Influence of colored plastic mulch on soil temperature,growth, nutrimental status,and yield of bell pepper under shade house conditions

The aim of this study was to determine if plastic mulch films may have positive effects on bell pepper plants grown under shade house conditions. The experimental design was split-plot, where large plots contained four plastic mulch films (black, aluminum, silver, and white) compared to bare soil and small plots contained two bell pepper cultivars. Plant shoot dry weight was higher in plastic mulch treatments than in bare soil. The net photosynthesis rate in the cultivar SWG-46 exceeded in net photosynthesis with respect to the cultivar SWG-42 in one of three sampling dates. Nutrients in leaf showed a similar behavior in plastic mulch treatments than the control but the total content of nitrogen (N), potassium (K), and sulfur (S) was increased. The total yield was higher in black plastic mulch than in the other plastic mulch colors and lowest in the control.     

Growth,yield and yield components of dry bean as influenced by phosphorus in a tropical acid soil

Phosphorus (P) deficiency is one of the most yield limiting factors for dry bean (Phaseolus vulgaris) production in tropical acid soils. Dry beans are invariably grown as mono-crops or as inter-crops under the perennial tropical crops. Information is limited regarding the influence of phosphorus fertilization on dry bean yield and yield components and P use efficiency in tropical acid soils. A greenhouse experiment was conducted to evaluate the influence of phosphorus fertilization on dry bean growth, yield and yield components and P uptake parameters. Phosphorus rates used were 0, 50, 100, 150, 200, and 250 mg P kg^?1 of soil. Soil used in the experiment was an acidic Inceptisol. Grain yield, shoot dry weight, number of pods, and 100 grain weight were significantly (P < 0.01) increased with phosphorus fertilization. Maximum grain yield, shoot dry matter, number of pods, and 100 grain weight were obtained with the application of 165, 216, 162, and 160 mg P kg^?1 of soil, respectively, as calculated by regression equations. Grain yield was significantly and positively associated with shoot dry weight, number of pods, P concentration in grain and total uptake of P in shoot and grain. Phosphorus use efficiency defined in several ways, decreased with increasing P rates from 50 to 250 mg P kg^?1 of soil. Maximum grain yield was obtained at 82 mg kg^?1 of Mehlich 1 extractable soil P. Results suggest that dry bean yield in Brazilian Inceptisols could be significantly increased with the use of adequate rates of phosphorus fertilization.     

Photosynthesis,growth, and fruit yield of cucumber in response to oxo-degradable plastic mulches

The use of plastic mulch is associated with a higher increase in yield of vegetables. However, at the end of the growing season for each crop, plastic mulching can create environmental pollution that can cause negative impacts on the environment that could be solved by the use of degradable plastics. The aim of this study was to determine the effect of oxo-degradable plastic mulches on soil temperature, growth, gas exchange, and cucumber crop yield. The study was conducted in two locations in the northeast of Mexico during the spring and summer of 2013. The plastic mulch colors with additives were blue, green, and red and each color having 8% and 12% of pigment and 22% and 23% of Titanium dioxide (Rutile). The resultant treatments were compared with the black plastic mulch, which is the standard plastic in the world, and bare soil in a randomized complete block design with three replications in two locations. The mean soil temperature at both locations was statistically higher in black plastic mulch, followed by the oxo-degradable plastics mulches and lowest in the control. Gas exchange was not affected by plastic mulches. SPAD units as the index of chlorophyll content in leaves were very little affected by plastic mulch. Both, commercial and total yield were statistically similar in the oxo-degradable plastic mulches and the black plastic mulch, and lowest in the control. Plastics with higher concentrations of pigment registered higher degradation in both locations. Our results suggest that different plastic mulches impact positively on the yield of cucumber crop. The benefit in yield by the different plastic mulches in the conditions of this study was due to their soil warming ability that results in improved soil temperature, leaf area, and plant dry weight.     

Yield,Nutrient Uptake,and Changes in Soil Chemical Properties as Influenced by Liming and Iron Application in Common Bean in a No-Tillage System

Soil acidity is the principal limiting factor in crop production in Oxisols, and deficiency of micronutrients has increased in recent years because of intensive cropping. A field experiment was conducted over three consecutive years to assess response of common bean (Phaseolus vulgaris L.) to lime and iron (Fe) applications on an Oxisol in a no-tillage system. Changes in selected soil chemical properties in the soil profile (0- to 10- and 10- to 20-cm depths) with liming were also determined. Lime rates used were 0, 12, and 24 Mg ha^–1, and Fe application rates were 0, 50, 100, 150 200, and 400 kg ha^–1. Both lime and Fe were applied as broadcast and incorporated in the soil. Grain yields of common bean were significantly increased with the application of lime. Iron application, however, did not influence bean yield. There were significant changes in soil profile (0- to 10-cm and 10- to 20-cm depths) in pH, calcium (Ca²⁺), magnesium (Mg²⁺), hydrogen + aluminum (H⁺ + Al³⁺), base saturation, acidity saturation, cation exchange capacity (CEC), Ca²⁺ saturation, Mg²⁺ saturation, potassium (K⁺) saturation, and ratios of Ca/Mg, Ca/K, and Mg/K. These soil chemical properties had significant positive association with common bean grain yield. Averaged across two depths and three crops, common bean produced maximum grain yield at pH_w 6.3, Ca²⁺ 3.8 cmol_c kg^–1, Mg²⁺ 1.1 cmol_c kg^–1, 3.5 H⁺ + Al³⁺ cmol_c kg^–1, acidity saturation 41.8%, CEC 7.5 cmol_c kg^–1, base saturation 57.4%, Ca saturation 45.2%, Mg saturation 14.2%, K saturation 9.1%, Ca/Mg ratio 3.1, Ca/K ratio 22.6, and Mg/K ratio 6.7.     

Water-soluble cations in shoot dry weight of common bean and balance of ions in the soil in response to the magnesium application

The increased magnesium (Mg) concentration in vegetables may be reduced due to inter-ionic inhibition caused by the concentration of other water-soluble cations that are mainly associated to low molecular weight organic anions. However, it is not known whether the levels of these compounds in crop residues are modified by increasing the Mg soil application. This study aimed to assess the effects of the Mg application on the contents of water soluble cations [potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), cooper (Cu²⁺), iron (Fe²⁺), manganese (Mn²⁺), and zinc (Zn²⁺)] on common bean plant residues. The experiment was conducted under greenhouse conditions with Ustoxix Quatzipsamment in completely randomized design in 4×5 factorial scheme, with three replicates. The treatments consisted of four rates of Mg [0, 50, 100 and 200 mg kg^?1, source magnesium chloride (MgCl₂)] and five varieties of common bean of the carioca group [BRS Estilo, BRS Ametista, IPR Campos Gerais (CG), IPR Tangará and IAPAR 81]. The Mg rates affected the contents of water soluble Ca²⁺, Mg²⁺, Cu²⁺, Fe²⁺ and Mn²⁺ in the extracts of bean residue. The soluble Mg²⁺ showed a significant correlation with foliar Mg content, indicating the need for further research on the method used to assess nutrient availability in vegetables. The bean varieties showed different responses regarding balance of ions in cation exchange capacity (CEC) and in the Ca/Mg, Ca/K and Mg/K ratios in the soil.     

Yield and yield components of two irrigated red bean cultivars and some soil properties as influenced by wheat residues and nitrogen management

Crop residues are beneficial substances affecting crop production and soil properties. A field experiment was carried out to evaluate the effects of wheat (Triticum aestivum L.) residue rates (0, 25, 50 and 75%) combined with N levels (0, 34.5, 69, 103.5 kg ha^?1) on yield and yield components of two red common bean (Phaseolus vulgaris L.) cultivars and to monitor chemical soil parameters. The experiment was conducted at Research Center, College of Agriculture, Shiraz University, Shiraz, Iran for two years (2008–2009). The experiment was conducted as a split–split plot arranged in a randomized complete blocks design with three replications. The highest seed yield was obtained when 25–50% of residues were incorporated. The highest seed yield, seed weight per plant, 100-seed weight and seed number per pod were obtained with 103.5 kg N ha^?1 with no significant difference to 69 kg N ha^?1. Residue incorporation significantly increased soil organic carbon (SOC) as well as available K and P content. It is possible to sow red common bean as a double cropping by soil incorporation of 25–50% wheat residues with application of 69 kg N ha^?1.     

Nitrogen in plant growth and yield of common bean

The aim of this research was to determine the effect of nitrogen (N) availability on wild Rhizobiumnodulation, plant growth and grain yield of the common bean crop. Experiments were conducted in two growing periods, from 2 March to 3 June 2011 (autumn) and from 21 September to 23 December 2011 (spring), in pots using sand as substrate. Nitrogen concentrations of 5.12 (T1), 7.6 (T2), 10.12 (T3), 12.62 (T4), and 15.12 (T5) mmol L^?1 were supplied by fertigation. In spring, the grain yield, number of grains and shoot growth of both cultivars reduced by effect of N concentration but in the cultivar BRS Valente they reducedonly in autumn. Number of nodules and root growth decreased in both cultivars while N concentration increased in the plant tissues. Nitrogen fertilization is not required to the common bean and its use inhibits nodulation. The increased availability does not enhance plant growth and grain yield.     

The influence of acid soil factors on the growth of snapbeans in major appalachian soils

Abstract

Acid soil limitations to plant growth were assessed In 55 horizons of 14 major Appalachian hill land soils. Aluminum sensitive “Romano” and Al‐tolerant “Dade” snapbeans (Phaseolus vulgaris L.) were grown for 5 weeks in limed and unlimed treatments of the 55 horizons. Shoot and root growth was depressed >20% in unlimed relative to limed treatments in approximately 2/3 of the horizons. Dade snapbeans were generally more tolerant of the acid soil conditions and had higher Ca concentrations in the shoots than Romano snapbeans. However, the sensitive‐tolerant snapbean pair could not consistently be used to identify horizons with soil Al problems. Growth of both snapbeans was generally best in A horizons and worst in E horizons. The E horizons in this study were characterized by low Ca saturation (exchangeable Ca x 100/cation exchange capacity) and high Al saturation (exchangeable Al x 100/cation exchange capacity). Exchangeable Ca, soil Ca saturation and total soil solution Ca were positively correlated (p<0.01) with snapbean root and shoot growth. Soil Al saturation, total soil solution Al and soil solution Al reacting in 15 seconds with 8‐hydroxyquinoline were negatively correlated (p<0.01) with growth. The ratio of Ca/Al in soil solution was more closely related to snapbean growth than the soil solution concentration of any individual element. Soil and soil solution Mn were, in general, not significantly correlated with snapbean growth. Many of the horizons in this study had both Al toxicity and Ca deficiency problems and interaction between Ca and Al affected both snapbean growth and Ca uptake. These findings confirm the importance of considering Ca as well as Al when investigating Al phytotoxicity.     

Micronutrient composition of field‐grown dry bean and wheat inoculated with Azospirillum and Trichoderma

Micronutrient deficiency and malnutrition in humans are severe problems in many developing countries, particularly in areas with calcareous soils. There is almost no information on whether inoculation with plant growth–promoting Azospirillum and/or Trichoderma can help to reduce this problem by increasing the mineral concentration of the seeds. Field experiments were conducted in Tokat (Turkey) in 2001–2002 to determine whether inoculation with Azospirillum brasilense, Trichoderma harzianum, sole or in combination, and/or the application of P fertilizers can enhance micronutrient concentrations of field‐grown bean (Phaseolus vulgaris) and wheat (Triticum aestivum). In beans, Azospirillum inoculation combined with P fertilization significantly (p < 0.05) increased seed concentrations of Mn, Zn, and Cu, from 8.8, 22.6, and 7.0 mg kg^–1 in the control to 10.3, 28.3, and 11.0 mg kg^–1, respectively. Trichoderma inoculation alone significantly (p < 0.05) reduced the concentrations of Fe, Mn, Zn, and Cu and the cumulative plant uptake of Fe and Zn in 45‐day‐old bean plants. However, it significantly (p < 0.05) increased bean‐seed Cu content and accumulation. The double inoculation resulted in significantly (p < 0.05) higher micronutrient concentrations than Trichoderma inoculation alone in 45‐day‐old plants. In contrast to beans, the effects of microbial inoculations were less in wheat. However, dual inoculation significantly (p < 0.05) increased Zn content by 45% and Zn accumulation by 40% above the uninoculated control. Inoculation with plant growth–promoting microorganisms appears to be a promising strategy to combat micronutrient deficiencies.     

Nutrient Uptake and Use Efficiency of Dry Bean in Tropical Lowland Soil

Dry bean is an important source of protein for the population of South America, and yield of this legume is very low in this continent. Knowledge of nutrient uptake and use efficiency of a crop is fundamental to improve yield. A greenhouse experiment was conducted to evaluate growth, nutrient uptake, and use efficiency of dry bean (Phaseolus vulgaris L., cv. BRS Valente) during the growth cycle. Plant samples were collected at 15, 30, 45, 60, 73, and 94 days after sowing. Root dry weight, maximum root length, shoot dry weight, and number of trifoliates were significantly increased in a quadratic fashion with the advancement of plant age. Root dry weight and number of trifoliates had significant positive association with shoot dry weight. Uptake of nutrients in the grain was in the order of nitrogen (N) > potassium (K) > calcium (Ca) > magnesium (Mg) > phosphorus (P) > iron (Fe) > manganese (Mn) > zinc (Zn) > copper (Cu). Hence, it can be concluded the N requirements for bean is greatest and Cu is minimal compared to other essential nutrients for grain yield. Uptake efficiency for root, shoot, and grain production was in the order of P > Mg > Ca > K > N > Cu > Zn > Mn > Fe. The greatest P-use efficiency among macro- and micronutrients can be considered a positive aspect of mineral nutrition of bean, because recovery efficiency of P in acidic Inceptsols is less than 20%.     

Nutrient Uptake in Dry Bean Genotypes

Dry bean is an important legume for human consumption in South America. A greenhouse experiment was conducted to evaluate uptake and use efficiency of macro- and micronutrients by six dry bean genotypes at two P levels (25 and 200 mg kg^?1 soil). Shoot dry weight and grain yield varied significantly among genotypes and significantly increased with increasing phosphorus (P) levels. Grain harvest index (GHI) and 100-grain weight also differ significantly among genotypes and significantly increased with the increasing P levels. Based on grain yield efficiency index (GYEI), genotypes were classified as efficient and inefficient. The most efficient genotype was CNFP 10104, and inefficient genotypes were CNFP 10103 and CNFP 10120. Number of pods per plant and number of seeds per pod increased significantly with the addition of 200 mg P kg^?1 of soil compared to the low level of P (25 mg P kg^?1). Similarly, nitrogen (N), P, calcium (Ca), magnesium (Mg), sulfur (S), zinc (Zn), copper (Cu), and manganese (Mn) concentrations and uptake in the shoot and grain also significantly varied among genotypes. Uptake of macro- and micronutrients was greater under the greater P rate compared to the low P rate. This may be related to greater shoot or grain yield at 200 mg P kg^?1 soil compared to 25 mg P kg^?1 of soil.     

The influence of N concentration and NO3/NH4 ratio on the growth of lima and snap bean and southern field pea seedlings

Abstract

Lima and snap beans and southern field peas were cultured in a modified Hoagland's solution for 14 days with N supplied as Ca(NO₃)₂ and/or (NH₄)₂SO₄ at three N concentrations and five ratios of NO₃ to NH₄. The ratio of NO₃/NH₄, rather than the N concentrations influenced seedling growth of these vegetable legumes. Maximum seedling growth of lima bean was generally obtained with all combinations of NO₃ and NH₄. A preference for 75% NO₃ and 25% NH₄ was observed for snap bean. Southern field pea growth was reduced only when all of the N was supplied as 100% NH₄. Ammonium toxicity symptoms, lesions and severe wilting, developed with snap bean and southern field pea within 14 days when cultured with 100% NH₄. Lima bean, though reduced in growth, exhibited a tolerance to the 100% NH₄ treatment.     

The effectiveness of seed priming and foliar application of zinc- amino acid chelates in comparison with zinc sulfate on yield and grain nutritional quality of common bean

Abstract

The efficacy of seed priming and foliar application of zinc-amino acid chelates including zinc-histidine [Zn(His)₂] and zinc-methionine [Zn(Met)₂] in comparison with zinc sulfate (ZnSO₄) on yield and grain nutritional quality of two common bean cultivars (Phaseolus vulgaris L., cvs Talash and Sadri) was investigated in a severely Zn-deficient calcareous soil (DTPA-Zn: 0.38?mg kg^?1 soil) in a pot experiment. Bean response to Zn application varied depending on the Zn fertilizer, application method and cultivar. In ‘Talash’, seed priming with [Zn(His)₂] and [Zn(Met)₂] led to 24.1 and 11.6% increase in the grain yield of bean in comparison with ZnSO₄ treatment, respectively. In both cultivars, foliar application of [Zn(His)₂] led to significant increase in the grain yield in comparison with ZnSO₄. The highest grain Zn concentration was obtained by seed priming with [Zn(Met)₂] in ‘Sadri’ and [Zn(His)₂] in ‘Talash’, respectively. For Zn-amino acid chelates, seed priming was more effective than foliar application in increasing grain yield and Zn concentration. Foliar application of [Zn(His)₂] and [Zn(Met)₂] in ‘Sadri’ and [Zn(Met)₂] in ‘Talash’ resulted in higher protein content in bean grain as compared with ZnSO₄. In both cultivars, foliar application of [Zn(Met)₂] was the more effective than seed priming to increase grain protein content. The highest water-soluble carbohydrates concentration of grain was obtained by seed priming with [Zn(Met)₂] and [Zn(His)₂] in ‘Sadri’ and ‘Talash’ cultivars, respectively. Therefore, seed priming with [Zn(His)₂] and ZnSO₄ in ‘Sadri’ and [Zn(Met)₂] in ‘Talash’ can effectively be used for improving yield of common bean in Zn-deficient calcareous soils.     

Maize grain production,plant nutrient concentration and soil chemical properties in response to different residue levels from two previous crops

ABSTRACT

The incorporation of previous crop residues in agricultural management benefits soil fertility, crop production, and environment. However, there is no enough information about maximum residue application level without negative effect over next crop yield. To evaluate maize (Zea mays L.) yield under short-time conservation management with incorporation and/or importation of different residue levels, a biannual rotation experiment was conducted in ash volcanic soil in south-central Chile. The experiment consisted of two previous crops, canola (Brassica napus L.) and bean (Phaseolus vulgaris L.), and four levels of residue incorporation (0%, 50%, 100%, and 200% of generated residue; from 0 to 21.4?Mg?ha^?1 for canola and from 0 to 19.0?Mg?ha^?1 for bean). Previous crop species and residue level affected some nutrients concentrations in grain and plant and some soil chemical properties, without effect in maize yield, which averaged 16.6?Mg?ha^?1. Bean residue increased Ca and reduced S in maize plant, increasing soil P, Ca, Mg and K (P?<?0.05). Maize grain Ca content was positively and proportionally affected by canola residue level and negatively and proportionally affected by bean residue level. All canola residue levels increased soil pH and Mg, but the highest level reduced soil S; soil P concentration increased proportionally with bean residue level. The highest bean residue level increased soil S. Different crop and levels of residue did not affect maize yield but did some plant nutrient concentration, and also affected some soil chemical properties.     

适当保水剂施用和覆盖促进旱作马铃薯生长发育和产量提高

为明确保水剂、秸秆覆盖及行间覆膜等抗旱保水措施对旱作马铃薯渗透调节物质、质膜体系等生理特性的影响和对产量的作用效果,以夏波蒂品种马铃薯为材料,设对照、秸秆覆盖、行间覆膜、单施保水剂、秸秆覆盖加施保水剂、行间覆膜加施保水剂6个处理田间试验。结果表明:各处理的马铃薯叶片细胞质膜透性苗期较大,而后呈先降后升趋势;丙二醛、脯氨酸含量随生育期推进呈逐渐增加趋势;可溶性糖含量呈"单峰"曲线变化。行间覆膜加施保水剂、单施保水剂、秸秆覆盖、秸秆覆盖加施保水剂处理较好地缓和了土壤的干旱情况,有效降低了马铃薯叶片中的渗透调节物质和质膜体系。马铃薯生育后期,至淀粉积累期,各处理脯氨酸含量、可溶性糖含量、质膜透性和丙二醛含量变化较为稳定,行间覆膜加施保水剂处理脯氨酸含量、可溶性糖含量、质膜透性和丙二醛含量较对照分别减少15.57%、6.90%、42.79%和17.69%,单施保水剂处理分别减少2.31%、5.17%、10.62%和8.04%,秸秆覆盖处理分别减少28.45%、3.45%、51.63%和25.58%,秸秆覆盖加施保水剂处理分别减少25.14%、12.07%、49.17%和22.58%,降低干旱胁迫程度明显。马铃薯成熟收获期,秸秆覆盖及其加施保水剂处理各土层的土壤含水率变化相对稳定;0～20cm土层加施保水剂处理的土壤含水率相对高于不加保水剂处理。秸秆覆盖、秸秆覆盖加施保水剂、单施保水剂及行间覆膜加施保水剂处理显著增加了马铃薯产量和商品薯率(P<0.05)。总体上,秸秆覆盖处理较有效地缓和了土壤旱情,秸秆覆盖加施保水剂、单施保水剂和行间覆膜加施保水剂处理作用效果也较好,降低了干旱胁迫程度,促进了马铃薯的生长发育、产量提高。     

Soil temperature and moisture content changes with growth and yield of cassava/vegetable intercrops

Field experiments were conducted at the Federal University of Agriculture Abeokuta, Nigeria to evaluate the changes in crop microenvironment, growth and yield performance of intercropping okra, pepper and pumpkin with cassava. The vegetables were planted sole and in mixtures with three cassava cultivars: Idileru, Odongbo and TMS30572. Intercropping reduced weed dry weight and soil temperature but increased soil moisture content, light interception and number of earthworm casts. Cassava/pumpkin intercrop increased soil moisture content, light interception and number of earthworm casts but reduced soil temperatures and weed dry weight compared with cassava/okra and cassava/pepper intercrops. Vegetative characters and fruit yields of okra, pepper and pumpkin were not affected by intercropping. Leaf area index (LAI) of intercropped cassava with pumpkin was reduced but not with okra and pepper. Land equivalent ratio was higher in cassava/okra and cassava/pepper than in cassava/pumpkin intercrop. Cassava/vegetable intercrop is a viable cropping option for high productivity and provision of suitable microenvironment for growth. A short, early-maturing cassava cultivar with a moderate LAI is better adapted in mixture with vegetables.     

Yield,nutritional status and soil fertility cultivated with common bean in response to amino-acids foliar application

Fertilization of common bean (Phaseolus vulgaris) plants with amino-acids (AAs) near the beginning of flowering may increase productivity. This procedure is aimed to avoid waste and increase nutrient use efficiency at the end of the crop cycle, improving the leaf area in the translocation of these nutrients to the common bean. In order to test this hypothesis, a field experiment was conducted on a typic Eutrortox (Oxisol) in randomized block design, with three replicates. Four rates of a solution composed of amino-acids (6.8% glycine, 4.4% proline, 3.3% glutamic acid, 2.7% alanine, 1.9% arginine, 1.7% aspartic acid, 1.3% lysine, 1.3% histidine, and 1.0% leucine) applied 45 days after plant emergence were studied. There was no interaction between years of cultivation × amino-acids. However, the productivity of common bean was significantly influenced by the AAs rates, with the highest seed yield obtained at estimated concentration in 0.0094% of the product in foliar sprays. The increases in the rates resulted in increased foliar nitrogen (N) and zinc (Zn) concentrations and decreased sulfur (S) concentration. The macronutrient uptake was nitrogen>potassium>phosphorus>magnesium > calcium > sulfur (N > K > P > Mg > Ca > S), while for micronutrients it was iron>zinc>boron>copper>manganese (Fe > Zn > B > Cu > Mn). In the soil, the concentrations of organic carbon (C) and available P were negatively affected by the AAs rates.     

Soil carbon sequestration in China through agricultural intensification,and restoration of degraded and desertified ecosystems

The industrial emission of carbon (C) in China in 2000 was about 1 Pg yr⁻¹, which may surpass that of the United States (1ċ84 Pg C) by 2020. China's large land area, similar in size to that of the United States, comprises 124 Mha of cropland, 400 Mha of grazing land and 134 Mha of forestland. Terrestrial C pool of China comprises about 35–60 Pg in the forest and 120–186 Pg in soils. Soil degradation is a major issue affecting 145 Mha by different degradative processes, of which 126 Mha are prone to accelerated soil erosion. Total annual loss by erosion is estimated at 5ċ5 Pg of soil and 15ċ9 Tg of soil organic carbon (SOC). Erosion‐induced emission of C into the atmosphere may be 32–64 Tg yr⁻¹. The SOC pool progressively declined from the 1930s to 1980s in soils of northern China and slightly increased in those of southern China because of change in land use. Management practices that lead to depletion of the SOC stock are cultivation of upland soils, negative nutrient balance in cropland, residue removal, and soil degradation by accelerated soil erosion and salinization and the like. Agricultural practices that enhance the SOC stock include conversion of upland to rice paddies, integrated nutrient management based on liberal use of biosolids and compost, crop rotations that return large quantities of biomass, and conservation‐effective systems. Adoption of recommended management practices can increase SOC concentration in puddled soil, red soil, loess soils, and salt‐affected soils. In addition, soil restoration has a potential to sequester SOC. Total potential of soil C sequestration in China is 105–198 Tg C yr⁻¹ of SOC and 7–138 Tg C yr⁻¹ for soil inorganic carbon (SIC). The accumulative potential of soil C sequestration of 11 Pg at an average rate of 224 Tg yr⁻¹ may be realized by 2050. Soil C sequestration potential can offset about 20 per cent of the annual industrial emissions in China. Copyright © 2002 John Wiley & Sons, Ltd.     

不同培肥措施对土壤物理性状及无机氮的影响

通过田间动态监测,在东北中部黑土区比较了不同培肥措施下0~60 cm土壤三相比、容重、含水量及无机氮的变化。结果表明,黑土的土壤容重在深松后随着玉米生育进程逐渐向初始状态(1.36~1.54 g cm-3)恢复;与常规栽培(T1)相比,深松+深追肥(T3)和深松+深追肥+增施有机肥(T4)可有效降低玉米成熟期时的土壤容重,改善土壤结构,使20~40 cm层次的土壤三相比接近理想值,T4处理下在成熟期(R6)20~30 cm和30~40 cm土层土壤三相比分别为53.4∶25.2∶21.4和50.9∶25.1∶24.0;此外,T4处理下20~40 cm土壤容重至成熟期时仍保持在1.16~1.29 g cm-3。深松促进了硝态氮的下移,优化了土壤中氮的分配;在开花后,T4处理下20~40 cm土层中硝态氮含量占总含量的31.1%~37.5%,有效的满足了生育后期根系对养分的需求;T4处理下20~50 cm土壤含水量显著提高,较T1处理下平均提高18.0%。研究表明,深松+深追肥+增施有机肥可以改善土壤物理环境,尤其是在20~40 cm,并能显著提升土壤水养库容能力,从而促进养分吸收,提高玉米产量。     

Stress Induced by Heavy Metals Cd and Pb in Bean (Phaseolus Vulgaris L.) Grown in Nutrient Solution

The increasing number of cases of soil contamination by heavy metals has affected crop yields, and represents an imminent risk to food. Some of these contaminants, such as cadmium (Cd) and lead (Pb), are very similar to micronutrients, and thus can be absorbed by plants. This study evaluated the translocation of increasing amounts of cadmium and lead and the effects of these metals in the production of beans. Bean plants were grown in nutrient solution Clark and subjected to increasing levels of Cd (from 0 to 0.5 mg L^?1) and Pb (from 0 to 10 mg L^?1). Cadmium concentration of 0.1 mg L^?1 translocated 39.8% to the shoot, and dry matter production was reduced by 45% in shoots and 80% in roots, compared to the control treatment. Lead showed impaired movement in the plant, however the concentration of 1.0 mg L^?1 was observed in 5.7% of metal translocation to the leaves. The concentration of 10 mg L^?1 Pb reduced dry matter production of roots and shoots in 83% and 76%, respectively, compared to the control treatment.