Manure Application and Cannabis Cultivation Influence on Speciation of Lead and Cadmium by Selective Sequential Extraction

The contamination of agricultural soils by heavy metals is a worldwide problem. Degradation of organic matter (OM) from organic amendments used in the remediation of metal-contaminated soils leads to changes in soil chemical properties shortly after their addition, which may affect the soil metal distribution. The effects of four differing organic amendments on chemical forms of Pb and Cd in a contaminated soil were investigated in a pot experiment of control unamended soil and soils amended with dry cow and poultry manures (20 g CM or PM kg^?1 soil), and cow and poultry manure extracts (2 g CME or PME kg^?1 soil) cultured with cannabis sativa. After eight weeks, a sequential extraction scheme was used to fractionate soil Pb and Cd into soluble-exchangeable (Sol-Exch), organic matter associated (AOM), and carbonates associated (ACar) forms. The addition of animal manures and their extracts increased the DTPA-extractable Pb and Cd in soil significantly. Soil Pb and Cd in Sol-Exch fraction were increased by manure applications. Both Pb and Cd in AOM fraction were increased by application of manures and their extracts. This increase was more obvious for Pb in application of cow and poultry manure extracts. The ACar chemical forms of Pb and Cd were also increased by application of manures and their extracts. The increases of Pb and Cd in Acar fraction was noticeable in soils treated with cow manure. Soil cultivation with cannabis sativa increased available, Sol-Exch, and AOM chemical forms of Pb in soil significantly compared to control soil. However, soil Pb and Cd in ACar fraction were decreased significantly by cannabis cultivation. The effect of cannabis cultivation on all of the Cd chemical forms (except on Sol-Exch) was similar to the results of Pb chemical forms. Plant cultivation had no significant effect on Cd in Sol-Exch chemical form.     

Heavy metals fractionation and organic matter mineralisation in contaminated calcareous soil amended with organic materials

Degradation of organic matter (OM) from organic amendments used in the remediation of metal contaminated soils leads to changes in soil chemical properties shortly after their addition, which may affect the soil metal distribution. The effects of two differing organic amendments on OM mineralisation and fractionation of heavy metals in a contaminated soil were investigated in an incubation experiment. The treatments were: control unamended soil, soil amended with fresh cow manure, and soil amended with a compost having a high maturity degree. The soil used was characteristic of the mining area at La Unión (Murcia, Spain) with 28% CaCO(3) and sandy-loam texture (pH 7.7; 2602 mg kg(-1)Zn; 1572 mg kg(-1)Pb). Manure and compost C-mineralisation after 56 days (24% and 3.8%, respectively) were below values reported previously for uncontaminated soils. Both amendments favoured Zn and Pb fixation, particularly the manure. Mn solubility increased at the beginning of the experiment due to a pH effect, and only Cu solubility increased through organic matter chelation in both amended soils.     

On the tropical soils; The influence of organic matter (OM) on phosphate bioavailability

Application of organic manure (OM) and crop residues in agricultural soils can potentially influence positively or negatively the availability of soil phosphorus (P) through soil mineralization, sorption, or desorption of soil-bound P. Traditionally, the addition of OM can reduce the capacity of the soil colloids to adsorb P, thus increasing the release of P in soil solution, but also added OM can increase the adsorption site and increase the fixation or sorption of P to soil colloids, thus reducing the availability of P in soil solution and loss to the environment. The highly weathered tropical soils (HWTS) are susceptible to P insufficiency because HWTS have high P adsorption and fixation; this is mainly due to high concentration of P adsorbent. The main P adsorbents in HWTS include Al, Fe, Ca, and clay minerals, which are principally the same binding or adsorbent for OM compounds, but in excess, are toxic (Al and Fe) to crops. Thus, the presence of OM in HWTS can compromise the adsorption and availability of P in agricultural soils following phosphatic fertilizer applications. In this study, the influence of OM on P adsorption and availability was characterized to have a clear understanding of how OM influences P availability in agricultural soils, especially in highly weathered tropical soil. It is clearly outlined that the application of OM and crop residues can positively or negatively influence the availability of P in agricultural soils for plant uptake and dictate the P that is available for loss to the environment. Thus, the addition of organic matter as a strategy to increase P bioavailability for plant uptake must be treated with care because their contribution is not strait forward to be positive in many agricultural soils.     

Recovery of Soil Ammonia Oxidation After Long-Term Zinc Exposure Is Not Related to the Richness of the Bacterial Nitrifying Community

A soil sterilization–reinoculation approach was used to manipulate soil microbial diversity and to assess the effect of the diversity of the ammonia-oxidizing bacteria (AOB) on the recovery of the nitrifying community to metal stress (zinc). Gamma-irradiated soil was inoculated with 13 different combinations of up to 22 different soils collected worldwide to create varying degrees of AOB diversity. Two months after inoculation, AOB amoA DGGE based diversity (weighted richness) varied more than 10-fold among the 13 treatments, the largest value observed where the number of inocula had been largest. Subsequently, the 13 treatments were either or not amended with ZnCl₂. Initially, Zn amendment completely inhibited nitrification. After 6 months of Zn exposure, recovery of the potential nitrification activity in the Zn amended soils ranged from <10 % to >100 % of the potential nitrification activity in the corresponding non-amended soils. This recovery was neither related to DGGE-based indices of AOB diversity nor to the AOB abundance assessed 2 months after inoculation (p?>?0.05). However, recovery was significantly related (r?=?0.75) to the potential nitrification rate before Zn amendment and only weakly to the number of soil inocula used in the treatments (r?=?0.46). The lack of clear effects of AOB diversity on recovery may be related to an inherently sufficient diversity and functional redundancy of AOB communities in soil. Our data indicate that potential microbial activity can be a significant factor in recovery.     

The effects of mineral fertilizer and organic manure on soil microbial community and diversity

The effects of mineral fertilizer (NPK) and organic manure on phospholipid fatty acid profiles and microbial functional diversity were investigated in a long-term (21-year) fertilizer experiment. The experiment included nine treatments: organic manure (OM), organic manure plus fertilizer NPK (OM + NPK), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer N (N), fertilizer P (P), fertilizer K (K), and the control (CK, without fertilization). The original soil was extremely eroded, characterized by low pH and deficiencies of nutrients, particularly N and P. The application of OM and OM + NPK greatly increased crop yields, soil pH, organic C, total N, P and K, available N, P and K content. Crop yields, soil pH, organic C, total N and available N were also clearly increased by the application of mineral NPK fertilizer. The amounts of total PLFAs, bacterial, Gram-negative and actinobacterial PLFAs were highest in the OM + NPK treatment, followed by the OM treatment, whilst least in the N treatment. The amounts of Gram-positive and anaerobic PLFAs were highest in the OM treatment whilst least in the P treatment and the control, respectively. The amounts of aerobic and fungal PLFAs were highest in the NPK treatment whilst least in the N and P treatment, respectively. The average well color development (AWCD) was significantly increased by the application of OM and OM + NPK, and the functional diversity indices including Shannon index (H ^′ ), Simpson index (D) and McIntosh index (U) were also significantly increased by the application of OM and OM + NPK. Principal component analysis (PCA) of PLFA profiles and C source utilization patterns were used to describe changes in microbial biomass and metabolic fingerprints from nine fertilizer treatments. The PLFA profiles from OM, OM + NPK, NP and NPK were significantly different from that of CK, N, P, K and NK, and C source utilization patterns from OM and OM + NPK were clearly different from organic manure deficient treatments (CK, N, P, K, NP, NK 6 and NPK). Stepwise multiple regression analysis showed that total N, available P and soil pH significantly affected PLFA profiles and microbial functional diversity. Our results could provide a better understanding of the importance of organic manure plus balanced fertilization with N, P and K in promoting the soil microbial biomass, activity and diversity and thus enhancing crop growth and production.     

A negative influence of manure on calcareous soils

Summary On a soil rich in CaCO₃ in a semiaride climate in Algeria a hard soil layer, impermeable for plant roots, was formed in a depth of 20–40 cm after farmyard manure application and irrigation. To find the reason soil samples of this field were taken and leaching experiments were carried out in the laboratory, with the result that much more Caions and HCO₃-ions were leached out of the soils with farmyard manure application than from the soils without manure. Probably the high amount of CO₂, being liberated by the organic matter, and the irrigation water dissolved the CaCO₃ in the soil, and the formed Ca- and HCO₃-ions followed the movement of water in the soil. Where the Ca(HCO₃)₂ reached soil layers with a less amount of CO₂, CaCO₃ precipitated and formed the hard soil layer. In order to avoid the formation of such calcareous crusts on irrigated, limy soils in a dry climate it is recommended to fertilize rather often small quantities instead of rarely big quantities of farmyard manure.     

Responses of maize grain yield to changes in acid soil characteristics after soil amendments

An experiment was conducted from 1997 to 2000 on an acid soil in Cameroon to assess the effectiveness of cultivating acid tolerant maize (Zea mays L.) cultivar and the use of organic and inorganic fertilizers as options for the management of soil acidity. The factors investigated were: phosphorus (0 and 60 kg ha^?1), dolomitic lime (0 and 2 t ha^?1), organic manure (no manure, 4 t ha^?1 poultry manure, and 4 t ha^?1 of leaves of Senna spectabilis), and maize cultivars (ATP-SR-Y – an acid soil-tolerant, and Tuxpeño sequia – an acid susceptible). On acid soil, maize grain yield of ATP-SR-Y was 61% higher than the grain yield of Tuxpeño sequia. Continuous maize cultivation on acid soil further increased soil acidity, which was manifested by a decrease in pH (0.23 unit), exchangeable Ca (31%) and Mg (36%) and by an increase in exchangeable Al (20%). Yearly application of 60 kg ha^?1 of P for 3 years increased soil acidity through increases in exchangeable Al (8%) and H (16%) and a decrease in exchangeable Ca (30%), Mg (11%) and pH (0.07 unit). Lime application increased grain yield of the tolerant (82%) and susceptible (208%) cultivars. The grain yield increases were associated with a mean decrease of 43% in exchangeable Al, and 51% in H, a mean increase of 0.27 unit in pH, 5% in CEC, 154% in exchangeable Ca, and 481% in Mg contents of the soil. Poultry manure was more efficient than leaves of Senna producing 38% higher grain yield. This yield was associated with increases in pH, Ca, Mg and P, and a decrease in Al. The highest mean grain yields were obtained with lime added to poultry manure (4.70 t ha^?1) or leaves of Senna (4.72 t ha^?1). Grain yield increase was more related to the decrease in exchangeable Al (r = ?0.86 to ?0.95, P<0.01) and increase in Ca (r = 0.78–0.94, P<0.01), than to pH (r = ?0.57 (non-significant) to ?0.58 (P<0.05)). Exchangeable Al was the main factor determining pH (r = ?0.88 to ?0.92, P<0.01). The yield advantage of the acid tolerant cultivar was evident even after correcting for soil acidity. Acid soil-tolerant cultivars are capable of bringing unproductive acid soils into cultivation on the short run. The integration of soil amendments together with acid soil-tolerant cultivar offers a sustainable and comprehensive strategy for the management of acid soils in the tropics.     

Diversity of cultivable Azotobacter in the semi-arid alfisol receiving long-term organic and inorganic nutrient amendments

Monitoring the biological processes and microbial diversity is essential for sustaining the soil health for long-term productivity. In the present study, the impact of long-term nutrient management systems on changes in Azotobacter diversity of Indian semi-arid alfisol was assessed. Three soils, i.e., unfertilized control, soils amended with organic manures (OM), and with inorganic chemical fertilizers (IC) from century-old experimental fields were evaluated for Azotobacter diversity by Amplified Ribosomal DNA Restriction Analysis (ARDRA). Bray–Curtis’s similarity index of the ARDRA data of the isolates was analyzed by non-metric multi-dimensional scaling and hierarchical cluster analysis. The results revealed that the long-term organically managed soil recorded significantly higher soil organic carbon, microbial biomass carbon, and total culturable bacterial counts, whereas the chemical fertilized and control soils remained unaffected. Though the Azotobacter population was significantly higher in OM soil than IC and control soils, the genetic diversity was unaffected due to long-term addition of either organic manures or inorganic chemical fertilizers. This result implies the importance of continuous addition of organic manures and also the optimal use of inorganic chemical fertilizers without disturbing the biological properties of the soil.     

Influence of fertilizers on nitrogen mineralization and utilization in the rhizosphere of wheat

Plant roots and microorganisms play an important role in the soil N cycle and plant N nutrition through the release of extracellular enzymes. In the present greenhouse pot experiment, wheat (Triticum aestivum) seedlings were grown in a fluvo-aquic soil (Udifluvent) to investigate N mineralization and utilization in the rhizosphere of wheat. The soil received chemical fertilizer (¹⁵N-labeled urea), chemical fertilizer plus manure (common urea + ¹⁵N-labeled swine manure) or no N. Plant roots were separated from the soil with a nylon cloth, and 1-mm increments of soil moving laterally away from roots were analyzed for N, microbial C, and the activities of invertase, urease and protease. Chemical fertilizer plus manure promoted wheat growth and N absorption significantly compared with chemical fertilizer. ¹⁵N from both chemical fertilizer and swine manure accumulated significantly in the rhizosphere soil within 5 mm of the roots. Fertilized N could thus move easily laterally towards roots and there was no indication that movement through the soil limited plant N supply. A large proportion of fertilizer N was lost from the soil during the wheat growing period, and N utilization efficiency was 24% for chemical fertilizer and 30% for swine manure. In addition, faster rates of N mineralization, larger amounts of microbial C, and increased activities of invertase, urease and protease occurred in the rhizosphere compared with other parts of the soil. There was a significant correlation between microbial C and N mineralization rate (r?=?0.968, P?<?0.01) in the whole soil. Microbial C also showed significant positive correlations with activities of invertase (r?=?0.892, P?<?0.01) and protease (r?=?0.933, P?<?0.01). Further study showed that adding manure into soil increased microbial C and the activities of invertase and protease; adding urea stimulated urease activity in the same soil. Changes in soil enzyme activities in response to N fertilizers could be considered indicators for different fertilizer managements.     

A farm-scale investigation of the organic matter composition and soil chemistry of Andisols as influenced by land use and management

Andisols are characterised by having abundant reactive Al in the form of short-range ordered (SRO) Al constituents and organo-Al complexes, which facilitates the accumulation of soil organic matter (OM). However, recent studies of New Zealand pastoral systems have reported loss of carbon (C) from Andisols when under intense management. This study compares the organic and inorganic chemistry of Andisols on two adjacent pasture sites under different pastoral management regimes (Paddock 2 being more intensively managed than Paddock 1), as well as under a nearby pine stand (Forest). Mean soil pH-H₂O in Forest (5.3) was significantly lower (P?<?0.05) than that in Paddock 1 (5.7), which itself was significantly lower (P?<?0.05) than in Paddock 2 (6.1). Soil C concentrations were significantly higher (P?<?0.05) in the soils under pasture than under pine (63.8 g C/kg), and C in Paddock 1 (98.1 g C/kg) was significantly higher (P?<?0.05) than in Paddock 2 (84.1 g C/kg). The ratio of Al in organo-Al complexes (as estimated with sodium pyrophosphate) to the sum of Al in both SRO and organo-Al complexes (Al_p/Al_o) was significantly smaller (P?<?0.05) as the alkalinity of the soils increased (0.38, 0.23, 0.16 for Forest, Paddock 1 and Paddock 2, respectively). At the molecular level, soils under Forest had a larger relative contribution of degraded products of plant polysaccharides than those under pasture, while these had a larger contribution of fresh (e.g. cellulose and cutan/suberan aliphatic structures) and N-rich OM (e.g., microbial fingerprints, denoting a high microbial activity). Dissolved organic C content in the rhizosphere of pasture species was similar between paddocks, but Paddock 2 had a significantly (P?<?0.05) greater contribution of organic acids of MW?<?500 Da and higher pH (6.8 vs. 6.2). The results (1) confirm the common enrichment in organic C of New Zealand top soils under pasture compared to those under pine, and (2) reveal that the changes in the soil chemistry associated with pasture management may weaken the ability of these soils to preserve OM.     

Sorption and Desorption of Napropamide in Sandy Soil Amended with Chicken Dung and Palm Oil Mill Effluent

Beach Ridges Interspersed with Swales (BRIS) is a sandy soil and in Malaysia it is found exclusively in the east coast of Peninsular Malaysia. It is a marginal soil because of its low nutrient and water-holding capacity. However, with proper management and organic matter amendments some areas with BRIS soil are cultivated. Napropamide is a selective herbicide widely used to control weeds in BRIS soil. No previous studies have been reported on the effects of organic matter amendments on napropamide sorption in BRIS soil. This study was conducted to determine sorption and desorption of napropamide in BRIS soil amended with chicken dung (CD) and palm oil mill effluent (POME) at 0, 20, 40, and 80 Mg ha^?1. Potential interaction of dissolved organic carbon (DOC) with napropamide and their competition for sorption sites were also determined. Sorption isotherm data were fitted to the log-transformed Freundlich's equation. Sorption of napropamide was higher in soils amended with CD and POME as compared to non-amended soil. At the same rates of application, sorption was higher in soil amended with CD than POME. The Freundlich's coefficient (K_f) values were 0.22, 3.96, and 41.6 for nonamended soil, soil amended with 80 Mg ha^?1 POME, and soil amended with 80 Mg ha^?1 CD, respectively. Desorption of napropamide showed positive hysteresis and the hysteresis were greater with higher rates of CD and POME. There was no association between napropamide and DOC extracted from BRIS soil amended with either CD or POME and also there were no competitions between napropamide and DOC extracted from either CD or POME for sorption sites of the soil samples.     

Long-term manuring and fertilization effects on soil organic carbon pools under a wheat–maize cropping system in North China Plain

The effects of organic manure and chemical fertilizer on total soil organic carbon (C _T), water-soluble organic C (C _WS), microbial biomass C (C _MB), labile C (C _L), C mineralization, C storage and sequestration, and the role of carbon management index (CMI) in soil quality evaluation were studied under a wheat–maize cropping system in a long-term experiment, which was established in 1989 in the North China Plain. The experiment included seven treatments: (1) OM: application of organic manure; (2) 1/2OMN: application of half organic manure plus chemical fertilizer NPK; (3) NPK: balanced application of chemical fertilizer NPK; (4) NP: application of chemical fertilizer NP; (5) PK: application of chemical fertilizer PK; (6) NK: application of chemical fertilizer NK; and (7) CK: unfertilized control. Application of organic manure (OM and 1/2OMN) was more effective for increasing C _T, C _WS, C _MB, C _L, C mineralization, and CMI, as compared with application of chemical fertilizer alone. For the chemical fertilizer treatments, balanced application of NPK (treatment 3) showed higher C _T, C _WS, C _MB, C _L, C mineralization, and CMI than the unbalanced use of fertilizers (treatments 4, 5, and 6). The C storage in the OM and 1/2OMN treatments were increased by 58.0% and 26.6%, respectively, over the NPK treatment, which had 5.9–25.4% more C storage than unbalanced use of fertilizers. The contents of C _WS, C _MB, and C _L in organic manure treatments (treatments 1 and 2) were increased by 139.7–260.5%, 136.7–225.7%, and 150.0–240.5%, respectively, as compared to the CK treatment. The CMI was found to be a useful index to assess the changes of soil quality induced by soil management practices due to its significant correlation with soil bulk density and C fractions. The OM and 1/2OMN treatments were not a feasible option for farmers, but a feasible option for sequestering soil carbon, especially for the OM treatment. The NPK treatment was important for increasing crop yields, organic material inputs, and soil C fractions, so it could increase the sustainability of cropping system in the North China Plain.     

Measuring carbon dynamics in field soils using soil spectral reflectance: prediction of maize root density, soil organic carbon and nitrogen content

This paper reports the development of a proximal sensing technique used to predict maize root density, soil carbon (C) and nitrogen (N) content from the visible and near-infrared (Vis-NIR) spectral reflectance of soil cores. Eighteen soil cores (0?C60?cm depth with a 4.6?cm diameter) were collected from two sites within a field of 90-day-old maize silage; Kairanga silt loam and Kairanga fine sandy loam (Gley Soils). At each site, three replicate soil cores were taken at 0, 15 and 30?cm distance from the row of maize plants (rows were 60?cm apart). Each soil core was sectioned at 5 depths (7.5, 15, 30, 45, and 60?cm) and soil reflectance spectra were acquired from the freshly cut surface at each depth. A 1.5?cm soil slice was taken at each surface to obtain root mass and total soil C and N reference (measured) data. Root densities decreased with depth and distance from plant and were lower in the silt loam, which had the higher total C and N contents. Calibration models, developed using partial least squares regression (PLSR) between the first derivative of soil reflectance and the reference data, were able to predict with moderate accuracy the soil profile root density (r ²?=?0.75; ratio of prediction to deviation [RPD]?=?2.03; root mean square error of cross-validation [RMSECV]?=?1.68?mg/cm³), soil% C (r ²?=?0.86; RPD?=?2.66; RMSECV?=?0.48%) and soil% N (r ²?=?0.81; RPD?=?2.32; RMSECV?=?0.05%) distribution patterns. The important wavelengths chosen by the PLSR model to predict root density were different to those chosen to predict soil C or N. In addition, predicted root densities were not strongly autocorrelated to soil C (r?=?0.60) or N (r?=?0.53) values, indicating that root density can be predicted independently from soil C. This research has identified a potential method for assessing root densities in field soils enabling study of their role in soil organic matter synthesis.     

Leaching of Zinc,Cadmium, and Lead in a Sandy Soil Due to Application of Poultry Litter

Dissolved organic matter in poultry litter could contribute organic ligands to form complexes with heavy metals in soil. The soluble complexes with heavy metals can be transported downward and possibly deteriorate groundwater quality. To better understand metal mobilization by soluble organic ligands in poultry litter, soil columns were employed to investigate the movement of zinc (Zn), cadmium (Cd), and lead (Pb). Uncontaminated soil was amended with Zn, Cd, and Pb at rates of 400, 8, and 200 mg kg ^{? 1} soil, respectively. Glass tubes, 4.9-cm-diameter and 40-cm-long, were packed with either natural or metal-amended soil. The resulting 20-cm-long column of soils had bulk density of about 1.58 g cm ^{? 3} . Columns repacked with natural or amended soil were leached with distilled water, 0.01 M EDTA, 0.01 M CaCl ₂ , or poultry litter extract (PLE) solutions. Low amounts of Zn, Cd, and Pb were leached from natural soil with the solutions. Leaching of Zn, Cd, or Pb was negligible with distilled water. In the metal-amended soil, EDTA solubilized more Zn, Cd, and Pb than CaCl ₂ and PLE. The breakthrough curves of Zn and Pb in the PLE and CaCl ₂ were similar, indicating they have similar ability to displace Zn and Pb from soils. Compared with Zn and Cd the PLE had a small ability to solubilize Pb from metal-amended soil. Thus, the application of poultry litter on metal-contaminated soils might enhance the mobility of Zn and Cd.     

Biochar co-compost improves nitrogen retention and reduces carbon emissions in a winter wheat cropping system

Organic amendments, such as compost and biochar, mitigate the environmental burdens associated with wasting organic resources and close nutrient loops by capturing, transforming, and resupplying nutrients to soils. While compost or biochar application to soil can enhance an agroecosystem's capacity to store carbon and produce food, there have been few field studies investigating the agroecological impacts of amending soil with biochar co-compost, produced through the composting of nitrogen-rich organic material, such as manure, with carbon-rich biochar. Here, we examine the impact of biochar co-compost on soil properties and processes by conducting a field study in which we compare the environmental and agronomic impacts associated with the amendment of either dairy manure co-composted with biochar, dairy manure compost, or biochar to soils in a winter wheat cropping system. Organic amendments were applied at equivalent C rates (8 Mg C ha⁻¹). We found that all three treatments significantly increased soil water holding capacity and total plant biomass relative to the no-amendment control. Soils amended with biochar or biochar co-compost resulted in significantly less greenhouse gas emissions than the compost or control soils. Biochar co-compost also resulted in a significant reduction in nutrient leaching relative to the application of biochar alone or compost alone. Our results suggest that biochar co-composting could optimize organic resource recycling for climate change mitigation and agricultural productivity while minimizing nutrient losses from agroecosystems.     

有机物料与锌肥配施对石灰性土壤锌有效性及形态转化的影响

采用尼龙网袋田间填埋培养法探究了外源施锌条件下石灰性土壤Zn有效性及形态转化对不同有机物料(作物秸秆、生物菌肥、黄腐酸和腐熟鸡粪)的响应.结果表明:与对照相比,Zn肥单施和与有机物料配施均显著提高了土壤全Zn含量(7.2%~13.8%)和DTPA-Zn含量(2.1~2.8倍).在施Zn条件下,有机物料对土壤全Zn和DTPA-Zn的贡献量表现为腐熟鸡粪>生物菌肥>玉米秸秆>黄腐酸,但外源锌的DTPA-Zn转化率以添加秸秆和生物菌肥处理最高.与单施Zn肥相比,有机物料与Zn配施处理显著提高了土壤有机质含量,促进了松结有机态Zn的形成,进而提高了土壤Zn转移因子,降低了Zn分配指数.不同物料与Zn肥配施土壤Zn有效性及形态转化之间存在差异,这可能与有机物料自身性质如腐熟度和含Zn量有关.尽管秸秆与Zn配施对DTPA-Zn含量的提升效果不及生物菌肥或腐熟鸡粪与Zn配施,但综合考虑环境和经济效益,其仍是改善缺锌石灰性土壤Zn有效性的最佳选择.     

Vesicular-arbuscular mycorrhizal effectiveness in an acid soil amended with fresh organic matter

A greenhouse investigation was undertaken to determine the influence of fresh organic matter on the formation and functioning of vesicular-arbuscular mycorrhizal symbiosis in Leucaena leucocephala grown in an acid aluminum-rich ultisol. In soil not amended with fresh organic matter or lime, plants failed to grow. Mycorrhizal infection level, mycorrhizal effectiveness measured in terms of pinnule P content of L. leucocephala leaves and dry matter yield of the legume increased with increase in fresh organic matter. Although VAM colonization level and dry matter yield of L. leucocephala were significantly higher if the test soil was limed (7.2 cmole OH^–) than if amended with fresh organic matter, the latter was as effective as lime in off-setting the detrimental effect of aluminum on mycorrhizal effectiveness. The lower mycorrhizal colonization level and the lower dry matter yield noted in the soil treated with fresh organic matter appears to be related to the inadequacy of Ca in the soil amended with fresh organic matter. These observations are supported by the low calcium status of soil and plant tissues in the absence of lime. It is concluded that while fresh organic matter, in appropriate amounts, could protect sensitive plants and VAM symbiosis against Al toxicity in acid soils, maximum mycorrhizal inoculation effects are not likely to be attained unless the soils are also amended with Ca.Contribution from Hawaii Institute of Tropical Agriculture and Human Resources Journal Series No 3740.     

Nitrogen mineralization in a green manure-amended soil as influenced by cropping history and subsequent crop

A greenhouse experiment was conducted to determine the influence of cropping variables on nitrogen dynamics in a soil amended with green manure. Surface soil from various long-term spring wheat rotations was amended with¹⁵N-labelled legume green manure (Lathyrus tingitanus) and subsequently cropped (canola [Brassica napus] and spring wheat [Triticum aestivum]) or incubated without a crop for 56 days in a greenhouse. Nitrogen mineralization from both the indigenous soil N and from green manure was suppressed in cropped soil. Net N mineralization in the uncropped and cropped treatments averaged 73 and 43 mg kg⁻¹, respectively. This difference was attributed, in part, to enhanced biological immobilization in the rhizosphere. Previous cropping practices also had significant effect on N mineralization, largely by their influence on indigenous organic matter quality. These observations suggest that short-term N mineralization is favored by fallowing soil after green manure application whereas N retention in organic matter is favored by immediate cropping. Contribution 3878873     

Effect of Different Fertilizer Application on the Soil Fertility of Paddy Soils in Red Soil Region of Southern China

Appropriate fertilizer application is an important management practice to improve soil fertility and quality in the red soil regions of China. In the present study, we examined the effects of five fertilization treatments [these were: no fertilizer (CK), rice straw return (SR), chemical fertilizer (NPK), organic manure (OM) and green manure (GM)] on soil pH, soil organic carbon (SOC), total nitrogen (TN), C/N ratio and available nutrients (AN, AP and AK) contents in the plowed layer (0–20 cm) of paddy soil from 1998 to 2009 in Jiangxi Province, southern China. Results showed that the soil pH was the lowest with an average of 5.33 units in CK and was significantly higher in NPK (5.89 units) and OM (5.63 units) treatments (P<0.05). The application of fertilizers have remarkably improved SOC and TN values compared with the CK, Specifically, the OM treatment resulted in the highest SOC and TN concentrations (72.5% and 51.2% higher than CK) and NPK treatment increased the SOC and TN contents by 22.0% and 17.8% compared with CK. The average amounts of C/N ratio ranged from 9.66 to 10.98 in different treatments, and reached the highest in OM treatment (P<0.05). During the experimental period, the average AN and AP contents were highest in OM treatment (about 1.6 and 29.6 times of that in the CK, respectively) and second highest in NPK treatment (about 1.2 and 20.3 times of that in the CK). Unlike AN and AP, the highest value of AK content was observed in NPK treatments with 38.10 mg·kg⁻¹. Thus, these indicated that organic manure should be recommended to improve soil fertility in this region and K fertilizer should be simultaneously applied considering the soil K contents. Considering the long-term fertilizer efficiency, our results also suggest that annual straw returning application could improve soil fertility in this trial region.     

旱地施有机肥对土壤有机质和水稳性团聚体的影响

通过渭北旱塬2007-2010年田间定位试验,研究了有机肥不同施用量(低量7500 kg·hm^-2、中量15000 kg·hm^-2、高量22500 kg·hm^-2)对连作玉米地土壤有机质、团聚体各层粒径分布和稳定性的影响.结果表明：0～20 cm土层,高量有机肥处理土壤有机质含量较低量有机肥处理提高4.1%～4.6%,高、中量有机肥处理较对照提高4.6%～11.2%,低量有机肥处理在施肥第4年（2010年）较CK提高4.7%～6.3%.0～30 cm土层,所有有机肥处理>5 mm水稳性团聚体的增幅最大,其含量随有机肥用量的增加而显著升高;有机肥处理显著提高了土壤>0.25 mm水稳性团聚体含量、团聚体平均质量直径和团聚体稳定率,且随有机肥用量的增加而显著增加;中、高量有机肥处理比单施化肥处理增加效果显著.