (P) leaching losses under intensive vegetable production soil. The current field plot scale study evaluated responses of Chinese cabbage (Brassica oleracea L.) yield, N and P leaching losses using five N treatments of common N application rate according to local farmers’ practice (N100%), reducing 20% or 40% N fertilizer (N80% and N60%), and reducing 40% N fertilizer but incorporating 10 or 20 t/ha biochar (N60% + BC10 and N60% + BC20). Results showed that N80% and N60% decreased both the cabbage economic and leaf yields by 6.8%–36.3% and 27.4%–37.7%, respectively. Incorporation of biochar with reduced N fertilizer rates improved the cabbage yield, in particular the N60% + BC20 matched the yield that observed in N100% treatment. Enhanced N and P uptake capacities of cabbage shoot probably contributed the higher vegetable production under both biochar amendment schemes. Biochar application mitigated the NH₄⁺-N and total P leaching losses by 20%–30% and 29%–32%, respectively, compared with their counterpart treatment N60%. Nevertheless, biochar exerted no influence on the NO₃^–-N leaching. In addition, soil organic matter content was recorded with 7.4%–28.7% higher following 10–20 t/ha biochar application. In conclusion, biochar application can increase economic yield of cabbage via increasing N and P use efficiency, decrease N and P leaching losses, and improve soil quality in an intensive vegetable production system.