Enhancing phosphorus availability,soil organic carbon,maize productivity and farm profitability through biochar and organic–inorganic fertilizers in an irrigated maize agroecosystem under semi‐arid climate

Biochar amendments offer promising potential to improve soil fertility, soil organic carbon (SOC) and crop yields; however, a limited research has explored these benefits of biochar in the arid and semi‐arid regions. This two‐year field study investigated the effects of Acacia tree biomass‐derived biochar, applied at 0 and 10 t ha^?1 rates with farmyard manure (FYM) or poultry manure (PM) and mineral phosphorus (P) fertilizer combinations (100 kg P ha^‐1), on maize (Zea mays L.) productivity, P use efficiency (PUE) and farm profitability. The application of biochar with organic–inorganic P fertilizers significantly increased soil P and SOC contents than the sole organic or inorganic P fertilizers. Addition of biochar and PM as 100% P source resulted in the highest soil P (104% increase over control) and SOC contents (203% higher than control). However, maize productivity and PUE were significantly higher under balanced P fertilizer (50% organic + 50% mineral fertilizer) with biochar and the increase was 110%, 94% and 170% than 100%‐FYM, 100%‐PM and 100% mineral fertilizer, respectively. Maize productivity and yield correlated significantly positively with soil P and SOC contents These positive effects were possibly due to the ability of biochar to improve soil properties, P availability from organic–inorganic fertilizers and SOC which resulted in higher PUE and maize productivity. Despite the significant positive relationship of PUE with net economic returns, biochar incorporation with PM and mineral fertilizer combination was economically profitable, whereas FYM along biochar was not profitable due to short duration of the field experiments.     

Effects of cotton (Gossypium hirsutum L.) straw and its biochar application on NH3 volatilization and N use efficiency in a drip-irrigated cotton field

Reducing ammonia (NH₃) volatilization is a practical way to increase nitrogen (N) fertilizer use efficiency (NUE). In this field study, soil was amended once with either cotton (Gossypium hirsutum L.) straw (6 t ha^?1) or its biochar (3.7 t ha^?1) unfertilized (0 kg N ha^?1) or fertilized (450 kg N ha^?1), and then soil inorganic N concentration and distribution, NH₃ volatilization, cotton yield and NUE were measured during the next two growing seasons. In unfertilized plots, NH₃ volatilization losses in the straw-amended and biochar-amended treatments were 38–40% and 42–46%, respectively, less than that in control (i.e., unamended soil) during the two growing seasons. In the fertilized plots, NH₃ volatilization losses in the straw-amended and biochar-amended treatments were 30–39% and 43–54%, respectively, less than that in the control. Straw amendment increased inorganic N concentrations, cotton yield, cotton N uptake and NUE during the first cropping season after application, but not during the second. In contrast, biochar increased cotton N uptake and NUE during both the first and the second cropping seasons after application. Furthermore, the effects of biochar on cotton N uptake and NUE were greater in the second year than in the first year. These results indicate that cotton straw and cotton straw biochar can both reduce NH₃ volatilization and also increase cotton yield, N uptake and NUE. In addition, the positive effects of one application of cotton straw biochar were more long-lasting than those of cotton straw.     

膜下滴灌制度与生物炭用量对玉米生长及水氮利用效率的影响

为探明干旱地区盐碱地膜下滴灌不同灌水下限施用生物炭对玉米产量和水肥利用效率的响应差异及相互影响关系,提出较优的灌溉制度和生物炭用量。连续2年在河套灌区盐渍化农田玉米生长阶段进行小区控制试验,设计3个灌水下限[土壤基质势为-15(W15),-25(W25),-35(W35)kPa,灌水定额为22.5 mm]和3个生物炭用量水平[0(B0),15(B15),30(B30)t/hm²],2因素完全随机试验设计,共9个处理。测定并分析玉米全生育期0—15 cm土壤理化性状、作物生长特征和水氮利用效率。结果表明：不同灌水下限施用生物炭整体提高玉米全生育期土壤含水率、有机质和碱解氮含量,同一灌溉水平下生物炭用量越高,各指标提升的幅度越大。施用生物炭提高玉米地上部干物质积累量和产量,灌溉水利用效率和氮肥偏生产力显著提高,且生物炭施用当年的效果普遍优于翌年。相较于不施用生物炭的对照,W15、W25、W35条件下,B15使玉米产量平均增加12.8%,10.3%,14.2%,灌溉水利用效率提高14.2%,10.4%,12.9%,氮肥偏生产力提升12.8%,10.4%,14.0%,其节...     

Chemically and biologically activated biochars slow down urea hydrolysis and improve nitrogen use efficiency

Biochar is considered a potential technology to enhance chemical fertilizer use efficiency through intensification of the interactions between nutrients and the functional groups on biochar surfaces. However, little is known about how the application of activated biochars mixed with urea influences nitrogen(N) mineralization and crop performance in paddy fields. Here, a sawdust-derived fresh biochar (FBC)(ca. 400?C) was activated chemically with 15%hydrogen peroxide and biologically with a nutri...     

15N示踪法研究生物炭施用对水稻—土壤系统氮肥去向的影响

为探究施用水稻秸秆生物炭对水稻产量、氮肥利用率、氮肥残留及损失的影响,采用盆栽试验结合¹⁵N示踪技术,分析了施用水稻秸秆生物炭对水稻生物量、氮素积累量、肥料氮去向以及氨氧化微生物的影响。研究共设置5个处理:不施氮肥(N0)、单施化肥(CF)、施化肥配施0.5%生物炭(BC1)、施化肥配施1%生物炭(BC2)和施化肥配施2%生物炭(BC3)。结果表明:与CF处理相比,BC2和BC3处理均显著提高水稻产量,增产率分别为19.3%和22.0%。施用生物炭显著增加水稻氮素积累量和表观利用率。施用生物炭的水稻籽粒肥料氮积累和总肥料氮积累量较CF处理分别提高18.6%~23.4%和18.5%~26.5%。然而,施用生物炭处理与CF处理之间的籽粒土壤氮吸收量没有显著差异。BC1、BC2和BC3处理的氮肥利用率分别为30.4%,28.5%和29.3%,均显著高于CF处理(24.1%)。施用生物炭有利于肥料氮在土壤中的 残留,从而减少损失。因此,施用生物炭的肥料氮损失率(25.7%~27.5%)显著低于单施化肥处理(38.4%)。与CF处理相比,高量施用生物炭(BC3)显著降低氨氧化细菌的amoA基因拷贝数,但施用生物炭对氨氧化古菌丰度没有显著影响。综上表明,施用水稻秸秆生物炭是提高水稻产量和氮肥利用率,同时还是有效减少氮素损失的一种有效措施。     

Impact of biochars on swell–shrinkage behavior,mechanical strength,and surface cracking of clayey soil

Swell–shrinkage, cracking and stickiness of expansive clayey soils usually lead to their low yield. Improvement of these poor soil physical properties is a key goal for enhancing the crop productivity of expansive clayey soils. This article presents results of a study on the impact of three biochars produced from wheat straw (SB), woodchips (WCB), and wastewater sludge (WSB) on the swell–shrinkage behavior, mechanical strength, and surface cracking of a clayey soil. The soil was treated with biochars at the rate of 0, 20, 40, and 60 g biochar kg^?1 soil, respectively; and incubated for 180 d in glasshouse. Application of biochars decreased significantly (p < 0.01) the coefficient of linear extensibility (COLE) of the soil, the effect of SB being most prominent. The tensile strength (TS) of the clayey soil was originally 937 kPa, which decreased to 458 kPa, 495 kPa and 659 kPa for 6% SB‐, WCB‐, and WSB‐amended soils, respectively. Shear strength tests indicated that biochars significantly reduced cohesion (c) and increased internal friction angle (θ). Biochar significantly reduced the formation of soil surface cracks, surface area, and length of the cracks. The surface area density of cracks in the 6% biochar‐amended soils decreased by 14% for SB, 17% for WCB, and 19% for WSB, respectively, compared with control. The results suggest that biochar can be used as a soil amendment for improving the poor physical properties of the clayey soil, particularly in terms of reduction in swell–shrinkage, tensile strength and surface area density of cracking.     

夏玉米污水灌溉时水分与氮素利用效率的研究

用田间实验研究污水灌溉条件下夏玉米水分与氮素的利用效率。试验设置了高、中、低3个不同灌水水平下的9个对比处理，结果表明：灌水量、灌溉水质、施肥量对夏玉米叶面积指数、株高和产量的影响很小；不同灌溉水量条件下，污水灌溉夏玉米的耗水规律与清水灌溉的耗水规律十分接近，且累积耗水量随灌溉水量的增大而增加；水分利用效率与灌溉水质和施肥无关，仅随灌溉水量的增加而减少。清水灌溉处理玉米的吸氮量高于污水灌溉处理玉米的吸氮量；氮的利用效率与灌水量和施肥无关，仅与灌溉水质有关，且污水灌溉氮的利用效率高于清水灌溉氮的利用效率。     

Developing nitrogen management strategies under drip fertigation for wheat and maize production in the North China Plain based on a 3‐year field experiment

The intensive winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) cropping systems in the North China Plain (NCP) rely on the heavy use of mineral nitrogen (N) fertilizers. As the fertigated area of wheat and maize in the NCP has grown rapidly during recent years, developing N management strategies is required for sustainable wheat and maize production. Field experiments were conducted in Hebei Province during three consecutive growth seasons in 2012–2015 to assess the influence of different N fertigation rates on N uptake, yield, and nitrogen use efficiency [NUE: recovery efficiency (RE_N) and agronomic efficiency (AE_N)]. Five levels of N application, 0 (FN₀), 40 (FN_40%), 70 (FN_70%), 100 (FN_100%), and 130% (FN_130%) of the farmer practice rate (FP: 250 kg N ha^?1 and 205.5 kg N ha^?1 for wheat and maize, respectively), corresponding to 0, 182.2, 318.9, 455.5, and 592.2 kg N ha^?1 y^?1, respectively, were tested. Nitrogen in the form of urea was dissolved in irrigation water and split into six and four applications for wheat and maize, respectively. In addition, the treatment “drip irrigation + 100% N conventional broadcasting” (DN_100%) was also conducted. All treatments were arranged in a randomized complete block design with three replications. The results revealed the significant influence of both N fertigation rate and N application method on grain yield and NUE. Compared to DN_100%, FN_100% significantly increased the 3‐year averaged N recovery efficiency (RE_N) by 0.09 kg kg^?1 and 0.04 kg kg^?1, and the 3‐year averaged N agronomic efficiency (AE_N) by 2.43 kg kg^?1 and 1.62 kg kg^?1 for wheat and maize, respectively. Among N fertigation rates, there was no significant increase in grain yield in response to N applied at a greater rate than 70% of FP due to excess N accumulation in vegetative tissues. Compared to FN_70%, FN_100%, and FN_130%, FN_40% increased the RE_N by 0.17–0.57 kg kg^?1 and 0.03–0.34 kg kg^?1and the AE_N by 4.60–27.56 kg kg^?1 and 2.40–10.62 kg kg^?1 for wheat and maize, respectively. Based on a linear‐response relationship between the N fertigation rate and grain yield over three rotational periods it can be concluded that recommended N rates under drip fertigation with optimum split applications can be reduced to 46% (114.6 kg N ha^?1) and 58% (116.6 kg N ha^?1) of FP for wheat and maize, respectively, without negatively affecting grain yield, thereby increasing NUE.     

Physicochemical Characteristics of Biochars Derived From Corn,Hardwood, Miscanthus,and Horse Manure Biomasses

Biochar, a carbon-rich by-product of biomass pyrolysis, is widely recognized as a potential ingredient for soil amendment, fertility, and carbon sequestration owing to its favorable physicochemical properties. The objective of this study was to investigate the chemical and physical properties of biochars produced through pyrolysis at 450°C from agricultural residues available in Northwest Missouri, namely hardwood (HW), corn stover (CR), miscanthus (MS), and horse manure (HM). These properties were assessed through the analysis of pyrolysis yield, pH, volatile matter, fixed carbon, ash and carbon (C), hydrogen (H), sulfur (S), nitrogen (N) contents, trace metal concentrations, surface morphology, surface functional groups, bulk density, and water holding capacity. The biochars derived from HW, MS and CR materials showed high volatile-matter (33–42%), high fixed carbon contents (42–47%), very low ash contents (6–15%), and low bulk density (0.14–0.28 g cm^?3) as compared to that of HM. A wide range of trace elements was observed in biochar samples with significant differences in concentrations. In addition, CR, HW and MS biochars displayed a disordered graphitic-like structure with well-developed pores and surface areas of 23, 70 and 90 m²/g respectively, and high water-holding capacity up to 750%, indicating their potential application as a soil amendment.     

Effect of biochar applied with plant growth-promoting rhizobacteria (PGPR) on soil microbial community composition and nitrogen utilization in tomato

Plant growth-promoting rhizobacteria (PGPR) represent an important microbial community group and have beneficial effects on plant growth and development. A pot experiment was conducted to study the effect of biochar applied with PGPR on the soil microbial community composition and nitrogen use efficiency (NUE) of tomato, which could provide a theoretical basis for rational fertilization. Six treatments were designed: no nitrogen (N), PGPR, or biochar control (CK); biochar without N or PGPR (BCK); N without PGPR or biochar (U); N and PGPR without biochar (UP); N and biochar without PGPR (UB); and N, PGPR, and biochar (UBP). The tomato yield in the UP treatment was 9.09% lower than that in the U treatment, whereas that in the UB treatment was 19.93% higher than that in the U treatment. The tomato yield in the UBP treatment was 32.45%, 45.69%, and 10.44% higher than those in the U, UP, and UB treatments, respectively. Biochar combined with PGPR increased the relative abundance of Nitrospira and Bradyrhizobium in the soil. At the tomato maturity stage, the soil NO₃^--N content in the UBP treatment was 87.12%, 88.12%, and 31.04% higher than those in the U, UP, and UB treatments, respectively. The NUE in the UP treatment was 4.03% lower than that in the U treatment, and that in the UBP treatment was 13.63%, 17.66%, and 10.77% higher than those in the U, UP, and UB treatments, respectively. This study showed that biochar combined with PGPR can improve soil microbial community structure and increase the NUE of tomato.     

Biochars influence sweet‐potato yield and nutrient uptake in tropical Papua New Guinea

Currently, the biomass of an invasive and obnoxious weed, kunai grass (Imperata cylindrica), is uncontrollably burnt in Papua New Guinea in subsistence farming systems resulting in unwarranted negative environmental consequences. We explored the possibility of sustainable utilization of biochar produced from the weed biomass along with a standard feedstock‐rice husk (Oryza sativa). Biochars were produced with lab‐scale pyrolysis at 550°C, characterized for chemical properties and plant nutrient composition. Further, agronomic efficacy of soil incorporation of biochars (5 t ha^?1) or co‐applied with mineral fertilizers (100, 11, and 62 kg ha^?1 N, P, K, respectively) was tested for sweet potato (Ipomoea batatas L. Lam) in a field experiment. The two biochars differed significantly (P < 5%) with respect to recovery from the feedstocks, chemical characters and nutrient composition. Kunai grass biochar was poorer in nutrients (< 1%) with distinctly alkaline pH and higher electrical conductivity. Biochar amendment to soil showed significant (P < 5%) improvement of soil moisture, while co‐application of biochars along with mineral fertilizers showed soil moisture decrease. Biochar amendment improved the growth parameters and total tuber yield of sweet potato by about 20%, while co‐application with mineral fertilizers augmented total tuber yield by 100% and above‐ground biomass yields by > 75%. Besides, improving agronomic performance of sweet potato crop, co‐application of biochars with mineral fertilizers enhanced uptake of N, P, K, Ca, Mg, and S. Production and utilization of biochar in sweet‐potato production could offer an efficient means of disposing biomass of kunai grass with concomitant productivity improvement in Papua New Guinea.     

Yield and water use efficiency of hybrid Bt cotton as affected by methods of sowing and rates of nitrogen under surface drip irrigation

Field experiments were conducted for two years to find out the appropriate sowing configuration and rate of nitrogen (N) for sustained yield and improved water use efficiency of hybrid Bt cotton irrigated through surface drip irrigation. Drip irrigation under normal sowing, in which equal quantities of water and N were applied as check-basin irrigation, resulted in an increase of 389 and 155 kg ha^?1 in seed cotton yield compared with check-basin irrigation during the first and second year, respectively. Normal paired row sowing under a drip irrigation system, in which only 50% of irrigation water was applied compared with normal sowing, produced a yield similar to normal sowing under drip irrigation during both years, resulting in 22% higher water use efficiency. Dense paired row sowing under drip irrigation, in which only 75% irrigation water was applied compared with normal sowing, increased the mean seed cotton yield by 5% and water use efficiency by 19%. Decrease in the rate of nitrogen application (from 150 to 75 kg N ha^?1) caused a decline in seed cotton yield and water use efficiency under all the methods of sowing, but the reverse was true for agronomic efficiency of N.     

Impact of integrated application of biochar and nitrogen fertilizers on maize growth and nitrogen recovery in alkaline calcareous soil

Biochar application has been considered as a rich source of carbon which helps to improve the physico-chemical properties and fertility of the soil. In Pakistan, excessive use of nitrogen fertilizer is considered a serious problem, so it is of vital importance to examine the effect of biochar on soil with varying doses of nitrogen fertilizer. We hypothesized that addition of biochar to an alkaline calcareous soil could improve not only soil quality and crop yield but also nitrogen use efficiency (NUE), reducing the loss of nitrogen (N) in the form of denitrification, ammonia volatilization, and nitrate leaching. A pot experiment was conducted under 2-factorial completely randomized design having three replications to evaluate the NUE in biochar amended calcareous soil. Biochar was applied at the rate of 0%, 1% and 2% (w/w) in pots filled with 17 kg of soil using various levels of N (0%, 50% and 100% of recommended dose) on maize (Zea mays L.). Several soil quality indicators, uptake, and yield of maize were monitored. Biochar application significantly decreased soil pH, increased water-holding capacity, total organic carbon, maize yield, stomatal conductance, and nitrogen uptake in plant. The results of the study indicated that addition of biochar could not only decrease the use of inorganic fertilizers by improving its quality and yield as in our case biochar at the rate of 1% and N at the rate of 50% provided optimum output minimizing the economic cost eventually.     

Biochars improve aggregate stability,water retention,and pore‐space properties of clayey soil

The influence of biochar amendments on the physical quality of a clayey soil (Vertisol) was evaluated by aggregate‐size distribution and stability, water retention, and pore‐space structure of biochar‐amended soils. Clayey soil was treated with three kinds of biochars (straw biochar, woodchips biochar, and wastewater‐sludge biochar) at the rate of 0, 20, 40, and 60 g biochar (kg soil)^–1 and incubated for 180 d in glasshouse. The application of straw biochar (SB) and wastewater‐sludge biochar (WSB) significantly enhanced the formation of 5–2 and 0.25–0.5 mm macroaggregates in the clayey soil relative to the control treatment, while the < 0.25‐cm microaggregate decreased with biochar additions. However, woodchips biochar (WCB) had no obvious effect on the formation of macroaggregate. The application of SB and WSB increased the mean weight diameter (MWD) and geometric mean diameter (GMD) of clayey soil, implying that biochar increased the aggregate stability. They improved the aggregate stability through an enhanced resistance to slaking and increased interparticular cohesion. The SB‐amended soils exhibited significant increases in the available water contents of soils. The application of SB significantly increased pore volume in the macropore (> 75 μm) and mesopore (30–75 μm) ranges, which may be the result of the reorganization of pore‐size distribution and aggregation processes induced by the addition of biochar. Results indicated that biochar had the potential to improve the physical quality and pore‐space status of clayey soil. It is suggested that biochar may be considered as a soil amendment for improving poor physical characteristics of clayey soil.     

Adapting and evaluating APSIM-SoilP-Wheat model for response to phosphorus under rainfed conditions of Pakistan

Phosphorus (P) treatments were used to evaluate APSIM-SoilP-Wheat model and phosphorus use efficiency (PUE) of two wheat cultivars (NARC-2009 and Chakwal-50) during 2011–2013. Overall, the Agricultural Production Systems Simulator (APSIM) model accurately simulated dry matter, grains per spike, grain yield, biomass P, and grain P for two years, for both genotypes in response to all P fertilizer treatments. NARC-2009 had 55% higher PUE compared to Chakwal-50. Information on PUE will be helpful in breeding high PUE cultivars. Modeling results showed that the production of wheat depends on growth as well as on P uptake of the plants. The close agreement between observed and simulated results confirmed the accuracy of the model which was validated with skill scores like R² and RMSE. APSIM simulation proved to be valuable tool to evaluate PUE under rainfed conditions.     

生物质炭施用对马铃薯产量和品质的影响

通过田间试验,观测分析不同生物质炭用量(0、20和40 t/hm~2)下马铃薯产量、品质和土壤肥力的变化及其年际效应,为生物质炭在马铃薯生产过程中的应用提供理论依据。结果表明,低剂量生物质炭施用(20 t/hm~2)显著提高了马铃薯总产量和商品率,生物质炭施用后第一年马铃薯总产量比对照提高了41.08%。当生物质炭用量为40 t/hm~2时,马铃薯产量与对照没有显著差异但降低了一些品质指标,其中2016年干物质和淀粉含量比对照降低了18.47%和24.03%。生物质炭施用显著提高了土壤有机碳、有效磷和速效钾含量,并增加了土壤C/N和电导率;而对土壤p H和全氮含量的影响与生物质炭施用年限有关。生物质炭施用量和施用年限显著影响马铃薯产量和品质。低剂量生物质炭施用能显著提高马铃薯产量,但第二年无增产效果;随着生物质炭用量增加马铃薯增产效果消失,还可能会降低马铃薯品质。生物质炭施用后马铃薯产量变化与土壤紧实度改善无必然联系。     

Potato yield response to foliar application of phosphorus as affected by soil moisture and available soil phosphorus

Abstract

Foliar application of phosphorus (P) may be a supplementary treatment to sustain adequate P-status of potato (Solanum tuberosum L.). However, the prediction of the potential benefits of foliar P supply is difficult, since several factors, such as weather conditions and plant P-status influence the effects. We determined the impact of soil moisture and soil P-supply on the responsiveness to foliar P-application under controlled environmental conditions. Plant dry matter yields, P-accumulation and phosphorus use efficiency (PUE) with or without foliar application were determined at five soil P-levels in combination with two soil moisture levels. The results suggest that water status is of importance for the responsiveness to foliar P-application and may be related to diffusion of P through the leaf cells, which require a good water status. The PUE was significantly improved with irrigation while adding P to the soil decreased the PUE.     

Optimization of nitrogen fertilizer rate under integrated rice management in a hilly area of Southwest China

China has the world''s highest nitrogen (N) application rate, and the lowest N use efficiency (NUE). With the crop yield increasing, serious N pollution is also caused. An in-situ field experiment (2011-2015) was conducted to examine the effects of three N levels, 0 (i.e., no fertilizer N addition to soil), 120, and 180 kg N ha^-1, using integrated rice management (IRM). We investigated rice yield, aboveground N uptake, and soil surface N budget in a hilly region of Southwest China. Compared to traditional rice management (TRM), IRM integrated raised beds, plastic mulch, furrow irrigation, and triangular transplanting, which significantly improved rice grain yield, straw biomass, aboveground N uptake, and NUE. Integrated rice management significantly improved ¹⁵N recovery efficiency (by 10%) and significantly reduced the ratio of potential ¹⁵N loss (by 8%-12%). Among all treatments, the 120 kg N ha^-1 level under IRM achieved the highest ¹⁵N recovery efficiency (32%) and ¹⁵N residual efficiency (29%), with the lowest ¹⁵N loss ratio (39%). After rice harvest, the residual N fertilizer did not achieve a full replenishment of soil N consumption, as the replenishing effect was insufficient (ranging from -31 to -49 kg N ha^-1). Furthermore, soil surface N budget showed a surplus (69-146 kg N ha^-1) under all treatments, and the N surplus was lower under IRM than TRM. These results indicate IRM as a reliable and stable method for high rice yield and high NUE, while exerting a minor risk of N loss. In the hilly area of Southwest China, the optimized N fertilizer application rate under IRM was found to be 100-150 kg N ha^-1.     

土壤扩蓄增容肥对冬小麦棵间蒸发和水分利用效率的影响

利用农田水量平衡公式计算了冬小麦耗水量,用微型蒸渗仪测定了农田土壤棵间蒸发状况,在此基础上通过对比试验研究了土壤扩蓄增容肥条件下不同水分处理冬小麦生长期间农田棵间蒸发与水分利用效率.结果表明,施加土壤扩蓄增容肥后冬小麦生育期平均耗水量较对照平均减少了491.67 m3/h㎡,可明显降低冬小麦棵间蒸发,同时可降低播种到拔节期阶段棵间蒸发占阶段耗水量的比例;灌水量2250 m3/h㎡3理(T2)水分利用效率达2.62 kg/m3;灌水量1950 m3/h㎡的处理(T3)可增产32.68%.     

Positive and negative carbon mineralization priming effects among a variety of biochar-amended soils

Pyrogenic carbon (biochar) amendment is increasingly discussed as a method to increase soil fertility while sequestering atmospheric carbon (C). However, both increased and decreased C mineralization has been observed following biochar additions to soils. In an effort to better understand the interaction of pyrogenic C and soil organic matter (OM), a range of Florida soils were incubated with a range of laboratory-produced biochars and CO₂ evolution was measured over more than one year. More C was released from biochar-amended than from non-amended soils and cumulative mineralized C generally increased with decreasing biomass combustion temperature and from hardwood to grass biochars, similar to the pattern of biochar lability previously determined from separate incubations of biochar alone.The interactive effects of biochar addition to soil on CO₂ evolution (priming) were evaluated by comparing the additive CO₂ release expected from separate incubations of soil and biochar with that actually measured from corresponding biochar and soil mixtures. Priming direction (positive or negative for C mineralization stimulation or suppression, respectively) and magnitude varied with soil and biochar type, ranging from −52 to 89% at the end of 1 year. In general, C mineralization was greater than expected (positive priming) for soils combined with biochars produced at low temperatures (250 and 400 °C) and from grasses, particularly during the early incubation stage (first 90 d) and in soils of lower organic C content. It contrast, C mineralization was generally less than expected (negative priming) for soils combined with biochars produced at high temperatures (525 and 650 °C) and from hard woods, particularly during the later incubation stage (250-500 d). Measurements of the stable isotopic signature of respired CO₂ indicated that, for grass biochars at least, it was predominantly pyrogenic C mineralization that was stimulated during early incubation and soil C mineralization that was suppressed during later incubation stages. It is hypothesized that the presence of soil OM stimulated the co-mineralization of the more labile components of biochar over the short term. The data strongly suggests, however, that over the long term, biochar-soil interaction will enhance soil C storage via the processes of OM sorption to biochar and physical protection.