联合施用不同植物物质和鸡粪对土壤碳氮含量和蔬菜产量的影响

The use of plant materials as soil amendments is an uncommon practice amongst major farming communities in Ghana, although it is necessary for soil fertility improvement. An examination of the effects of soil amendments is necessary to encourage the use of under-utilized organic resources in Ghana. Thus, a field experiment was conducted using 8 different tropical plant materials mixed with chicken manure as soil amendments for growth of tomato as a test crop. The plant materials included Leucaena leucocephala, Centrosema pubescens, Sesbania sesban, Gliricidia sepium, Mucuna pruriens, Pueraria phaseoloides, Azadirachta indica, and Theobroma cacao. There were two other treatments: one with equivalent amounts of chemical fertilizers and the other with no-fertilizer input (control). Plant materials were mixed with chicken manure to obtain a uniform carbon-to-nitrogen (C:N) ratio of 5:1. Except the no-fertilizer control, all treatments received the same amount of nitrogen (N). To clarify the decomposition pattern of the plant materials in soil, an incubation experiment was conducted using only the plant materials before the field experiment. The Gliricidia treatment released significantly more mineral N than the other plant materials in the incubation experiment. However, the tomato fruit yield was not enhanced in the Gliricidia treatment in the field experiment. The known quality parameters of the tested plant materials, such as total N, total carbon (C), C:N ratio, and total polyphenols, had minimal effects on their mineralization dynamics. Azadirachta showed the best synergistic effect with chicken manure through significantly increasing soil microbial biomass and fruit yield of tomato. This result provides insights into the possible adoption of Azadirachta in combination with chicken manure as a soil amendment in small-scale agricultural holdings.     

复配改良剂表施对高降雨量地区茶园底层强酸性土壤酸度的调控

Strongly acidic soils (pH < 5.0) are detrimental to tea (Camellia sinensis) production and quality. Little information exists on the ability of surface amendments to ameliorate subsoil acidity in the tea garden soils. A 120-d glasshouse column leaching experiment was conducted using commonly available soil ameliorants. Alkaline slag (AS) and organic residues, pig manure (PM) and rapeseed cake (RC) differing in ash alkalinity and C/N ratio were incorporated alone and in combination into the surface (0--15 cm) of soil columns (10 cm internal diameter × 50 cm long) packed with soil from the acidic soil layer (15--30 cm) of an Ultisol (initial pH = 4.4). During the 120-d experiment, the soil columns were watered (about 127 mm over 9 applications) according to the long-term mean annual rainfall (1 143 mm) and the leachates were collected and analyzed. At the end of the experiment, soil columns were partitioned into various depths and the chemical properties of soil were measured. The PM with a higher C/N ratio increased subsoil pH, whereas the RC with a lower C/N ratio decreased subsoil pH. However, combined amendments had a greater ability to reduce subsoil acidity than either of the amendments alone. The increases in pH of the subsoil were mainly ascribed to decreased base cation concentrations and the decomposition of organic anions present in dissolved organic carbon (DOC) and immobilization of nitrate that had been leached down from the amended layer. A significant (P < 0.05) correlation between alkalinity production (reduced exchangeable acidity -- N-cycle alkalinity) and alkalinity balance (net alkalinity production -- N-cycle alkalinity) was observed at the end of the experiment. Additionally, combined amendments significantly increased (P < 0.05) subsoil cation concentrations and decreased subsoil Al saturation (P < 0.05). Combined applications of AS with organic amendments to surface soils are effective in reducing subsoil acidity in high-rainfall areas. Further investigations under field conditions and over longer timeframes are needed to fully understand their practical effectiveness in ameliorating acidity of deeper soil layers under naturally occurring leaching regimes.     

Contribution of soluble and insoluble fractions of agricultural residues to short‐term pH changes

The retention of agricultural residues in cropping systems to maintain soil fertility is also important for the redistribution of alkalinity. In systems that adopt minimum or no‐tillage practices residue incorporation into the soil may occur slowly and the contribution of soluble and insoluble residue fractions to pH change may vary temporally and spatially. In this study we examined the contribution of whole, water soluble (70°C for 1 hour for two cycles) and insoluble fractions of canola, chickpea and wheat residues (added at 10 g kg^?1 soil) to pH change in a Podosol (Podzol; initial pH 4.5) and a Tenosol (Cambisol; initial pH 6.2) over a 59‐day incubation period. Whole residues increased pH in both soils, with the magnitude of the pH increase (chickpea > canola > wheat) being related to alkalinity content (concentration of excess cations) of the residue. Temporal release of alkalinity was only observed for the larger alkalinity content canola and chickpea residues and the change in pH was greater than during the initial period (approximately 4 hours; T0). Increases in pH were attributed to the decarboxylation of organic anions and the association of H⁺ with organic anions and other negatively charged chemical functional groups. The relative contribution of these processes depended on the residue and the initial soil pH. Our results show that 40–62% of the alkalinity of canola and chickpea residues resided in the soluble fraction. Furthermore, pH increases caused by soluble fractions may be transient if these contain large N concentrations. Soil properties that influence inorganic N dynamics such as inhibition of nitrification at acid pH will be important in determining the subsequent direction and magnitude of pH change.     

EFFECT OF SOIL AMENDMENT WITH THIN STILLAGE AND GLYCEROL ON PLANT GROWTH AND SOIL PROPERTIES

Controlled environment experiments were set up in 2007 and 2008 to evaluate the potential of using by-products of the biofuel industry as soil amendments to improve fertility and plant growth in Saskatchewan soils. Trials were run with thin stillage (a by-product of ethanol production) and glycerol (by-product of biodiesel production). Canola (B. napus L.) and wheat (T. aestivum) were grown as the test crop in amended pots. Plant yield, composition, and soil properties were measured after five weeks. The stillage was found to be an effective soil amendment for increasing plant biomass yield. Per unit of nitrogen (N) added, canola yields were less than that of urea when nitrogen was the only limitation, due to only a portion of the nitrogen in the thin stillage becoming available over the five week period. However, when nutrients other than nitrogen were limiting, canola dry matter yields with thin stillage amendment approached or exceeded that of urea, due to the ability of the amendments to supply other nutrients such as phosphorus in addition to nitrogen. Glycerol, an amendment that only contains carbon, hydrogen and oxygen, was effective in increasing soil organic carbon content, but required supplemental fertilizer to account for nutrient tie-up by microorganisms during decomposition in the soil. The amendments did not have any biologically significant effects on other soil chemical parameters measured, including soluble metals, pH or salinity.     

Use of crop residues with alkaline slag to ameliorate soil acidity in an Ultisol

Information regarding the interaction between liming agents and crop residues on soil acidity amelioration is limited. A laboratory incubation study was undertaken to investigate the combined application of alkaline slag (AS, the major component is CaO) and crop residues with different C/N ratios and ash alkalinity content. Incorporation of amendments was effective in reducing soil exchangeable acidity and Al saturation and increasing exchangeable base cations (P < 0.05), but the effect of AS on soil pH adjustment was reduced when added with a high amount of residue with a low C/N ratio. Initial increases in soil pH were attributed to the release of alkalinity from the combined amendments and the mineralization of organic nitrogen (N). During subsequent incubation, the soil pH decreased because of nitrification. Crop residues with a high C/N ratio increased N immobilization and reduced net nitrification, resulting in a slight pH decrease. Crop residues with a low C/N ratio resulted in a sharp decrease in soil pH when applied with low levels of AS because of stimulated soil nitrification, whereas high AS had no consistent effect on net nitrification. Hence, compared to the control (pH = 4.21), a large increase in soil pH occurred, especially when peanut straw was applied at 10 g/kg (pH = 5.16). It is suggested that crop residues with high C/N ratio and also combined with a liming agent such as AS are preferred to ameliorate soil acidity. The liming effect of AS is likely to be negated if added in combination with residues with high N contents.     

EFFECT OF SOIL AMENDMENT WITH ALFALFA POWDERS AND DISTILLERS GRAINS ON NUTRITION AND GROWTH OF CANOLA

Two pot experiments were carried out under controlled environment conditions in the growth chamber to assess the potential use of alfalfa powders and distiller grains as organic fertilizers. Two types of dehydrated alfalfa powders (one with canola meal protein extraction by-product and one without) and two types of distiller grains (dried distillers grain with distillation solubles added and wet distillers grain without solubles) from wheat-based ethanol production were evaluated. Four different nitrogen (N)-based amendment application rates (0, 100, 200 and 400 kg N ha^?1) were used along with urea applications made at the same N rates to a Brown Chernozem (Aridic Haploboroll) loamy textured soil collected from south-central Saskatchewan, Canada. Canola biomass yield, N, phosphorus (P), potassium (K), zinc (Zn), and cadmium (Cd) uptake were measured along with soil properties including pH, salinity, organic carbon, total nitrogen, phosphorus and extractable nutrients and cadmium before and after canola growth in each of the treatments. Application of alfalfa powder and distiller grain amendments resulted in significant canola biomass yield increases along with increased N, P, and K uptake compared to the unfertilized control. However, only a portion of the N added (～30% to 50%) in the organic amendments was rendered available over the five week duration of the experiments. Amendments that had higher N content and lower carbon (C):N ratios such as dried distillers grain with solubles resulted in greater canola N uptake. Reduced germination and emergence of canola seedlings was observed at high rates of addition of distillers grain (400 kg N ha^?1), the reason for which is unclear but may be due to a localized salt or toxicity effect of the amendment. The amendment with alfalfa powders and distiller grains resulted in small increases in residual soil nutrients. Effects on pH, salinity, organic carbon and extractable metals tended to be small and often not significant. Alfalfa powders and distillers grains appear to be quite effective in supplying nutrients, especially N, for plant growth over the short-term.     

ESTIMATING SHORT- AND MEDIUM-TERM AVAILABILITY TO CEREALS OF NITROGEN FROM ORGANIC RESIDUES

Overused soil resources and the build-up of organic residues from industrial processes have resulted in increased risk of environmental contamination. Recycling of organic residues from industry by incorporation into agricultural soil, can provide valuable organic amendment as well as supply nutrients to crops. The effect of applying organic amendments to an agricultural sandy soil on the nitrogen nutrition of wheat (Triticum aestivum L.) and residual effects on the growth of a following maize crop (Zea mays, L.), were assessed under semi-controlled environmental conditions and were compared to nitrogen mineralization prediction obtained from an aerobic incubation. Six different organic residues (composted municipal solid waste, secondary pulp-mill sludge, hornmeal, poultry manure, the solid phase from pig slurry and composted pig manure) were added to a Cambic arenosol, incubated or used in pot experiments, to evaluate and try to predict the availability to crop plants of nitrogen released from these materials. Poultry manure was the most effective amendment in making nitrogen available and enhancing nitrogen uptake by wheat plants resulting in greater dry matter yield. The dried solid phase from pig slurry and hornmeal were also beneficial to wheat growth. There was a greater recovery of nitrogen (N), from organic materials studied, by a maize crop. Poultry manure was the residue that provided a greater residual effect on N supply to maize.     

Immobilization and mineralization of nitrogen in a saline and alkaline soil during microbial use of sugarcane filter cake amended with glucose

A 42-day incubation was conducted to study the effect of glucose and ammonium addition adjusted to a C/N ratio of 12.5 on sugarcane filter cake decomposition and on the release of inorganic N from microbial residues formed initially. The CO₂ evolved increased in comparison with the non-amended control from 35% of the added C with pure +5 mg g⁻¹ soil filter cake amendment to 41% with +5 mg g⁻¹ soil filter cake +2.5 mg g⁻¹ soil glucose amendment to 48% with 5 mg g⁻¹ soil filter cake +5 mg g⁻¹ soil glucose amendment. The different amendments increased microbial biomass C and microbial biomass N within 6 h and such an increase persisted. The fungal cell-membrane component ergosterol initially showed a disproportionate increase in relation to microbial biomass C, which completely disappeared by the end of the incubation. The cellulase activity showed a 5-fold increase after filter cake addition, which was not further increased by the additional glucose amendment. The cellulase activity showed an exponential decline to values around 4% of the initial value in all treatments. The amount of inorganic N immobilized from day 0 to day 14 increased with increasing amount of C added, in contrast to the control treatment. After day 14, the immobilized N was re-mineralized at rates between 1.3 and 1.5 μg N g⁻¹ soil d⁻¹ in the treatments being more than twice as high as in the control treatment. This means that the re-mineralization rate is independent of the actual size of the microbial residues pool and also independent of the size of the soil microbial biomass.     

Soil microbial community structure affected by 53 years of nitrogen fertilisation and different organic amendments

The Ultuna long-term soil organic matter experiment in Sweden (59′82° N, 17′65° E) was started in 1956 to study the effects of different N fertilisers and organic amendments on soil properties. In this study, samples were taken from 11 of the treatments, including unfertilised bare fallow and cropped fallow, straw with and without N addition, green manure, peat, farmyard manure, sawdust, sewage sludge, calcium nitrate and ammonium sulphate, with n = 4 for each treatment. Samples were taken from topsoil (0–20 cm) and subsoil (27–40 cm depth) and analysed for concentrations of phospholipid fatty acids (PLFAs), organic C, total N and pH. The results showed that the subsoil samples reflected the total PLFA content of the topsoil, but not the microbial community structure. Total PLFA content was well correlated with total organic C and total N in both topsoil and subsoil. Total PLFA content in topsoil samples was highest in the sewage sludge treatment (89 ± 22 nmol PLFA g dw⁻¹). This contradicts earlier findings on microbial biomass in this sewage sludge-treated soil, which indicated inhibition of microorganisms, probably by heavy metals added with sludge. A switch towards microbial growth and faster decomposition of organic matter occurred around 2000, coinciding with lowered heavy metal content in the sludge. According to the PLFA data, the microbial community in the sewage sludge treatment is now dominated by Gram-positive bacteria. A lack of Gram-negative bacteria was also observed for the ammonium sulphate treatment, obviously caused by a drop in pH to 4.2.     

Nutritional Values of Some Biowastes As Soil Amendments

As a result of increased population, improved standards of living, and strict environmental laws, biowastes have been generated in huge quantities. Thus, land applications of these wastes are desirable, or even necessary, to keep the environment healthy and to conserve natural resources. Yet, the success of such uses requires knowledge of complex biochemical reactions when the wastes are applied to soils. To obtain this knowledge, we evaluated soil amendment properties, primarily nitrogen (N) mineralization/immobilization of six bio wastes when used as plant growth media. An immature yard trimmings compost, ground fresh corn stovers, a commercial peat moss, a chicken manure, and two biosolids were each mixed with a Mollisol at either 25 percent and 50 percent by volume for the plant based wastes, or at 2.5 percent and 5.0 percent by weight for the animal based wastes. Treatments with urea at 0, 70 and 210 mg N kg^?1 were included for comparison. The treated soils were incubated moist for two weeks at which time they were sampled for chemical analysis, and planted to tomatoes. The results showed that those wastes, when added to soil, produced growth media with C/N < 15, and released inorganic N that increased dry matter yield of tomatoes many times over that of the unamended control. In contrast, a waste amended soil with a C/N > 20 immobilized some inorganic N, reduced plant growth, and caused N deficiency in tomatoes. Such a deficiency was characterized by low N concentrations in leaves (< 2.0 percent) and chlorosis, which corresponded to a color index of 0.25 or less. Biowaste amendments also affected soil P extractability differently: Chicken manure increased NaHCO₃-extractable P many fold over the control, whereas corn stover, peat moss and raw biosolids did not. The yard trimmings compost and the anaerobically digested biosolids increased soil P moderately.     

The response of soil organic matter to manure amendments in a long-term experiment at Ultuna, Sweden

In a long-term field experiment started in 1956 on a clay loam soil at Uppsala, Sweden, changes of organic carbon in the topsoils receiving various organic amendments at the rate of 200 kg C ha^'1 year^'1 were studied to determine soil organic matter characteristics, variations of δ¹³C in the soil and to estimate a carbon balance. Fallow and mineral fertilizer without N led to a significant decrease of soil organic matter (SOM) in the soil, green manure maintained the SOM content, and animal manure and peat increased the SOM content significantly. The stable portion of the added organic materials after 37 years of continuous input was 12·8, 27·3, and 56·7%, for green manure, animal manure and peat, respectively. This was reflected by half-lives of organic carbon originating from the amendments between 3·0 (green manure) and 14·6 years (peat). The isotopic composition of SOM changed both due to mineralization (continuous fallow) and the addition of amendments is topically different from soil humus (green manure, animal manure). The isotopic effect was used to calculate the percentage of carbon derived from animal manure present for the year 1993. This value (55·4%) was larger than that derived from the carbon balance, which indicated a priming effect of the animal manure on the initial soil humus. Mineralization of microbially available organic substances led to an increase in the degree of humification on plots not receiving organic amendments. Adding peat and animal manure resulted in a decrease of the humification index due to the continuous input of poorly humified material. The extinction ratio (E₄/E₆) and ratio of fulvic acid to humic acid changed considerably in the peat treated plots. Fourier transform infrared (FTIR)-measurements of the extracts showed that peat characteristics can be detected in peat treated soils. The other amendments did not alter the characteristics of the extractable humic substances.     

Effect of swine and dairy manure amendments on microbial communities in three soils as influenced by environmental conditions

Understanding the impacts of manure amendments on soil microorganisms can provide valuable insight into nutrient availability and potential crop and environmental effects. Soil microbial community characteristics, including microbial populations and activity, substrate utilization (SU) profiles, and fatty acid methyl ester (FAME) profiles, were compared in three soils amended or not amended with dairy or swine manure at two temperatures (18 and 25°C) and two soil water regimes (constant and fluctuating) in laboratory incubation assays. Soil type was the dominant factor determining microbial community characteristics, resulting in distinct differences among all three soil types and some differing effects of manure amendments. Both dairy and swine manures generally increased bacterial populations, substrate diversity, and FAME biomarkers for gram-negative organisms in all soils. Microbial activity was increased by both manures in an Illinois soil but only by dairy manure in two Maine soils. Dairy manure had greater effects than swine manure on SU and FAME parameters such as increased activity, utilization of carbohydrates and amino acids, substrate richness and diversity, and fungal FAME biomarkers. Temperature and water regime effects were relatively minor compared with soil type and amendment, but both significantly affected some microbial responses to manure amendments. Overall, microbial characteristics were more highly correlated with soil physical factors and soil and amendment C content than with N levels. These results indicate the importance of soil type, developmental history, and environmental factors on microbial community characteristics, which may effect nutrient availability from manure amendments and should be considered in amendment evaluations.Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture     

Flow-associated precipitation reactions in saline-sodic soils and their significance

A saline-sodic soil (pH 10.0, ESP 100.0, total soluble salts 10.0 mequiv./100 g) rich in soluble sodium carbonate (7.8 mequiv./100 g) was leached in the laboratory with calcium-containing water. The effect of varying flow velocities and concentration of calcium in the leaching water on the extent of carbonate precipitation was studied by following the composition of leachate in one set of experiments and the redistribution of soluble carbonates in the soil column in another experiment. The results showed that precipitation of soluble carbonates in the soil increased with increasing flow velocity and concentration of calcium in the leaching solution. The results have been discussed in terms of actual flow processes occurring at the wetting front. It is suggested that by controlling the extent of carbonate precipitation, the quantity of amendments containing calcium necessary for the reclamation of sodic soils rich in soluble carbonates can be considerably reduced. The results also suggest that the usual method of determining the gypsum requirement of soils is likely to overestimate the gypsum needs of these soils because a large portion of the soluble carbonates is leached out without reaction with the added gypsum.     

Soil biological properties and carbon dynamics subsequent to organic amendments addition in sodic black soils

The field experiments on calcareous sodic Vertisols were conducted on farmer’s fields in Purna valley of Vidarbha region of Maharashtra. The treatments comprised of different green manures (GMs); crop residues (CRs); gypsum. The chemical and biological properties after 2 years experiment showed that the application of gypsum recorded significant drop in pH and exchangeable sodium percentage (ESP) as compared to organic amendments. But later has outperformed with respect to biological activities viz., dehydrogenase activity (DHA) and microbial respiration and carbon sequestration by enhancing soil organic carbon (SOC), soil organic carbon (SOC) stock, soil microbial biomass carbon (SMBC) and labile carbon pool (POXC). Among the different organic amendments the application of dhaincha improved SMBC by 90%, microbial respiration by 104%, POXC by 59% and DHA by 265% as compare to control. High ESP of these soils showed negative relationship with microbial respiration and POXC (r = 0.48 and r = 0.43, p = < 0.05). While addition of biomass showed positive relationship with SMBC, microbial respiration, POXC and DHA (r = 0.93, r = 0.81, r = 0.83 and r = 0.91 p = < 0.01). The results of study showed green manuring in sodic black soil found to be alternative choice to gypsum, which besides gradual reclamation also enhance biological properties and carbon sequestration.     

有机物料对强酸性茶园土壤的酸度调控研究

通过室内培养的方式,研究了不同添加剂量下,不同C/N与灰化碱含量的有机物料对酸性茶园土壤的改良能力.试验结果表明:有机物料的添加可以有效地减少土壤交换性酸、铝饱和度,增加土壤交换性碱基,但是在调节土壤pH能力上并非一定有效.初始阶段,“灰化碱”的释放与有机氮的矿化提高了土壤的pH,随后pH由于硝化作用出现不同程度的下降.C/N高的作物秸秆(小麦和水稻秸秆)能够有效地抑制硝化,使pH下降幅度较小;而C/N低的作物秸秆(花生秸秆和菜籽饼)促进硝化,使pH大幅度下降.最终土壤pH与其C/N呈正相关性(y=0.00343x+4.14,r=0.977),而与其灰化碱含量无关.并且随着秸秆添加剂量的加大,C/N高的作物秸秆最终调剂pH的能力是显著提高的(P＜0.05),而C/N低的作物秸秆最终调剂pH的能力没有显著提高(P＜0.05).因此,C/N高的作物秸秆可能更适合土壤酸度的长期调节,与其相关的田间试验需要进一步进行证实.     

Influence of Long‐Term Sodic‐Water Irrigation,Gypsum, and Organic Amendments on Soil Properties and Nitrogen Mineralization Kinetics under Rice–Wheat System

Abstract

Influence of long‐term sodic‐water (SW) irrigation with or without gypsum and organic amendments [green manure (GM), farmyard manure (FYM), and rice straw (RS)] on soil properties and nitrogen (N) mineralization kinetics was studied after 12 years of rice–wheat cropping in a sandy loam soil in northwest India. Long‐term SW irrigation increased soil pH, exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR) and decreased organic carbon (OC) and total N content. On the other hand, application of gypsum and organic amendments resulted in significant improvement in all these soil properties. Mineralization of soil N ranged from 54 to 111 mg N kg^?1 soil in different treatments. Irrigation with SW depressed N mineralization. In SW‐irrigated plots, two flushes of N mineralization were observed; the first during 0 to 7 d and the second after 28 d. Amending SW irrigated plots with GM and FYM enhanced mineralization of soil N. Gypsum application along with SW irrigation reduced cumulative N mineralization at 56 days in RS‐amended plots but increased it under GM‐treated, FYM‐treated, or unamended plots. Nitrogen mineralization potential (N_o) ranged from 62 to 543 mg N kg^?1 soil. In the first‐order zero‐order model (FOZO), the easily decomposable fraction ranged from 5.4 to 42 mg N kg^?1 soil. Compared to the first‐order single compartment model, the FOZO model could better explain the variations in N mineralization in different treatments. Variations in N_o were influenced more by changes in pH, SAR, and ESP induced by long‐term SW irrigations and amendments rather than by soil OC.     

The influence of blue-green algae on the biological amelioration of alkali soils

Summary Virgin alkali (sodic) soils have a high pH and high exchangeable Na and are often barren. Blue-green algae, however, tolerate excess Na and grow extensively on the soil surface in wet seasons. Experiments using a highly degraded alkali soil (silt loam, pH 10.3, electrical conductivity 3.5 dS m^-1, 90% exchangeable Na) were conducted in soil columns, with or without gypsum, in order to study the influence of waterlogging on the growth of indigenous and inoculated blue-green algae and hence, soil reclamation. The growth of indigenous blue-green algae was initially slow in alkali soil, due to the high pH and exchangeable Na, and depressed in gypsum-amended soil, due to excess Ca. Inoculation hastened the establishment of blue-green algae in both the unamended alkali soil and the gypsum-amended soil, overcoming the adverse influence of excess Na in the former and excess Ca in the latter. Gypsum was effective in amelioration (pH 9.05, electrical conductivity 1.2 dS m^-1, 41% exchangeable Na after 11 weeks) but blue-green algae were ineffective even after 17 weeks. In combination with gypsum, blue-green algae had no additional effect, and the C and N increases due to the growth of indigenous or inoculated blue-green algae were insignificant.Alkali soil reclamation by biological methods requires mobilization of Ca from native soil calcite and the exchange of Ca for Na in the exchange complex. The ineffectiveness of blue-green algae was ascribed to their inability to mobilize Ca. It is argued that current theories favouring blue-green algae as a biological amendment to bring about alkali soil reclamation are untenable and are not comparable with an effective chemical amendment such as gypsum.     

The liming effect of five organic manures when incubated with an acid soil

A laboratory incubation experiment of 6 months duration was carried out to investigate the liming effects of five organic manures (poultry, pig, and cattle manure, soybean residues, and sewage sludge) when added to an acid soil at a rate of 10 mg g^–1. Soils were sampled after 1, 7, 13, 19, and 25 weeks of incubation. For the animal manures and sewage sludge, soil pH was highest after 1 week incubation and it declined thereafter. However, for soybean residues, pH increased over the first 7 weeks of incubation after which it declined. The decreases in pH were accompanied by accumulation of NO ‐N in the soil. The addition of organic residues to the soil resulted in decreases in the concentrations of exchangeable Al and in both total (Al_t) and monomeric (Al_mono) Al present in the soil solution. The effect was most marked for poultry manure, least marked for cattle manure, and more evident after 7 than 25 weeks incubation. Concentrations of soluble C in the soil solution were elevated in manure‐amended soils. Manure additions resulted in a decrease in the percentage of Al_t present in solution as Al_mono, and this was attributed to complexation of Al by soluble organic matter originating from the manures. It was concluded that organic wastes can act as liming materials when added to acid soils and that the resulting increase in pH and decrease in Al_mono concentrations might provide a window of opportunity for establishment and early growth of crop plants.     

Use of langbeinite to reclaim sodic and saline sodic soils

Abstract

Langbeinite is a soluble potassium‐magnesium sulfate mineral (K₂SO₄2MgSO₄) found as an evaporite in many regions of the world. Langbeinite was used as a reclaiming material in a fine textured (clay loam) saline sodic soil (Grabe Series). This amendment can be dissolved and directly into the irrigation water, displacing sodium (Na) quickly with minimal water use. This amendment was superior over gypsum as a reclaiming material for a saline sodic soil in batch, column, and greenhouse studies. Langbeinite required 50% less irrigation water than gypsum to displace and leach exchangeable Na from soils. Langbeinite improved the infiltration rates of saline sodic soils, but not as effectively as gypsum. Significant increases in germination percent dry matter production mass of lima bean (Phaseolus lunatus L.) plants were observed when using langbeinite over the gypsum soil amendment.     

Release Kinetics of Some Nutrients from a Sandy Loam Soil Treated with Different Organic Amendments

ABSTRACT

An incubation study was undertaken to examine the periodic release of some macronutrients and micronutrients in a sandy loam treated with different organic amendments (farmyard manure, mushroom compost, poultry manure, vermicompost, biogas slurry, and biochar of Lantana weed) added @ 15 t ha^?1 for 120 d through entrapment of released nutrients on ion exchange resins. Among organic amendments, the highest total contents were recorded for Ca, Mg, and S in farmyard manure, for K, Fe, and Mn in mushroom compost, for P, Zn, and Cu in biogas slurry, for B in biochar. The highest average release was recorded for P, Zn, Mn, and B from poultry manure, for Cu from biogas slurry, for Fe from vermicompost, for Ca, Mg, and S from mushroom compost, and for K from farmyard manure. The kinetics of mineralization and release of these nutrients conformed well to the zero-order kinetics and also to a power function equation. The initial release amount and release rate coefficient estimated by the power function equations were correlated significantly to the general properties of organic amendments and also to the type of C species present in organic amendment. Organic amendments having relatively higher content of water soluble C or fulvic or humic acids are likely to release nutrients through an early mineralization/solubilization from soil reserve.