Salt-tolerant forage cultivation on a saline-sodic field for biomass production and soil reclamation

Chemical reclamation of sodic and saline-sodic soils has become cost-intensive. Cultivation of plants tolerant of salinity and sodicity may mobilize the CaCO₃ present in saline-sodic soils instead of using a chemical approach. Four forage plant species, sesbania (Sesbania aculeata), kallar grass (Leptochloa fusca), millet rice (Echinochloa colona) and finger millet (Eleusine coracana), were planted in a calcareous saline-sodic field (EC_e = 9·6–11·0 dS m⁻¹, SAR = 59·4–72·4). Other treatments included gypsum (equivalent to 100 per cent of the gypsum requirement of the 15 cm soil layer) and a control (no gypsum or crop). The crops were grown for 5 months. The performance of the treatments in terms of soil amelioration was in the order: Sesbania aculeata ≅ gypsum > Leptochloa fusca > Echinochloa colona > Elusine coracana > control. Biomass production by the plant species was found to be directly proportional to their reclamation efficiency. Sesbania aculeata produced 32·3 Mg forage ha⁻¹, followed by Leptochloa fusca (24·6 Mg ha⁻¹), Echinochloa colona (22·6 Mg ha⁻¹) and Eleusine coracana (5·4 Mg ha⁻¹). Sesbania aculeata emerged as the most suitable biotic material for cultivation on salt-affected soils to produce good-quality forage, and to reduce soil salination and sodication processes.     

Rehabilitation of alkaline wasteland on the gangetic alluvial plains of Uttar Pradesh,India, through afforestation

A few species of fuelwood trees were established on highly alkaline wasteland at Aligarh (27°5′ N., 78°4′ E.) in a tropical environment. Of these Prosopis juliflora produced maximum biomass (12.05 t ha⁻¹) and had an energy content of 242.11 GJ ha⁻¹ after 3.5 years growth period. The survival percentage of Terminalia arjuna was highest of those the species tried, but their growth and biomass production were inferior to that of Prosopis juliflora and Acacia nilotica. Some of the fuelwood tree plantations were raised without adding any soil amendment but suffered heavy mortality and could not produce any significant quantity of biomass. In another experiment Leucaena leucocephala was identified as a most promising species for afforestation on substandard soils; also it was found that a relatively high population density (of about 7,500 plants per hectare) is required to rehabilitate such land. Of the soil amendments tried, gypsum with farmyard manure and sand in equal proportion gave the better response (gypsum alone was also tried). Two species of shrubs: Sesbania sesban and Tamarix dioca have shown good adaptability in difficult habitats. After five years of afforestation the soil properties of the sites improved significantly, showing marked reduction in pH, EC and ESP values and an increase in organic carbon content.     

Growth and selenium uptake of range plants propagated in uranium mine soils

High soil selenium (Se) levels have been found in association with uranium deposits in Texas. A concern that high Se concentrations may be found in forages grown on reclaimed mine lands prompted this investigation. A native soil sampled near the mining area, and overburden materials sampled from two Se enriched uranium mine spoil sites were compared in a plant growth study in the greenhouse. Shoot yields and shoot Se concentration in each of ten grasses common to the region were determined from plants harvested three weeks after germination and from shoot regrowth harvested four weeks after the first harvest. Shoot weights were reduced for 5 of the 10 species growing in soils with medium and high Se status. Total shoot weights of Cynodon dactylon and Panicum coloratum from two harvests were consistently highest in all soil materials and are highly recommended for use as a stabilizing cover crop for lands disturbed from uranium mining. Generally, no correlation was observed between shoot weight and plant Se concentration or uptake in the 10 species. However, plant tissue Se concentrations in all species for at least one of the two harvest dates were above the 5 mg kg^‐1 concentration considered potentially harmful to grazing livestock. Therefore, none of these species would be a suitable forage for livestock grazing on reclaimed Se‐enriched uranium mining overburden.     

Growing three aromatic grasses in different alkali soils in semi‐arid regions of northern India

Alkali lands in India occupy about 3 million ha. Due to poor physical properties, excessive exchangeable sodium and high pH, most of these lands support a very poor vegetation cover. Many of the medicinal and aromatic plants are in great demand for both internal requirements and export. But since these crops are non‐conventional in nature, it is not always possible for them to be produced on fertile lands, which can be used for arable crops. The marginal lands, specifically the lands affected by salinity or sodicity problems where profitable returns are not possible from agricultural crops, could be successfully utilized for the cultivation of these high‐value crops with marginal inputs. Results reported in this paper clearly indicated that out of three aromatic grasses, palmarosa (Cymbopogon martinii (Roxb.) Wats.) and lemon grass (C. flexuosus (Steud.) Wats.) could successfully be grown on moderatly alkali soils of pH up to 9·2 while vetiver (Vetiveria zizanioides (L.) Nash), which withstands both high pH and stagnation of water, could successfully be grown without significant yield reduction on highly alkali soils. These grasses not only produce essential oils used for industrial purposes but also ameliorate the soil. Copyright © 2004 John Wiley & Sons, Ltd.     

Raised and sunken bed technique for agroforestry on alkali soils of northwest India

Many forest tree and fruit species can be raised on highly alkali soil (pH > 10) but some of them such as pomegranate (Punica granatum) are unable to tolerate water stagnation. To avoid water stagnation problems during the monsoon the raised and sunken bed technique has been found suitable for agroforestry practices on highly alkali soil. One fruit‐yielding pomegranate and one oil‐yielding salvadora (Salvadora persica) plantation species were successfully grown on raised bunds to avoid water stagnation and rice–wheat and berseem–kallar grass rotation were grown on sunken‐beds constructed for the purpose. The experiment was initiated in 1996 and the above two crop rotations were followed for two consecutive years starting in the summer season. Results of these experiments have also shown that good growth of plantations, on an average 4·3 to 4·9 t ha⁻¹ rice (salt tolerant var. CSR‐10) and 1·2 to 1·4 t ha⁻¹ wheat (KRL 1–4), were obtained in sunken beds. In another rotation 21·3 to 36.8 t ha⁻¹ fresh forage of kallar grass (Leptochloa fusca) and 44·9 to 47·8 t ha⁻¹ fresh forage of berseem (Trifolium alexandrium) were obtained. After two years of the experiment, soil amelioration in terms of reduction in soil pH was significant. The effect of plantation in reducing soil pH showed that the pomegranate and salvadora both helped in reduction of soil pH, but the latter due to its well‐developed lateral root system was more efficient in lowering the soil pH even at lower depths. The reduction in soil pH by the berseem–kallar grass rotation was better than under rice–wheat rotation. Copyright © 2001 John Wiley & Sons, Ltd.     

Salt-affected soils,reclamation, carbon dynamics,and biochar: a review

Purpose

This paper reviews chemical, physical, and biological problems of salt-affected soils and different reclamation methods applied to rehabilitate these soils.

Methods

Methods to increase C stocks in these lands are discussed with a focus on biochar application as a potential new approach to not only to increase the C content but also to improve soil properties. Gaps in research knowledge in this field are then identified.

Results

Given the concern on the continued worldwide expansion of salt-affected lands and the focus on C sequestration processes, this review has evaluated current knowledge on salt-affected soils and their remediation with organic materials and plants. The review of the published literature has highlighted important gaps in knowledge, which limit our current understanding of rehabilitation of salt-affected soils with organic amendments specially biochar and the associated carbon dynamic. Knowledge about application of biochar in salt-affected soils is scant, and to date, most studies have evaluated biochar use only in nonsalt-affected soils.

     

Soil organic carbon stock for reclaimed minesoils in northeastern Ohio

Reclamation of disturbed soils is done with the primary objective of restoring the land for agronomic or forestry land use. Reclamation followed by sustainable management can restore the depleted soil organic carbon (SOC) stock over time. This study was designed to assess SOC stocks of reclaimed and undisturbed minesoils under different cropping systems in Dover Township, Tuscarawas County, Ohio (40°32·33′ N and 81°33·86′ W). Prior to reclamation, the soil was classified as Bethesda Soil Series (loamy‐skeletal, mixed, acid, mesic Typic Udorthent). The reclaimed and unmined sites were located side by side and were under forage (fescue—Festuca arundinacea Schreb. and alfa grass—Stipa tenacissima L.), and corn (Zea mays L.)—soybean (Glycine max (L.) Merr.) rotation. All fields were chisel plowed annually except unmined forage, and fertilized only when planted to corn. The manure was mostly applied on unmined fields planted to corn, and reclaimed fields planted to forage and corn. The variability in soil properties (i.e., soil bulk density, pH and soil organic carbon stock) ranged from moderate to low across all land uses in both reclaimed and unmined fields for 0–10 and 10–20 cm depths. The soil nitrogen stock ranged from low to moderate for unmined fields and moderate to high in some reclaimed fields. Soil pH was always less than 6·7 in both reclaimed and unmined fields. The mean soil bulk density was consistently lower in unmined (1·27 mg m⁻³ and 1·22 mg m⁻³) than reclaimed fields (1·39 mg m⁻³ and 1·34 mg m⁻³) planted to forage and corn, respectively. The SOC and total nitrogen (TN) concentrations were higher for reclaimed forage (33·30 g kg⁻¹; 3·23 g kg⁻¹) and cornfields (21·22 g kg⁻¹; 3·66 g kg⁻¹) than unmined forage (17·47 g kg⁻¹; 1·98 g kg⁻¹) and cornfield (17·70 g kg⁻¹; 2·76 g kg⁻¹). The SOC stocks in unmined soils did not differ among forage, corn or soybean fields but did so in reclaimed soils for 0–10 cm depth. The SOC stock for reclaimed forage (39·6 mg ha⁻¹ for 0–10 cm and 28·6 mg ha⁻¹ for 10–20 cm depths) and cornfields (28·3 mg ha⁻¹; 32·2 mg ha⁻¹) were higher than that for the unmined forage (22·7 mg ha⁻¹; 17·6 mg ha⁻¹) and corn (21·5 mg ha⁻¹; 26·8 mg ha⁻¹) fields for both depths. These results showed that the manure application increased SOC stocks in soil. Overall this study showed that if the reclamation is done properly, there is a large potential for SOC sequestration in reclaimed soils. Copyright © 2005 John Wiley & Sons, Ltd.     

An inventory of salt-affected soils and waterlogged areas in the Nagarjunsagar Canal Command Area of southern India,using space-borne multispectral data

Information is presented on the nature, extent and spatial distribution of waterlogged areas and salt-affected soils, derived through systematic visual interpretation of standard false colour composite (FCC) prints on a 1:100 000 scale generated from the Indian Remote Sensing Satellite (IRS-1B) Linear Imaging Self-scanning Sensor (LISS-I) and Landsat–Thematic Mapper (TM) data for the Nagarjunsagar Right Bank Canal Command Area, Andhra Pradesh. A total of 1710 ha of land in the coastal region has been found to be waterlogged. Salt-affected soils cover an area of 42 800 ha, with saline–sodic soils covering 28 480 ha emerging as the dominant category. To make optimal use of these lands and to prevent further degradation both preventive and ameliorative measures have been advocated. © 1998 John Wiley & Sons, Ltd.     

Land-use management for sustainable rice production and carbon sequestration in reclaimed coastal tideland soils of South Korea: a review

ABSTRACT

The properties of secondary salt-affected soils developed from improper irrigation and drainage management and their effects on rice growth and yield are well documented. However, relevant information on coastal reclaimed tideland (RTL) soils, which are classified as primary salt-affected soils developed through salt-accumulated sediments is lacking. In this paper, we reviewed the physical and chemical properties of RTL soils in comparison with non-RTL soils and analyzed the relationship between rice production and soil salinity in RTL to suggest agricultural management practices for sustainable rice production and soil carbon sequestration in RTL. Similar to the secondary salt-affected soils, RTL soils were characterized by high alkalinity, salinity, and sodicity, and rice yield was negatively correlated with salinity. However, it was also found that lower fertility (e.g., organic matter and phosphorus) of RTL soils than non-RTL soils might also hamper rice growth and thus carbon input via plant residues in RTL soils. Correlation between years after reclamation and soil properties of RTL showed that cultivation of rice with annual fertilization and organic matter inputs increased soil fertility but salinity and sodicity did not show a significant tendency of change, suggesting that natural desalinization in RTL soils is hard to be achieved with conventional rice cultivation. Therefore, it is suggested that fertilization management as well as salinity management via drainage, gypsum application, tillage, and proper irrigation may be necessary to improve rice production and carbon sequestration in RTL soils.     

Household level tree planting and its implications for environmental management in the northwestern highlands of Ethiopia: a case study in the Chemoga watershed,Blue Nile basin

The unsustainable exploitation and destruction of forests is a serious environmental concern in the developing countries of Africa. One of its main driving forces is the growing population causing a growing demand for fuelwood. In Ethiopia, as in many developing countries, there is a heavy dependence on and a growing demand for fuelwood. This dependence has been contributing to a widescale deforestation, as stated in various reports. Contrary to these reports, a study in the Chemoga watershed found a slightly increased forest cover during the past four decades, which was ascribed to households' tree planting practices. The objective of this study was to examine household level tree planting activities in reference to biofuel consumption patterns in four sample villages in the watershed. The results indicate that fuelwood and cattle dung accounted for nearly 100 per cent of the domestic energy consumption, with cattle dung contributing 34 per cent of the total. Fuelwood and dung combined, per capita biofuel consumption was estimated at 511 kg yr⁻¹, but with variations between the villages and socio‐economic groups. Supply appears to have influenced the quantity of biofuels used. The scarcity of wood for fuel and other uses has forced households to plant trees. This has contributed to the increased forest cover of the watershed at the present as compared to that four decades ago. Number of trees planted showed variation between the villages and socio‐economic groups, which is attributable to physical and human factors. In promoting tree planting, agroforesters and environmental management planners should therefore take into account local level biophysical and socio‐economic realities. This agroforestry practice is a good short‐term solution to the problem of fuelwood shortage, and also has many positive implications for environmental management and agricultural production. Thus, it has to be encouraged. Spatially aggregated, local level agroforestry practices contribute positively towards global ecosystem health. Copyright © 2003 John Wiley & Sons, Ltd.     

Effect of Planting Method on the Growth of Alnus glutinosa and Quercus petraea in Compacted Opencast Coal‐Mine Spoils,South Wales

Land degradation on officially ‘reclaimed’ opencast coal‐mine sites is a widespread problem in South Wales. This project explores methods suitable for use by community volunteers seeking to effect local environmental improvement by restoring geoecological self‐sustainability on lands that are commonly affected by extreme auto‐compaction and low soil nutrient status. This paper describes a formally established 7‐year experiment designed to assess the effect of three alternative tree planting strategies used in the forestation of such lands. These are notch planting (e.g. forestry), pit planting (e.g. parks and gardens) and trench planting (e.g. orchard terraces). The study explores tree survival and growth for two species commonly used in land reclamation contexts: alder [Alnus glutinosa (L.) Gaertn] and Welsh or Durmast Oak [Quercus petraea (Matt.) Liebl]. t‐testing of the results shows that survival and growth rates for both species tend to be significantly better for trench planting than for pit planting than for notch planting. Differences in mortality between pit‐planted and trench‐planted trees become less significant during the experiment while differences in growth increase with time. The conclusion is that providing a loosened, lower density, rooting substrate significantly improves both the growth and the survival rates of trees planted in compacted Welsh surface coal‐mine spoils and that trench planting is more effective than parks and gardens‐style pit planting, which is more effective than forestry‐style notch planting. Copyright © 2013 John Wiley & Sons, Ltd.     

Amelioration of calcareous saline sodic soils through phytoremediation and chemical strategies

Abstract. The worldwide occurrence of saline sodic and sodic soils on more than half a billion hectares warrants attention for their efficient, inexpensive and environmentally acceptable management. These soils can be ameliorated by providing a source of calcium (Ca²⁺) to replace excess sodium (Na⁺) from the cation exchange sites. Although chemical amendments have long been used to ameliorate such soils, the chemical process has become costly during the last two decades in several developing countries. As a low‐cost and environmentally acceptable strategy, the cultivation of certain salt tolerant forage species on calcareous sodic and saline sodic soils, i.e. phytoremediation, has gained interest among scientists and farmers in recent years. In a field study conducted at three calcareous saline sodic sites (pH_s=8.1–8.8, EC_e=7.8–12.5 dS m^–1, SAR=30.6–76.1) in the Indus Plains of Pakistan, we compared chemical and phytoremediation methods. There were four treatments; two involved plants: Kallar grass (Leptochloa fusca (L.) Kunth), and sesbania (Sesbania bispinosa (Jacq.) W. Wight). The other two treatments were uncropped: soil application of gypsum and an untreated control. All treatments were irrigated with canal water (EC=0.22–0.28 dS m^–1). The plant species were grown for one season (5–6 months). Sesbania produced more forage yield (34 t ha^–1) than Kallar grass (23 t ha^–1). Phytoremediation and chemical treatments resulted in similar decreases in soil salinity and sodicity, indicating that phytoremediation may replace or supplement the more costly chemical approach. The soil amelioration potential of sesbania was similar to that of the Kallar grass, which suggests that moderately saline sodic calcareous soils can be improved by growing a forage legume with market value.     

Production of the forage halophyte Atriplex amnicola in metal‐contaminated soils

Clean‐up of contaminated soils is a costly and slow process that requires long periods of time to be effective. Therefore, direct use of contaminated sites with appropriate management is often likely to be a more efficient use of such land. Consequently, the production of safe animal forages from contaminated soils was the aim of this research. Field studies were conducted to evaluate the growth and elemental composition of river saltbush (Atriplex amnicola) grown on a metal‐contaminated soil. The soil was amended with compost at rates of 0, 15 and 30 t/ha to assess its role on plant growth and metal uptake. Compost application significantly (P < 0.05) increased biomass yield, crude protein (CP) and ash content of river saltbush; in contrast, it decreased the Zn and Pb concentrations in shoot tissues. When 30 t/ha of compost was added, the Pb concentrations in the stems and leaves decreased by 32 and 38%, respectively. Despite the large total and extractable content of metals in the studied soil, shoot concentrations of these metals in A. amnicola were always maintained below potentially toxic levels. The biomass material of A. amnicola had a high nutritive value compared to conventional forage crops and could safely be used as animal forage. This work demonstrates that an Atriplex spp, A. amnicola, has significant potential for use as a safe forage crop in the sustainable on‐site management of contaminated soils.     

Effect of Biosolids and Cd/Pb Interaction on the Growth and Cd Accumulation of Brassica rapa Grown in Cd-Contaminated Soils

Mixed metals in the cropped lands in central Taiwan contaminated about 230 ha. According to the Soil and Groundwater Protection Remediation Act (SGWR Act) of Taiwan, these lands were restored. However, some grains of paddy rice grown in these remediated soils still contained more than 0.5 mg Cd kg^?1, which the Department of Health of Taiwan notified as the maximum allowable Cd content in rice. The suitability of planting edible crops in these soils is now in doubt. Brassica rapa is the crop most often sold in Taiwan's market and is planted in the interval between the first and second stages of planting of paddy rice, especially in central Taiwan where this experiment was conducted. A pot experiment was conducted using soils contaminated artificially with Cd or both Cd and Pb. The soil was then amended with 5% of biosolid and followed by planting of B. rapa. The objectives were to study the effect of biosolid amendment on the soil and the interaction between Cd and Pb on the growth of and Cd accumulation in B. rapa. Experimental result showed that the biomass and the accumulation of Cd by B. rapa were significantly increased in the biosolid-amended soils compared with the control. Lead has a synergistic effect on enhancing the accumulation of Cd by B. rapa grown in artificially Cd-contaminated soils.     

Growth of perennial forage legumes in acidic soils of the Appalachian Hill‐Lands after liming

A major constraint to the renovation of forage legume‐based pastures on acidic soils of the Appalachian hill‐lands is thought to be the absence of effective rhizobia. A growth chamber experiment was done with aluminum (Al) toxic, low pH (≥ 4.2) soils from four series (Berks, Lily, Tate, and Westmoreland) that were planted with alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), white clover (Trifolium repens L.), or birdsfoot trefoil (Lotus corniculatus L.). These soils, without lime addition, were previously shown not to contain effective, naturalized populations of rhizobia for these plant species. However, a non‐toxic, pH 6.8, Watauga soil was shown to have such rhizobia but only for alfalfa. In the present study, these five soils were reexamined after liming to pH ≥ 5.5 for effective, naturalized populations of rhizobia and the efficacy of soil inoculation with commercially available rhizobia. In addition to effective, naturalized R. meliloti for alfalfa in the Watauga soil, similar populations of R. trifolii for red clover, and R. lotus for birdsfoot trefoil, were now found. Such rhizobia were also found for alfalfa in the Lily soil and for red clover in the Lily and Tate soil. Thus, liming allowed the expression of effectiveness of natural rhizobia that otherwise would not have been detected in soil pot experiments without lime. Inoculation of the toxic soils after lime addition with commercial rhizobia was effective in about half of the soil‐plant combinations that did not contain populations of effective, naturalized rhizobia. Asymbiotic shoot growth of all the plant species was significantly (P ≤ 0.05) correlated with soil pH over a range of 5.5–6.6. These results indicate that, in the absence of effective, naturalized populations of rhizobia, improvement of rhizobial inocula could increase forage production by ～34% for some species on some of the toxic soils, even after the pH of the soils is increased to ≥ 5.5.     

水旱轮作与林地利用方式对中国滨海滩涂土壤微生物生物量碳的影响

Rice-wheat rotation and poplar afforestation are two typical land use types in the coastal reclaimed flatlands of eastern China.This study investigated two rice-wheat rotation lands(one reclaimed from 1995 to 2004 and cultivated since 2005, RW1, and the other reclaimed from 1975 to 1995 and cultivated since 1996, RW2) and a poplar woodland(reclaimed from 1995 to 2004 and planted in2004, PW1) to determine the effects of land use types and years of cultivation on soil microbial biomass and mineralizable carbon(C) in this coastal salt-affected region. The results showed that the soil in PW1 remained highly salinized, whereas desalinization was observed in RW1. The total organic C(TOC) in the top soil of PW1 and RW1 did not show significant differences, whereas at a soil depth of 20–30 cm, the TOC of RW1 was approximately 40%–67% higher than that of PW1. The TOC of 0–30-cm soil in RW2 was approximately 37% higher than that in RW1. Microbial biomass C(MBC) and mineralizable C(MNC) exhibited the trend of RW2 RW1 PW1. Sufficient nutrition with more abundant C substrates resulted in higher MBC and MNC, and soil respiration rates were negatively correlated with C/N in RW1 and RW2. Nutrient deficiency and high salinity played key roles in limiting MBC in PW1. These suggested that rice-wheat rotation was more beneficial than poplar afforestation for C accumulation and microbial biomass growth in the coastal salt-affected soils.     

苏北海涂围垦区土壤质量综合评价研究

以苏北海涂围垦区为研究区域,选取与作物生长密切相关的理化性质作为评价指标,分别采用相关分析法与主成分分析法确定权重系数,并应用综合指数法对土壤质量进行定量评价,获取区域土壤质量综合评价分级图.结果表明:围垦区土壤质量状况总体较差,存在一定程度盐渍化危害,土壤有机质和氮素含量偏低,碱解氮亏缺尤为严重.有机质是重要的土壤质量评价因子,土壤盐分与地下水矿化度是土壤质量的主要限制因子.相关分析法和主成分分析法对土壤质量的评价结果较为一致,r2 = 0.933 9**.围垦区不同部位土壤质量差异较大,围垦区西部棉花地土壤质量总体优于东部水稻地,且不同评价方法得到的土壤质量分级图具有空间相似性.该结果可为滩涂区中、低产地的精确施肥、障碍土壤的科学管理提供参考依据.     

洼涝盐渍土“淡化肥沃层”的培育与功能的研究

本文通过１９８６－１９９３年微区及大田试验说明,对洼涝盐渍土采用不同培肥措施,培育“淡化肥沃层”,改善了土壤理化生物状况,提高了土壤肥力。因此,在不减少土体盐贮量的条件下,以“肥”调控水盐,把盐分调节在土壤表层４０ｃｍ根系活动层以下,在作物主要根系活动层创造一个良好的肥水盐生态环境,以利实现高产。     

Interaction of tree crops with a sodic soil environment: potential for rehabilitation of degraded environments

Tree species of Acacia nilotica, Dalbergia sissoo, Prosopis juliflora and Terminalia arjuna were grown on sodic land for a decade at the Biomass Research Centre, Banthra (of National Botanical Research Institute, Lucknow) India (80°45′–53′E and 26°40′–45′N) with the objective of discovering their relationship with the sodic soil environment to rehabilitate it for maximum fuelwood production. Results showed a marked improvement in biogeochemical characteristics of soil by increasing the water holding capacity (WHC), and by the addition of organic carbon, nutrients and fungal microflora. It was found that D. sissoo and P. juliflora were more efficient than were A. nilotica and T. arjuna in rehabilitating the land. Litter production by the first two was greater than that provided by A. nilotica and T. arjuna, which subsequently caused depletion in soil pH and exchangeable sodium percentage (ESP) values. It was found that there was a greater circulation of Ca, Mg and Fe than the other nutrients by all four tree species, which was a desirable factor. Microbial activity was enhanced due to the accumulation of humus through decomposition of leaf litter and root decay. The potential extent of the biological rejuvenation of the sodic land was related to the distribution of tree roots in the soil profile. To obtain better results a combination of such tree species should be selected in order to provide maximum and constant litter mulch throughout the year. This, in turn, would protect the land from desiccation. Thus, sodic lands could be rehabilitated effectively to restore degraded environments through appropriate mixed tree cropping systems. © 1998 John Wiley & Sons, Ltd.     

Leguminous trees for the restoration of degraded sodic wasteland in eastern Uttar Pradesh,India

The study was carried out in sodic lands of Sultanpur District, Uttar Pradesh, India. The barren soils and the soils supporting 3‐, 6‐ and 9‐year‐old plantations of Prosopis juliflora (Swartz) D.C. and Dalbergia sissoo Roxb. Ex. D.C. plantations were examined to assess the rate and extent of changes undergone by physical and chemical properties of the soil. The study brought out that these species indicated the process of soil rehabilitation from the early stages of growth and the extent of rehabilitation increased with the age of the plantation. P. juliflora was found to be more efficient in reclaiming the soil in comparison to D. sissoo. The decline in soil pH and exchangeable sodium percentage (ESP) indicates the desodification and enrichment with organic C, N, P and K indicates improvement in nutrient status of the soil. After 9 years of planting the surface soil was completely desodified as indicated by pH (<8ċ5), ESP (<15) and sodium adsorption ration (<15). A significant increase in organic C, exchangeable Ca²⁺ and Mg²⁺ and decrease in exchangeable Na⁺ reveals that the nutrient status is attaining suitable balance. The physical attributes of the soil also underwent improvement in terms of increase in porosity, water‐holding capacity, field capacity and decline in bulk density. The flocculation of dispersed soil surface and improvement in soil structure was indicated by increased infiltration rate (cm h⁻¹) and soil permeability (cm²). Copyright © 2003 John Wiley & Sons, Ltd.