Preliminary studies on triticale,wheat, barley,and rye responses to lime and N.

Abstract

The lime and N requirements for triticale (X Triticosecale Wittmack) have not been established because of the relatively short history of the crop. This study was designed to evaluate the effects of lime and high N rates on triticale, wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and rye (Secale cereale L.) on Dickson silt loam (Typic Paleudult) and Decatur silty clay loam (Rhodic Paleudult) in 1974–1976. The soils had pH values of 4.9 and 5.5 with no lime and 5.4 and 5.8, respectively, when limed as recommended. The fertilizer rates were 112, 140, and 170 kg N/ha. Yields and N, P, K, Ca, Mg, Mn, Fe, Al, Zn, Cu, and B were determined in straw and grain. Liming the Dickson soil increased the straw yields of barley at 112 kg N/ha and grain yields of the cultivars generally at the 170 kg N/ha rate. Liming the Decatur soil did not have consistent effects on straw yields but increased the grain yields of the wheat and rye cultivars. Increasing N rate increased the straw yields of wheat on Dickson but decreased the grain yields of barley in the same soil with no lime. Nitrogen fertilization did not have consistent effects on the Decatur soil. The N, P, K, Ca, Mg, and Mn compositions suggested that more differences occured at the species level than at the cultivar level.     

Comparison of potential potassium leaching associated with organic and inorganic potassium sources in different arable soils in China

Potassium (K) leaching is detrimental to the maintenance of sustainable arable soil K fertility,especially in low-K fixation soils.It is not known whether the application of inorganic fertilizers with lower K mobility or crop straw can reduce potential K leaching in low-K fixation arable soils.The potential K leaching of 14 representative arable soils with different K fixation capacities in China was evaluated with or without the addition of K under two rainfall intensities (90 and 225 mm),and then potential K leaching was assessed in relation to five K sources (KCl,K₂SO₄,KH₂PO₄,maize (Zea mays L.) straw,and rice (Oryza sativa L.) straw).Without K addition,K leaching mainly occurred in sandy soils at 90 mm of rainfall and in soils with greater organic matter at225 mm of rainfall.With K addition,the leaching percentage of exogenous K ranged from 0.6%to 11.6%at 90 mm of rainfall and 1.2%to 21.2%at 225 mm of rainfall.The greatest K leaching occurred in soils with fewer K-bearing minerals and lower pH at both rainfall intensities.In most cases,KH₂PO₄,which has lower K mobility,markedly reduced K leaching in both high-and low-K leaching soils at the two rainfall intensities.Maize and rice straw reduced K leaching only in soils with high K leaching,regardless of rainfall amount,whereas more K was leached in soils with lower K leaching at high rainfall intensity.In conclusion,KH₂PO₄ and straw should be preferred for reducing K leaching in low-K fixation arable soils.     

Effect of organic residue amendment on mineralization of nitrogen in flooded rice soils under laboratory conditions

Abstract

This study was undertaken to assess the mineralization of nitrogen (N) in rice soils amended with organic residues under flooded condition. A lab incubation study with a 3x3 factorial design (two replications) was conducted with three rice soils (Joydebpur, Faridpur, and Thakurgaon) receiving the following treatments: 1) control, 2) rice straw (Oryza sativa L.), or 3) pea vine (Pisum sativum L.). The organic residue (25 mg straw g^‐1 soil) was mixed with soil and glass beads (1:1, soil to beads ratio), and transferred into a Pyrex leaching tube, flooded and then incubated at 35°C for up to 12 weeks. The soils in the leaching tubes were leached (while maintaining flooded condition) at 1,2,4, 8, and 12 weeks with deionized water for determination of NH₄‐N, NO₃‐N, pH, and Eh. Nitrogen mineralization in soils amended with rice straw was somewhat different than that of soils treated with pea vine. Soil treated with rice straw had a higher N mineralization rate than soils treated with pea vine, which was due to a lower carbon (C):N ratio for rice straw. The potentially mineralizable N pool (N_o) in soils amended with rice straw and pea vine under flooded conditions, estimated using a 1st order exponential equation, were 7 to 15 times, and 3 to 9 times greater for rice straw N_o values and pea vine, respectively, than the control. The K_N values for unamended soils ranged from 0.35 to 0.52 mg N kg^‐1 wk^‐1 and rice straw and pea vine treated soils were from 0.75 to 1.22 and 0.46 to 0.58 mgN kg^‐1 wk^‐1. The lower N_o and K_N values in pea vine treatments suggested there was greater immobilization of N than in rice straw treatments.     

Effect of gypsum on soil potassium and magnesium status and growth of alfalfa

Abstract

Though surface‐applied gypsum has been shown to be useful in reducing the subsoil acidity syndrome, excessive application could reduce the availability of other essential cations in soil. This study was conducted to determine the effects of surface‐applied gypsum on the availability of potassium (K) and magnesium (Mg) in field soils. Field experiments were conducted on Davidson and Tifton series soils in the southeastern United States with 6 main ameliorant treatments (0, 2, 5, and 10 t gypsum/ha, soil profile mixed to 1 m without lime incorporation and, mixed with lime to 1‐m depth), and 2 levels of Mg (0 and 100 kg Mg/ha) and 4 levels of K (0, 125, 250, and 375 kg K/ha) in a split‐split plot configuration. Alfalfa was grown on the Tifton soil and sorghum on the Davidson soil. Yields of alfalfa and sorghum increased with 2 t gypsum/ha but were adversely affected above 5 t gypsum/ha. Gypsum amendment at 2 t/ha reduced topsoil exchangeable Mg and K in both soils. In the soil profile study, exchangeable Mg was reduced throughout the upper 52.5‐cm depth, while no reduction of K was observed below the 22.5‐cm depth in either soil. The study indicates that Mg is more susceptible to leaching loss than K after surface application of gypsum. It is also suggested that surface‐applied gypsum be used as a soil ameliorant along with proper management of Mg and K fertilizers.     

Remediation of Cadmium Pollution in Soils by Different Amendments: A Column Study

Abstract

A column study was conducted to determine the effect of city compost, lime, gypsum, and phosphate on cadmium (Cd) mobility in three well‐recognized benchmark soils of India [viz., (Islamnagar) Vertisol, (Amarpur) Inceptisol, and (Khala) Alfisol]. Columns made of PVC were filled with soil treated with different treatment doses [viz., 0.5% city compost, 1% city compost, 2% city compost, 2.5 t lime/ha, 5 t lime/ha, 2.5 t lime/ha+0.5% city compost, 2.5 t gypsum/ha, 2.5 t gypsum/ha+0.5% city compost, and 100 kg P₂O₅/ha as potassium phosphate (KH₂PO₄). The columns were leached with 100 mg L^?1 Cd under saturated condition. The amount of water moving through the soils was measured as the pore volume. A delayed breakthrough curve (BTC) of Cd in the presence of lime has been observed in all the studied benchmark soil series. Among the treatments, lime application reduced the movement of Cd from surface soil to lower depth of soil to a large extent resulted in 9, 25, and 45% more retention of Cd in surface soil of the Islamnagar, Amarpur, and Khala series respectively. Explanation for reduced Cd mobility in limed soil can be derived from pH changes of soils. In comparison to control soil, phosphate application caused 6, 21, and 30% more retention of Cd in surface soil in the Islamnagar, Amarpur, and Khala series, respectively. Combined application of lime and city compost reduced the movement of Cd in the soil profile. It appears that organic matter controls the sorption of Cd in soils. The amount of Cd sorbed increased with increasing organic carbon content, but gypsum application may leach Cd beyond the root‐zone depth. A rapid breakthrough curve was observed under gypsum‐treated soils. Retardation factor revealed that a somewhat lower degree of Cd retention occurred in the Khala series, which might possibly be attributed to less clay content and low pH. Overall, the column study indicated that total Cd accumulation occurred up to depths of 5–7.5 cm, 7.5–10 cm, and 10–15 cm in soils of Islamnagar, Amarpur, and Khala series, respectively.     

5年定位试验条件下钾肥用量对双季稻产量和施钾效应的影响

通过5年定位试验（2008~2012年）, 研究不同钾肥施用量对水稻产量、植株钾素含量、钾素积累量、钾肥利用率、土壤钾素含量、钾素平衡和钾肥经济效益的影响。试验施钾量（K2O）从低到高设K0（不施钾）、K1（早稻84 kg/hm2、晚稻105 kg/hm2）、K2（早稻120kg/hm2、晚稻 150 kg/hm2）、K3（早稻156kg/hm2、晚稻195 kg/hm2）和K4（早稻192kg/hm2、晚稻 240kg/hm2）5个处理。5年的试验结果表明, 施钾能显著提高早、晚稻产量,在一定施钾量范围内,水稻产量随施钾量的增加而增加;施钾能促进水稻植株对钾素的吸收和积累,尤其是稻草对钾素的吸收和积累;早、晚稻的钾肥农学效应均以K2处理最高（早稻3.12 kg/kg、晚稻3.70 kg/kg）;钾肥利用率以K1处理最高（早稻41.2%、晚稻76.4%）,并随施钾量提高而降低;不同施钾量对土壤钾素含量有明显影响,土壤速效钾、缓效钾和土壤全钾均随施钾量的增加而增加,且不同处理间土壤速效钾含量差异达极显著水平（P＜0.01）;连续种植5年10季水稻后,K0、K1和K2处理的土壤钾素亏缺（K 127.1kg/hm2、 58.3kg/hm2和10.8kg/hm2）,亏缺量随施钾量的增加而降低; K3和K4处理的土壤钾素盈余（48.0 kg/hm2 和109.2kg/hm2）,盈余量随施钾量的增加而增加。在经济效益上,早、晚稻产投比均以K2处理最高（早稻1.04、晚稻1.27）。综合考虑施钾的增产效应、经济效益和土壤钾素养分平衡等因素,建议该双季稻区早稻施钾量在K2O 120~156 kg/hm2、晚稻施钾量在K2O 150~195kg/hm2范围内较为适宜。     

Agronomic evaluation of phosphate rock and slag on an upata acid soil in Bolivar State,Venezuela

Abstract

An agronomic evaluation of phosphate rock and slag on the acid soils of Upata, Bolivar State was conducted to measure their effect on the chemical properties of the soil and growth of Brachiaria decumbens. A field experiment was established using a split plot design with three replications. The treatments were, i) three sources of phosphate rock (Riecito and Lizardo of Falcon State and Monte Fresco of Tachira State) at four rates of P₂O₅/ha (0, 50, 100, and 200), ii) one source of high‐solubility P [triple superphosphate (TSP) at the same rates], and iii) three levels of calcium applied as basic slag from the Orinoco Steel Company (0, 300, and 600 kg Ca/ha). A basic fertilization was applied to all plots (217 kg/ha Urea, 50 kg/ha KCl, and 78 kg/ha magnesium sulphate). The pasture species used was Brachiaria decumbens. Pasture and soil samples were taken at 2, 3, 5, 7, 12, 14, 16, 17, 24, 27, and 31 months after planting. The pasture samples were analyzed for dry matter production (DM), and percentage content of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). Soil samples were analyzed for pH, cation exchange capacity (CEC), and available calcium (Ca) and phosphorus (P). The relative agronomic effectiveness (RAE), calculated using the formula: RAE (%) = DM of the rock ‐ DM of the check plot/DM of TSP ‐ DM of check plot × 100 was applied for each harvest time. The best RAE values at each sampling time were obtained with the Monte Fresco phosphate rock at the rate of 200 kg P₂O₅/ha and 600 kg Ca/ha as slag. There was a tendency for the RAE value to improve with each sampling apparently due to the slow release of phosphorus from the phosphate rock and its residual effect. There are also values of RAE that show better dry matter production than the high soluble source of TSP.

Soil available P and Ca increased with phosphate rock and slag application from 5 and 200 mg/kg to 25 and 400 mg/kg, respectively, after 2.5 years of the experiment. Phosphorus uptake changed from 0.1% in the check plot, which is insufficent to supply the P requirement of grazing cattle in the tropics to a value higher than 0.2%, depending on the sampling time. Soil pH increased slightly from 5.2 to 5.6 with phosphate rock, and to 6.2 when basic slags were applied.     

Evaluation of p as a limiting macronutrient in volcanic ash soils of guatemala

Abstract

P status of soils derived from volcanic ash in Guatemala was investigated. Growth chamber and greenhouse studies were conducted with H‐3 hybrid corn (Zea mays). All plants exhibited P deficiency symptoms and yielded less dry matter when they were grown on soils that received only lime at a rate equivalent to 2,240 and 4,480 kg/ha. The P content of plants was low and correlated with P deficiency symptoms. Application of P (336 and 672 kg/ha) under constant liming corrected the P deficiencies and increased dry matter. In comparative studies, plants grown on a highly fertile, non‐volcanic soil showed vigorous growth and yielded high dry matter. Apparently, P was limiting productivity in volcanic ash soils of Guatemala, and due to low exchangeable Al, addition of only lime did not produce beneficial results. The soils responded to P fertilization and they should be supplied large quantities of this macronutrient.     

多菌灵在酸化黑土中迁移性能的抑制

利用自行研制的原状土淋溶柱,研究了多菌灵在蔬菜地酸化黑土中的迁移规律,并通过调控土壤pH值和有机质含量,探讨了抑制多菌灵在黑土中迁移的技术措施。结果表明,添加消石灰,土壤值由5.1上升至6.2,多菌灵淋出量峰值较对照延迟出现,总淋出量较对照处理减少了31.3%;当土壤有机质含量由21.2 g/kg提升至30.7 g/kg时,多菌灵的总淋出量减少了23.7%;当同时添加消石灰和秸秆后,土壤中多菌灵的淋出峰值出现延迟,总淋出量较对照处理减少了46.0%,效果优于消石灰或秸秆单施处理,但混施处理的效果略低于二者单施处理之和。     

Nitrates in soil after long‐term management for dryland grain sorghum and winter wheat

Abstract

The leaching of phosphorus (P), nitrogen (N), and radionuclides (²³²Th, ²²⁶Ra, ²²⁸Ra, and ⁴⁰K) from Joel sands amended with red mud/gypsum (RMG) at 9 rates (0, 2, 4, 8, 16, 32, 64, 128, and 256 t/ha) was measured using columns. Intense leaching conditions (34 mm/day for 12 days) and a high rate of applied P (320 kg/ha as superphosphate) and N (680 kg/ha as ammonium nitrate) were used to simulate extremes of irrigated vegetable production on the Swan Coastal Plain. Addition of the highest rate of RMG (256 t/ha) reduced leaching of fertiliser P and ammonium‐nitrogen (NH₄‐N) by 85% and 50%, respectively, compared with 0 t/ha after 12 days. At 641 RMG/ha P leaching was reduced 50% compared with 0 t/ha. Nitrate‐nitrogen (NO₃‐N) leaching was not affected by addition of RMG.

Reduced leaching of NH₄‐N was attributed to an increase in cation exchange capacity of the soil with the addition of RMG. Bicarbonate‐extractable P in the soil increased with rate of RMG to >50 μg P/g soil at 256 t/ha. This indicates that soil testing of residual P could be used to reduce P inputs to vegetable crops after soils were amended with RMG. This would further reduce the impact of vegetable production on the water systems of the Swan Coastal Plain and extend the period of effectiveness of RMG amended soils. The increase in ²³²Th specific activity in Joel sand amended with RMG was well below statutory limits even at the highest rate. Neither ⁴⁰K nor ²²⁶Ra were detectable in RMG amended sands up to 2561 RMG/ha. There was no evidence of leaching of ²²⁶Ra or ²²⁸Ra at any rate of RMG. These results suggest that the use of RMG amendment on commercial horticultural properties on the Swan Coastal Plain could be feasible.     

Quantitative und qualitative Veränderungen im A-Horizont von Sandböden nach Umwandlung von Dauergrünland in Ackerland

Quantitative and qualitative changes in soil properties of A- horizons of sandy soils caused by conversion of grassland to arable land Changes in physical soil properties and in soil organic matter of the A-horizons due to the conversion of permanent grassland to arable land are quantified and described as a function of time for sandy soils. The study was carried out in an area northeast of Hannover. A decrease of about 100 t/ha C_org (- 57%), 5 – 6 t/ha N_org (- 58%) and 1 t/ha S_t (- 58%) was measured for a period of 2 – 4 years after grassland conversion. Thereby the quality of the soil organic matter remains unchanged (no changes of the C/N ratio and of the distribution of N_org in 5 N-fractions). However, an increase of soil bulk density from 1.0 to 1.3 g/cm³ and a decrease of total pore volume from 0.59 to 0.47 were observed. The fast mineralization of soil organic matter in the A-horizon following the conversion of grassland soils results in a temporary heavily increased nitrate input into the groundwater. Furthermore mineralization and leaching of nitrate and sulfate induces an acidification push in the soil by a proton release in the order of 350 keq/ha during a 2 – 4 years period. However, this proton production is compensated quantitatively by several applications of lime or marl by farmers and by the buffering of bases cations released from mineralized soil organic matter.     

植物吸取修复及钝化处理对后茬水稻镉吸收的影响

采集湖南湘潭县某地镉(Cd)污染酸性农田土壤及其经伴矿景天分别吸取修复两季和三季后的土壤,采用盆栽试验研究了经伴矿景天修复及钝化改良与否对土壤pH、有效态Cd、Zn以及水稻生长和稻米Cd、Zn浓度的影响。结果表明:未改良的处理,随着修复次数的增加,土壤pH显著降低,降低幅度为0.26~0.38个单位;且修复两季、三季土壤CaCl_2提取态Cd浓度较未修复土壤分别降低19.4%、24.0%;修复后土壤种植水稻品种W184,其糙米中Cd浓度显著降低,但依然超标;修复三季土壤种植低积累水稻品种IRA7190,其糙米中Cd由0.47 mg/kg降为0.03 mg/kg。施加钝化剂海泡石和石灰(10 g/kg+1 g/kg)后,修复两季、三季土壤的pH显著升高,较未施钝化剂处理土壤pH分别提高0.95、0.72;土壤CaCl_2提取态Cd浓度分别降低79.8%、79.5%;修复两季、三季土壤上水稻W184糙米的Cd浓度与未施加钝化剂相比,分别降低27.3%、44.4%,均降至国家食品安全限值0.2 mg/kg以下;无论是否添加钝化剂,伴矿景天吸取修复三季的土壤上水稻IRA7190糙米中Cd浓度均仅0.03 mg/kg。     

Seasonal nitrogen dynamics in lowland rice cropping systems in inland valleys of northern Ghana

Farmers in the inland valleys of northern Ghana are challenged with nitrogen (N) deficiency as a major production constraint of rainfed lowland rice (Oryza sativa L.). With extremely low use of external inputs, there is a need to efficiently use the systems' internal resources such as native soil N. Largest soil nitrate‐N losses are expected to occur during the transition between the dry and wet season (DWT) when the soil aeration status changes from aerobic to anaerobic conditions. Technical options avoiding the build‐up of nitrate are expected to reduce N losses and may thus enhance the yield of rice. A field study in the moist savanna zone of Ghana assessed the in situ mineralization of native soil N, the contribution of nitrate to the valley bottom by sub‐surface flow from adjacent slopes, and the effects of crop and land management options during DWT on seasonal soil N_min dynamics and the yield of lowland rice. Large amounts of nitrate accumulated during DWT with a peak of 58 kg ha⁻¹ in lowland soils, of which 32 kg ha⁻¹ were contributed from the adjacent upland slope. Most of this nitrate disappeared at the onset of the wet season, possibly by leaching and denitrification upon soil flooding. While the incorporation of rice straw (temporary immobilization of soil N in the microbial biomass) had little effect on soil N conservation, growing a crop during DWT conserved 22–27 kg of soil N ha⁻¹ in the biomass and Crotalaria juncea supplied an additional 43 kg N ha⁻¹ from biological N₂ fixation. Farmers' practice of bare fallow during DWT resulted in the lowest rice grain yield that increased from 1.3 (2.2) to 3.9 t ha⁻¹ in case of the transition‐season legume. Growing a pre‐rice legume during DWT appears a promising option to manage N and increase lowland rice yields in the inland valleys of northern Ghana.     

Effects of solid phase from pig slurry on soil chemical characteristics,nitrate leaching,composition, and yield of wheat

A two years lysimeter experiment was carried out using wheat plants (Triticum aestivum L. cv. Lotti) on two texturally contrasting soils. The main purpose of this study was to evaluate the influence of increasing applications (5,10, 15,20, and 25 t.ha^‐1) of solid phase (SP) from pig slurry on soil nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na) content, nitrate‐N (NO₃‐N) leaching as well as on wheat composition and yield. As the control, a basic dressing of NPK fertilizer was applied. Results showed that plant growth was stimulated by increasing amounts of SP, yet the additions of 15 to 20 t SP ha^‐1 led to similar effects on yield as that for the control. An accumulation of P on both soils was observed as well as a significant increase on NO₃‐N leaching due to increasing rates of SP added to the soils. The N and P content in wheat plants (straw and grain) increased with increasing rates of applied SP.     

长期稻草还田对紫色水稻土肥力和生产力的影响

通过8年淹水条件下一季中稻的田间定位试验,研究了长期稻草还田以及稻草与不同化肥配合施用对紫色水稻土生产力和土壤肥力的影响。结果表明,稻草与N、P、K化肥配合施用能维持或提高紫色水稻土的生产力和土壤肥力;水稻获得了持续高产,土壤有机质和全氮含量提高,土壤磷的有效性增加,速效钾与试验前基本平衡。纯化肥处理尤其是N、NP、NK处理水稻产量、土壤氮和钾含量逐年降低,不能维持系统生产力和土壤肥力。稻草还田对翌年水稻具有显著的增产作用,8年平均稻草还田处理比对照增产39.5%,稻草的增产作用还随着稻草还田时间的延长而逐年升高。稻草还田携入的钾与化学钾肥具有相同的营养功效,稻草可替代部分化学钾肥。     

Lime and phosphorus interactions on growth and nutrient uptake by upland rice,wheat, common bean,and corn in an Oxisol

Liming and phosphorus (P) applications are common practices for improving crop production in acid soils of the tropical as well as temperate regions. Four greenhouse experiments were conducted on an Oxisol (clayey, kaolinitic, isothermic, Typic Haplustox) to evaluate response of liming (0,2, and 4 g/kg) and P application (0, 50, and 175 mg P/kg) in a factorial combination on growth and nutrient uptake by upland rice (Oryza sativa L.), wheat (Triticum aestivum L.), common bean (Phaseolus vulgaris L.), and corn (Zea mays L.). Phosphorus application significantly (P<0.01) increased dry weight of tops of all the four crop species as well as dry weight of roots of wheat and corn. Liming significantly (P<0.01) improved growth of common bean and corn but had significant negative effects on rice growth. Maximum dry weight of tops of rice and wheat was obtained at 175 mg P/kg without lime. Maximum dry weight of tops in common bean was obtained at 4 g lime/kg with 175 mg P/kg of soil. In all the crops, increasing levels of applied P significantly increased nutrient uptake. With some exceptions, increasing levels of lime tend to reduce uptake of P, zinc (Zn), copper (Cu), manganese (Mn), and iron (Fe) and increase the uptake of calcium (Ca) and magnesium (Mg) in all the crop species. Decrease in potassium (K) uptake, due to high lime, is probably due to antagonistic effects of Ca and Mg and reduced micronutrients uptake is probably due to increased soil pH resulting in decreased availability of these elements to plants. Therefore, in these types of acid soils, one should avoid over liming.     

秸秆还田配施石灰对水田土壤铜、锌、铅、镉活性的影响

秸秆还田是我国培肥地力和增加农田土壤碳固定的重要措施,但进入农田的秸秆存在着活化土壤重金属的风险。为了解不同来源的秸秆对污染水平不同农田土壤重金属活性的影响,采取相应措施防止因秸秆还田对农田土壤重金属的激活,开展了盆栽和田间小区试验研究秸秆还田配施石灰对水田土壤铜、锌、镉、铅活性的影响。盆栽和田间试验在轻度和重度污染2种土壤上同时进行。盆栽试验中施用秸秆包括重污染水稻秸秆、轻污染水稻秸秆和轻污染油菜秸秆3种,石灰用量设对照(0 kg·hm-2)和石灰处理(750 kg·hm-2)2个处理;田间小区试验设对照(不施秸秆和石灰)、秸秆还田及秸秆还田+石灰3个处理。动态观察了试验过程中土壤有效态重金属、重金属形态及水稻籽粒中重金属积累情况。结果表明,试验初期(前20 d)秸秆还田显著增加了水田土壤中水溶性有机碳与水溶性重金属的含量;与对照处理比较,水溶性重金属含量以重度污染土壤增幅较为明显。试验后期(60 d后)秸秆还田对土壤重金属的活性的影响逐渐变得不明显。油菜秸秆还田土壤中水溶性重金属含量低于水稻秸秆还田,重污染水稻秸秆还田土壤中水溶性重金属含量高于低污染水稻秸秆还田。盆栽试验和田间试验的结果都表明,重污染水稻秸秆还田可轻微增加水稻籽粒中镉的积累,但轻度污染水稻秸秆还田与油菜秸秆还田对水稻籽粒镉积累的影响较小;3种秸秆还田对水稻籽粒铅、铜、锌积累的影响不明显。配施石灰可显著降低土壤中水溶性重金属的含量,降低水稻籽粒中重金属的积累。研究认为,在污染农田管理上应控制重污染水稻秸秆还田,在秸秆还田的同时适量配施石灰。     

Short-term effects of raw rice straw and its derived biochar on greenhouse gas emission in five typical soils in China

Abstract

A short-term study was conducted to investigate the greenhouse gas emissions in five typical soils under two crop residue management practices: raw rice straw (Oryza sativa L., cv) and its derived biochar application. Rice straw and its derived biochar (two biochars, produced at 350 and 500°C and referred to as BC350 and BC500, respectively) were incubated with the soils at a 5% (weight/weight) rate and under 70% water holding capacity for 28 d. Incorporation of BC500 into soils reduced carbon dioxide (CO₂) and nitrous oxide (N₂O) emission in all five soils by 4?40% and 62?98%, respectively, compared to the untreated soils, whereas methane (CH₄) emission was elevated by up to about 2 times. Contrary to the biochars, direct return of the straw to soil reduced CH₄ emission by 22?69%, whereas CO₂ increased by 4 to 34 times. For N₂O emission, return of rice straw to soil reduced it by over 80% in two soils, while it increased by up to 14 times in other three soils. When all three greenhouse gases were normalized on the CO₂ basis, the global warming potential in all treatments followed the order of straw > BC350 > control > BC500 in all five soils. The results indicated that turning rice straw into biochar followed by its incorporation into soil was an effective measure for reducing soil greenhouse gas emission, and the effectiveness increased with increasing biochar production temperature, whereas direct return of straw to soil enhanced soil greenhouse gas emissions.     

Effect of organic residue amendment on mineralization of sulfur in flooded rice soils under laboratory conditions

Abstract

This study was undertaken to assess the mineralization of sulfur (S) in laboratory conditions of three rice soils (Joydebpur, Faridpur, and Thakurgaon), receiving the following treatments: 1) control, 2) rice straw (Oryza sativa L.), and 3) pea vine (Pisum sativum L.). The organic residue (25 mg g^‐1) was added and mixed with soil and glass beads (1:1, soil to bead ratio) and placed into a Pyrex leaching tube. The soils were flooded and incubated at 35°C, after which they were leached with deionized water at 1, 2,4, 8, and 12 weeks for analysis of SO₄ and other chemical properties in the leachates. Potentially mineralizable S (S_o) and C (C_o) pools and first‐order rate constants (K_s for S and K_c for C) in soils amended with rice straw and pea vine under flooded conditions were estimated using an exponential equation. The S_o and K_s varied considerably among the soils and types of added organic residues, and their values in rice straw and pea vine ranged from 8.70 to 29.55 and 0.124 to 0.732 mg S kg^‐1 wk^‐1, respectively. Except for the Thakurgaon soil, the S_o and K_s values in Joydebpur and Faridpur soils were higher in the unamended treatments. Higher S_o values in the unamended soils were probably due to less microbial activity to mineralize organic S from organic residues. The results indicate that the amount of SO₄ in flooded soils amended with organic residues are dependent on soil type, nature of organic residues, and time of incubation. The C_o and K_c values under flooded incubation were higher in residue amended soils than in unamended soils. Pea vine treated soils had higher C_o and K_c values than the soils treated with rice straw.     

Effects of repeated straw incorporation on crop fertilizer nitrogen requirements, soil mineral nitrogen and nitrate leaching losses

Abstract. The effects of straw disposal by burning and incorporation on soil and crop nitrogen (N) supply, were investigated on two light textured soils in central (ADAS Gleadthorpe) and eastern England (Morley Research Centre) over the period 1984 to 1995. Nitrogen balance calculations showed that after 11 years of contrasting straw incorporation versus burn treatments, the cumulative N returns in straw were c . 570kg/ha at Gleadthorpe and c . 330 kg/ha at Morley However, these N returns via straw incorporation were not reflected in increased total soil N levels in autumn 1994. There were no differences ( P > 0.05) between straw disposal treatments in autumn soil mineral N supply, readily mineralizable N or organic carbon. Similarly, there were no consistent differences between the treatments in terms of crop yield, crop N uptake or optimum fertilizer N rates. Fertilizer N applications of 200 kg N/ha/y increased topsoil organic carbon from 1.18 to 1.28% and total N content from 0.091 to 0.102% on the loamy sand textured soil at ADAS Gleadthorpe, but not at Morley. Previous fertilizer N applications increased the quantity of nitrate-N leached in drainage water by c . 20 kg/ha at Gleadthorpe and c . 60 kg/ha at Morley overwinter 1994/95, and by 10–20 kg/ha at both sites overwinter 1995/96. There was some indication overwinter 1994/95 that straw incorporation reduced nitrate-N leaching by 10–25 kg/ha, but there were no differences between treatments overwinter 1995/96.