Soil Moisture Retention Capacity Research Articles

Agronomic performance of soybean and sorghum in a short rotation poplar coppice alley-cropping system under Mediterranean conditions

The transition from conventional arable towards silvoarable systems can increase the delivery of ecosystem services. Nevertheless, the assessment of crop yield under agroforestry condition is crucial to evaluate of the reliability of these systems and to increase the knowledge base needed to support their design. Although the feasibility of poplar short rotation coppice (SRC) silvoarable alley-cropping systems has been widely investigated, few studies have addressed the agronomic response of crops intercropped with poplar SRC in narrow alleys, especially in Mediterranean environments. Thus, this paper treats the effects of SRC poplar rows on soybean and sorghum productivity in a 2-year rotation implemented in an alley-cropping system. A field experiment was carried out in 2018 and 2019 with the objective of measuring and evaluating effects of light availability variation, as affected by the growing rate of 2-year coppice cycle poplar SRC rows, and the soil characteristics on soybean-sorghum and sorghum–soybean rotations. Above-ground biomass, grain yield and crops residue showed a significant reduction in the tree–crop interface up to 74% and sorghum proved to be less tolerant to light reduction compared to soybean. Our results demonstrated that light is the most important factor for sorghum cultivation, despite grain yield was also influenced by the soil characteristics such as pH, while soybean is affected also by soil moisture and water retention capacity. The design of crop rotation in an SRC-based agroforestry system needs to consider the different agronomic performance of different crops and the harvest cycle of tree rows.

Evaluation of the Effectiveness of Loose and Compressed Wood Chip Mulch in Field-Grown Blueberries—A Preliminary Study

Blueberry production in the field faces several challenges, including competition from weeds and soil suitability. Different mulch types are widely used in blueberry cultivation to control weeds, conserve moisture, and mitigate soil erosion. However, the comparative effects of loose and compressed wood chips on fruit quality and weed control in blueberry production systems have not been studied. Many farmers use expensive imported peat moss as soil covers, while others apply organic mulches such as chips or chaff, which can be easily washed away by runoff. This study aimed to evaluate the effects of compressed mulching boards (MB) fabricated without the use of chemical adhesives using pressurized steam and compression technologies in blueberry cultivation. During the two growing seasons, the effectiveness of compressed MB on soil moisture retention, fruit quality, and weed biomass was compared to that of wood chip (WC) and control treatments in a blueberry field. Although a significant difference was observed in the fruit fresh weight, no significant differences were observed in the other fruit growth parameters for all the treatments. Generally, the compressed MB significantly improved soil moisture retention capacity compared to WC and control during the two-year study. The compressed MB showed effective weed suppression ability by significantly reducing the weed biomass at all sampling times.

Comparative Analysis on Impact of Different Mulches on Growth and Yield Parameters of Mulberry under Rainfed Condition of Poonch District of Jammu and Kashmir

The current study was formulated to analyse the impact of different biodegradable and synthetic mulches on growth and yield parameters of mulberry plant. Among the selected parameters survival rate of mulberry plants was recorded to be maximum in T-2 i.e, paddy straw and husk as 95% followed by T-1 and T-3 i.e, Black polythene mulch and Green branches of tree respectively as 90% and least for Control i.e, without any mulch as 70%. Least population of weeds with minimum intensity was recorded in T-1 (05) followed by T-2 (08) and T-3 (10). Maximum weed flora with highest intensity of weeds was found in Control i.e, without any mulch (20). For the studied samples, maximum soil moisture percentage and moisture retention capacity (MRC) of 66.57 & 95.6% was recorded in T-1 followed by T-3 as 40.31 & 87% and T-2 as 16.36 & 91% and minimum in control as 13.43 & 85.56%. The pH was recorded as 6.1 in T-1 depicting the slightly acidic soiland could be viewed as the most appropriate soil pH for mulberry cultivation. Available NPK were recorded to be in the most ideal range for T-1 as 8.2, 1.3 and 9.6%. Maximum leaf size was recorded in T-1 as 126cm followed by T-2 and T-3 as 116cm and 110cm respectively and 105cm in control. Moisture percentage was recorded to be highest 76.23% followed by 74.61% and 54.16% for T-3, T-1 and T-2 respectively and 68.2% in control. Maximum MRC was observed in case of plants grown under Black polythene mulch (73.24%) and least in green branch mulch (61.39%). Therefore, it can be concluded that application of suitable bio-mulches in mulberry fields can reduce the dependency of chemical weedicides.

Surface runoff estimation using geographic information system and soil conservation service-curve number method for sub catchments of Karamadai, Tamil Nadu

Water conservation becomes essential as the resource becomes scarcer. The most important step in managing water resources is estimating watershed runoff generated from rainfall, as the runoff and rainfall are the key factors in determining water availability for surface storage and groundwater recharge. So, this study is mainly focused on estimating the surface runoff generated from the three sub-catchments of Karamadai, Tamil Nadu, India, using the heavy to extreme daily rainfall events received in the study area within the span of 20 years (2000–2019). The study was performed in the ArcGIS environment using remote sensing data. The SCSCN (Soil Conservation Service-Curve Number) method was used to estimate surface runoff. The changes in the land use in each sub-catchment were analysed in each decade and studied for their impact on the runoff depth. The land use and land cover classification map of the study area was prepared from LISS III satellite imagery for the years 2006 and 2016 by using supervised classification. The curve number was assigned based on land use as well as the hydrologic soil group. The weighted curve number was calculated from the area under each land use and then used to calculate storm runoff. The maximum runoff occurred in 2011 in all the catchments of the Karamadai block. It was found that more runoff occurred in the Mandrai Pallam catchment compared to Periya Pallam and Pare Pallam, as the Mandrai Pallam catchment had less soil moisture retention capacity than the other two catchments. So, more priority must be given to this catchment while planning to implement the soil and water conservation measures.

Pyrolysis of rice husk using CO2 for enhanced energy production and soil amendment

Anthropogenic CO2 generations from use of fossil resources has led to catastrophic climate problems. Biochar is a promising material for CO2 capture and storage in soil, because it does not require additional storage space. To produce biochar, pyrolysis is required in an oxygen-limited condition. In an attempt to offer more environmentally benign route for biochar formation, this study introduced CO2 as a reaction agent. Using rice husk as a model compound, biochars were produced under CO2 and N2 condition. Porosity of rice husk biochars (RHBs) were enhanced under CO2 condition, because CO2 affected to formation of nano-sized pores. pH and moisture retention capacity of garden soil was controlled with an addition of RHBs. Mixtures of garden soil and RHB were also used as cultivation media for growth of barley grass, and plant growth in the mixtures was improved by 20% comparing to garden soil. Moreover, CO2 contributed to enhanced syngas generation during biochar production through gas phase reactions between CO2 and volatile compounds. Thus, this study proved that CO2 is a useful reactant for pyrolysis of biomass waste.

Assessing the influence of immobilization remediation of heavy metal contaminated farmland on the physical properties of soil

The potential for negative effects of heavy metal remediation on the ecological environment of soil is an issue of widespread concern. As a basic index of soil moisture and fertility retention capacity, the response of the physical properties of soil to immobilization remediation is therefore extremely important and is the main focus of this study on remediated farmland in the mining area of Tangshi village, Henan province, China. Accordingly, topsoil samples and ring knife samples were collected from five separate farmland plots, four of which had been remediated with the respective soil amendments of 1) nano silica; 2) silicate, phosphate and clay minerals; 3) biochar and organic fertilizer; and 4) biochar and phosphate; whilst for experimental control purposes the 5th plot had no remediation measures. The physical properties of particle composition, bulk density, porosity and aggregate were subsequently determined. The results show that nano silica tends to refine the soil, mainly by significantly reducing the content of sand and increasing the content of silt and clay, but did not change the soil texture type. Furthermore, nano silica can promote the formation of soil macro-aggregates and reduce the content of micro-aggregates. However, the other three amendment compositions show no significant effect on soil particle composition and aggregate content. On the whole, the amendments of the four remediation plots can significantly reduce soil bulk density and increase porosity, thus facilitating soil changes that are more beneficial for crop growth. The results, therefore, go some way into alleviating the concerns surrounding heavy metal remediation and damage to the ecological environment of soil.

Development of natural fiber-based degradable nonwoven mulch from recyclable mill waste

The extensively used agricultural polyethylene mulch is associated with serious environmental pollution because it is difficult to degrade. This study evaluated the feasibility and degradability of a new mulch that was fabricated entirely from recyclable biodegradable natural fibers. In 2018, three types of this new natural fiber-based mulch were prepared from textile mill waste using needle-punched nonwoven technology and characterized using both laboratory and field tests. Physical parameters, including air permeability, thermal insulation value, and light transmittance, were determined through laboratory tests. Other parameters, including soil moisture content, soil temperature, weed suppression, agronomic traits, cotton yield, and soil burial degradation, were investigated through field tests, with a degradable plastic film as the control. The results showed that the crop yield from the best new mulch treatment (2802.2 kg/arc) and the degradable plastic film treatment (2851.3 kg/arc) were similar. The superior thermal insulation value of the new mulch, which was at least 9.4% higher than the control, facilitated its capacity to substantially moderate soil temperature. The weed germination suppression ratio of the new mulch was 50% higher than the control because it was 100- fold thicker and showed 54.6% lower light transmittance. In addition, after 90 days in the soil, the new mulch evidently degraded. Therefore, this newly developed degradable nonwoven mulch addresses the issue of industrial waste utilization, thereby preventing agricultural pollution. In the future, enhancing the soil moisture retention capacity of the new mulch will greatly facilitate its application.

Soil moisture retention on slopes under different agricultural land uses in hilly regions of Southern Transdanubia

Increasingly severe weather extremes are predicted as one of the consequences of climate change. According to climatic models, weather extremities induce higher risks for both flood and drought in the Carpathian Basin. Throughout the 19th and 20th centuries, flood control relied on cost-intensive engineering structures, but recently ecological solutions have come to the fore. Flood hazard on major rivers could be mitigated if multiple and cumulative water retention opportunities are exploited on the upper sections of tributary catchments. Appropriate land use and landscape pattern changes can shift the infiltration to run-off ratio to the benefit of the former. In the Transdanubian Hills of Southwest Hungary three study areas with different agricultural land use types had been selected and investigated for the impact of landscape micro-features on soil moisture retention capacity with the purpose of conserving water from wet periods for the times of drought. Marked differences in moisture dynamics have been detected between arable land, grasslands and orchards. This fact underlines the need for integrated soil and water conservation. Drought risk was found to be the highest on ploughland. Favourable soil water budgets have been observed in the fields as a function of land use: less intensive types, like grazing land and orchards (particularly tree rows), were identified as places of high water retention capacity. Although serious water stress conditions were also reached in the orchard, it markedly mitigated drought conditions compared to the ploughland.

Plant Available Water Capacity (PAWC) for Deep-Rooted Crops in Cracking Clay Soils (Vertisols) of Semi-Arid Central India

Smectite is the dominant clay mineral in the cracking clay soils (mainly Vertisols) in the semi-arid tropical (SAT) region (Vidarbha andMarathwada).Amongst the crystalline clay minerals, smectite has the highest soil moisture retention capacity depicted as the available water between field capacity and wilting point, which increases with soil depth. But in SAT Vertisols of Vidarbha and Marathwada regions, the release of this soil water is unavailable to deep-rooted crops, causing loss of crop yield is frequently observed. Thus, the water holding between33 and 1500 kPa tension is not in reality available soil moisture in these soils. The release of soil moisture is, however, seriously constrained by the dispersion of smectitic clay colloids due to the presence of both Mg and Na ions on soil exchange complex. In reality, in calcareous Vertisols of non-sodic nature, soil moisture is held at 100 kPa while in calcareous Vertisols of sodic nature it is held at 300 kPa. Based on this field observation the concept of plant available water content, which relates to profile water content, was adopted earlier to calculate the plant available water capacity (PAWC) considering the soil moisture held between 100-1500 kPa for non-sodic and 300-1500 kPa for sodic soils. This pragmatic PA WC method showed a significant positive correlation between the PA WC and the yield of cotton (lint + seed) of 32 Vertisols of the Vidarbha region, however, it did not address the status of soil moisture release at higher tensions. It is apprehended that at higher tensions, the release of soil moisture is not enough during the dry period of the season that can prevent the extension of vertical cracks in the slickensided horizons at deeper depth of 100 cm and beyond. Less amount of soil water in the subsoils is due to the decrease of saturated hydraulic conductivity(sHC) with depth preventing the free flow of rainwater in the subsoils. This makes subsoils as more water constraint horizons but enriches subsoils with pH > 8.0, more amount of Mg2+ and Na+ ions on soil exchange complex. Such Vertisols do not support the second crop during the winter months. In view of this predicament in agricultural land use plan of SAT Vertisols, the present study was undertaken to understand the cause and effect relationship between soil moisture and relevant soil parameters that prevent the release of soil moisture at higher tensions. In order to find an insight into this queer issue, soil moisture retention and release curves at 33, 100, 300, 500, 800, 1000 and 1500 kPa, were obtained for each genetic horizon of 33 representative Vertisols ofVidarbha andMarathwada region. In Vidarbha, Vertisols are Aridic/Typic/Sodic Haplusterts and Calciusterts, and in Marathwada, they are Typic/Sodic Haplusterts. Moisture tension curves indicate that the release of water beyond 800 kPa is negligible. Failure in the release of soil water beyond 800 kPa is due to the dispersion of fine clay size smectite (< 200 nm) consisting primarily of nano-size smectite (<100 nm), caused by the Mg2+ and Na+ ions present on the soil exchange complex. The dispersed nano-size smectite blocks the macropores and simultaneously increase the micropores, where soil moisture is held very tightly. In the present study, PA WC calculation was done considering the soil water held between 100-800 kPa for soils of non-sodic nature, and for sodic soils, it was between 300-800 kPa. The revised PAWC data showed a better significant positive correlation with yields of cotton on farmers ’field, in comparison to correlation obtained earlier. Thus, it stands as a robust index parameter of soil abiotic stress in SAT environment. This unique parameter having a legacy to major pedogenetic processes in SAT Vertisols. In Indian states under SAT, PAWC emerges as a formidable biophysical parameter for evaluation of rain-fed Vertisols for growing deep-rooted crops.

Effects of Compost Manure on Soil Microbial Respiration, Plant-Available-Water, Peanut (Arachis hypogaea L.) Yield and Pre-Harvest Aflatoxin Contamination

ABSTRACT Peanut production in Zambia is often characterized by low yields and high aflatoxin incidence in harvested kernels. Soil amendments such as farmyard manure have shown potential to increase yields and reduce pre-harvest aflatoxin incidence. The aim of the current study was to evaluate the effects of composted cattle manure on soil properties that relate to yield and pre-harvest aflatoxin contamination of peanut kernels. Research evaluated the effects of composted cattle manure on soil respiration, plant-available water (PAW), peanut yield and pre-harvest aflatoxin contamination in a field experiment conducted in two successive rain-fed cropping seasons starting in December, 2015 and ending in April 2017, in Chongwe District, Zambia. Six (6) levels of compost were incorporated into the top 10 cm of the soil at rates of 0, 4.5, 12.0, 19.5, 27.0, and 34.5 metric tons/ha 1 wk before planting. There was a strong positive relationship between levels of compost and soil microbial respiration (R2=0.84) and PAW (R2=0.86). Secondly, compost manure was associated with increases in pod (R2=0.65) and kernel (R2=0.61) yield. The kernel yield potential of the planted cultivar was achieved at the rate of 12 metric tons per ha. Thirdly, there was a reduction in total aflatoxin levels with increasing levels of compost (R2=0.85). The improvement in peanut yield and the decrease in aflatoxin concentrations in kernels can be attributed to the improvement in soil moisture retention capacity and soil microbial activity arising from manure amendments. This study demonstrated the potential of compost manure to increase soil microbial activity, PAW, peanut yield and minimize aflatoxin contamination at field level.

Incorporating Influences of Shallow Groundwater Conditions in Curve Number-Based Runoff Estimation Methods

Runoff generation process in any watershed is mainly affected by precipitation, land use and land cover, existing soil moisture conditions and losses. Shallow groundwater table conditions that occur in many regions are known to affect the soil moisture retention capacity, infiltration and ultimately the runoff. A methodology that links soil moisture capacity to the shallow groundwater table or High-Water Table (HWT) using a nonlinear functional relationship within a curve number (CN)-based runoff estimation method, is proposed and investigated using single and continuous event simulation models in this study. The relationship is used to obtain an adjusted CN that incorporates the effect of change in soil moisture conditions due to HWT. The CN defined for average conditions is replaced by this adjusted CN and is used for runoff estimation. A single event model that uses Soil Conservation Service (SCS) CN approach is used for evaluation of variations in runoff depths and peak discharges based on different HWT conditions. A real-life case study from central Florida region in the USA was adopted for application and evaluation of the proposed methodology. Results from the case study application of the models indicate that HWT conditions significantly influence the magnitudes of peak discharge by as much as 43% and runoff depth by 48% as the water table height reaches the land surface. The magnitudes of increases in peak discharges are specific to case study region and are dependent on the functional form of the relationship linking HWT and soil storage capacity. Also, for specific values of HWT, an equivalency between HWT-based CN and wet antecedent moisture condition (AMC)-based CN can be established.

Derivation of Soil Moisture Recovery Relation Using Soil Conservation Service (SCS) Curve Number Method

Soil moisture retention (SMR) capacity plays a key role in estimating the direct runoff when a multi-pulse storm event occurs. It is very important to know how much SMR will be recovered during the intervals of no rain of a multi-pulse storm. This study developed a new approach for derivation of the SMR recovery curve (R-curve) at sub-daily time-scales using the Curve Number (CN) method. The methodology was applied using complex storm events in the Napa River basin, California. The R-curve is classified into three sections depending on the recovery rate of SMR during the inter-storm interval of no rain (INR), and this study defines the characteristics. The first section of the R-curve (INR 0–21 h with 0.97 mm/h) is described as gradually recovering SMR, since water is being infiltrated and the upper soil layer is not fully saturated. The second section (INR 21–36 h with 2.11 mm/h) is defined as steeply recovering S due to downward drainage (sub-surface/inter flows) and evaporation without infiltration. The third section (INR 36–68 h with 0.34 mm/h) is described as gradually decreasing recovery dependent on evaporation since percolation and drainage have almost stopped.

Efficacy of open weave jute geotextiles in controlling soil erosion and its impact on hill slope stabilization

Slope stabilization is a tedious process since various human activities being carried out in various parts of theworld have led to land use changes that has indirectly affected slope stability. Permanent structures are being usedfor slope stabilization which are costly and cannot be adopted in a large scale. Slope stabilization by establishinggrasses with the support of Jute Geotextiles is an alternative method for stabilization of slopes in hilly areas. Set offield studies were conducted at ICAR- Indian Institute of Soil and Water Conservation (IISWC), Regional Centre,Udhagamandalam, Tamil Nadu, India with the objective to study the effect of various Jute Geotextiles (JGT) on runoff, soil loss, survival and growth of tea. Results of three years field study on efficacy of various types of open weave JGT namely 500, 600 and 700 GSM on slope stabilization showed that 700 GSM open weave JGT proved to be more effective in reducing runoff, soil and nutrient loss and increased soil moisture retention capacity of the soil. However, height and growth of tea plants were better under 500 and 600 GSM JGT. Considering the scope of tea cultivation in sloppy areas, rehabilitation of land slide areas using tea plants, optimal moisture requirement and better growth of tea plants, it is suggested that 500 GSM open weave JGT will be more effective for slope stabilization with tea plants.

Impact of soil cover systems on soil quality and organic production of yacon

Abstract The use of soil cover in vegetables is a widespread practice that provides innumerable advantages to the soil and crop. The objective of this study was to evaluate the soil attributes and the organic production of yacon in different soil cover systems in the Atlantic Forest Biome, Brazil. The experiment was conducted in a randomised complete block design with five replicates. The treatments consisted of seven soil covers: two covers with plastic film, one black and one two-sided white/black, with the white surface facing the atmosphere; a cover with corn straw (30 Mg ha−1); three covers with different levels of coffee husk (1 = 37.5 Mg ha−1; 2 = 75.00 Mg ha−1; and 3 = 112.50 Mg ha−1); and a treatment with no soil cover (NC). During the crop growth cycle, data and soil samples (0–5 cm) were collected monthly, and the following were evaluated: total organic carbon, total nitrogen, potentially mineralisable nitrogen, microbial biomass carbon, C-CO2 emissions, temperature, moisture, metabolic quotient, and microbial quotient. The dry mass of the spontaneous vegetation was determined at 60, 100, 140, 180, and 210 days after yacon planting. At the end of the growth cycle (210 days after planting), the yield of yacon tuberous roots and the net carbon balance were evaluated. Independent of the cover material, the soil cover systems led to greater stability of soil microbial activity and CO2 emissions, in addition to greater immobilisation of C in the microbial biomass, promoting a positive C balance in the soil covered with corn straw (10.99 Mg ha −1) and coffee husk at levels 1 (12.88 Mg ha−1), 2 (28.12 Mg ha−1), and 3 (43.28 Mg ha−1). The soil cover reduced temperatures (mean of 6.43%) and greater soil moisture retention capacity (mean of 35%), with the black plastic film being the least efficient. Additionally, the soil covers suppressed spontaneous vegetation, especially the plastic films (100% suppression) and coffee husk at levels 2 (50% suppression) and 3 (74% suppression). These benefits led to higher yields of yacon tuberous roots, most notably the double-sided plastic film cover (31.71 Mg ha−1) and coffee husk at level 2 (28.35 Mg ha−1).

Impact of Neem-coated Urea on Production, Productivity and Soil Health in Punjab

The present study was undertaken to analyze the trends in usage and prices of urea in Punjab, to analyze the adoption behavior of neem coated urea (NCU) among selected farmers, to analyze the impact of adoption of NCU on crop productivity and farmers ’income and to suggest suitable policy measures for adoption of NCU. The data were collected from randomly selected 200 farmers from four blocks of Ludhiana and Patiala districts where paddy is a major kharif crop which requires adequate doses of urea for its growth. The results of the study revealed that the consumption/sale of urea in Punjab during the year 2007–08 was 2646.44 th. MT which rose to 3086.05 th. MT during the period 2007–08 to 2015–16 at an annual growth rate of 1.64 percent. The urea prices increased significantly at the highest growth of 5.21 percent per annum during the decade 1990–91 to 1999–2000 while during the period 1980–81 to 2015–16 the growth in urea prices was 3.33 percent per annum. The analysis of the primary data revealed that the majority of the respondent farmers purchased NCU and Normal urea (NU) from co-operative societies followed by private fertilizer dealers while the cost per bag of NCU, including transportation cost, worked out to be 289.69 while it was 276.58 per bag in case of NU. There was marginal increase in the productivity of paddy crop during the year 2015–16 as compared to the year 2014–15. The net returns per acre were estimated to be 31401 during the year 2015–16 and 29530 in 2014–15. As far as awareness about NCU was concerned, almost all the selected farmers were aware about the NCU and major source of awareness was co-operative societies. There was a significant increase in the application of NCU after 2015–16 in crops such as; paddy, wheat, basmati, sugarcane, potato, maize, sunflower, and vegetables. Due to the application of NCU, only 5.29 percent farmers reported about the increase in paddy yield while the cost of pest and disease control declined by 21 percent. There was increase in productivity of paddy crop where neem coated urea (NCU) was applied on the sample farms. Also, the NCU usage on the sample farms increased while cost of pest and disease control measures declined. The partial budgeting technique brought out that there were added returns of 718 per acre by application of NCU on the sample farms. It was also revealed by all the respondents that there was no change in the texture of the soil, soil moisture retention capacity, water infiltration rate, soil softness and decline in the compaction of the soil due to application of NCU but there was higher retention of nitrate in the soil and thereby its slow release to the crop. Also, the NCU usage on the sample farms increased while cost of pest and disease control measures declined. High price of NCU, inadequate/shortage of supply during peak season and poor quality of NCU in some of the co-operative societies were the major problems reported by the respondents. Major suggestions were; assured/timely and adequate supply of NCU to co-operative societies and organizing training camps for spreading awareness. Major policy issue suggested was to lay emphasis on ensuring good quality, adequate quantity and timely supply of NCU along with bringing its price at par with NU.

Application rate and plant species affect the ecological safety of sewage sludge as a landscape soil amendment

Recycling sludge as a soil amendment has become a viable option for sludge disposal. However, such application can lead to soil pollution because of its enrichment in contaminants, especially heavy metals. To identify an effective means to ensure the ecological safety of sewage sludge landscape utilization, a glasshouse experiment was conducted by mixing sewage sludge at 0%, 15%, 30%, 60%, and 100% (V/V) amendment ratios to landscape soils and planting five common landscape plants (Aphelandra ruellia, Syngonium podophyllum, Schefflera odorata, Alocasia macrorrhiza, and Dianella ensifolia). Sludge amendment significantly improved fertility and moisture retention capacity of soil, but dramatically increased the contents of Cd, Pb, Cu, and Zn. Compared with lateritic red soil (CK), sludge amended-soils increased the relative growth rate of landscape plants and enhanced their nutrient uptake and heavy metals accumulation. A rate of 30% or less of sludge application showed positive growth effects for all five landscape plants, and did not cause potential ecological risks of heavy metals to landscape soils. However, rates of 60% or higher posed very high potential ecological risk in multiple metals, particularly in Cd. Interestingly, S. odorata, A. ruellia and A. macrorrhiza could alleviate the ecological risks of Cd, Cu and Zn, respectively, and these results were confirmed by data of relative changes in heavy metal contents in post-experiment soil. Our results suggest that attention to reducing the environmental risks of heavy metals in sludge utilization as landscape soil-amendments should not only be paid to controlling the application dosage of sludge but also to planting suitable plant species.

Multifunctional Environmental Smart Fertilizer Based on l-Aspartic Acid for Sustained Nutrient Release.

Fertilizer is one of the most important elements of modern agriculture. However, conventional fertilizer, when applied to crops, is vulnerable to losses through volatilization, leaching, nitrification, or other means. Such a loss limits crop yields and pollutes the environment. In an effort to enhance nutrient use efficiency and reduce environmental pollution, an environmental smart fertilizer was reported in the current study. Poly(aspartic acid) and a degradable macro-cross-linker based on l-aspartic acid were synthesized and introduced into the fertilizer as a superabsorbent to improve the fertilizer degradability and soil moisture-retention capacity. Sustained release behavior of the fertilizer was achieved in soil. Cumulative release of nitrogen and phosphorus was 79.8% and 64.4% after 30 days, respectively. The water-holding and water-retention capacities of soil with the superabsorbent are obviously higher than those of the control soil without superabsorbent. For the sample of 200 g of soil with 1.5 g of superabsorbent, the water-holding capacity is 81.8%, and the water-retention capacity remains 22.6% after 23 days. All of the current results in this study indicated that the as-prepared fertilizer has a promising application in sustainable modern agriculture.

Improving Nutrient and Water-Holding Capacity in Sandy Regosol by Applying Locally Available Amendments

A pot experiment was carried out at the agronomy farm Eastern University, Chenkalady, Batticaloa, to study the impact of locally available organic manures on the nutrient and water holding capacity of sandy regosol. Three organic sources integrated with different rates of recommended chemical fertilizer and were evaluated with sole recommended chemical fertilizer. Twelve treatments including integrated organic manures with chemical fertilizers at different rates, sole organic manure treatment, sole chemical fertilizer treatment at recommended level and at half the recommended level and no fertilizer control. Completely Randomized Design with 3 replicates was used as layout. Soil analysis for available soil nitrogen content, moisture retention, cation exchange capacity and organic matter content were carried out at planting (red onion), just before top dressing and at the time of harvest. Integration of organic manure with chemical fertilizer favorably influenced nitrogen availability in soil. Among the organic manures poultry manure had the greatest influence on soil available nitrogen : content. Organic manures increased the soil moisture retention capacity, with tank silt (Organic deposit in dry mud) ranking first. Soil cation exchange capacity was favorably influenced by organic manure application. Cation exchange capacity was higher in tank silt treatment than other organic sources. Cation exchange capacily was increased from planting stage to just before top dressing and decreased at harvest stage. The soil organic matter content also followed a similar trend. AGRIEAST 2009 (8) p.30-38

Soil moisture dynamics and restoration of self‐sustaining native vegetation ecosystem on an open‐cut coal mine

Post‐mining landscape reconstruction on open‐cut coal mines aims to support restoration of self‐sustaining native vegetation ecosystems that in perpetuity require no extra inputs relative to unmined analogs. Little is known about the soil moisture retention capacity of the limited layer of topsoil replaced (often &lt;30 cm deep), impacts of deep ripping of the profile, and the combined impacts of these on plant available water during the mine restoration process. We examined changes in soil moisture parameters (soil water potential, Ψ, and soil water content, Θ) daily using automated soil sensors installed at 30 and 45–65 cm depths on mine restoration sites aged between 3 and 22 years and on adjacent remnant vegetation sites following heavy rainfall events at Meandu mine, southeast Queensland, Australia. Consistent patterns in soil moisture attributes were observed among rehabilitated sites with generally marked differences from remnant sites. Remnant site soil profiles had generally higher Θ after drying than rehabilitated sites and maintained high Ψ for extended periods after rain events. There was a relatively rapid decline of Ψ on reconstructed soil profiles compared with remnant sites although the times of decline onset varied. This response indicated that vegetation restoration sites released soil moisture more rapidly than remnant sites but the rate of drying decreased with increasing rehabilitation age and increased with increasing tree stem density. The rapid drying of mine rehabilitated sites may threaten the survival of some remnant forest species, limit tree growth, and delay restoration of self‐sustaining native ecosystem.

Synthesis, characterization and water retention study of biodegradable Gum ghatti-poly(acrylic acid–aniline) hydrogels

A natural polysaccharide, Gum ghatti (Gg), was modified to prepare cross-linked hydrogels using the grafting method initiated by gamma-radiation. Acrylic acid (AA) and aniline monomers were used as the grafted monomers. Grafted copolymer based on Gg and AA was synthesized using N, N′-methylene-bis-acrylamide as a cross linker. The effects of monomer and cross linker concentration, gamma dose and the amount of solvent on the grafting percentage and percentage swelling were investigated. The degree of grafting and percentage swelling were found to be greatly dependent on the reaction parameters. Whereas, aniline monomer was absorbed into the network of Gg-cl-poly(AA), followed by a polymerization reaction between aniline monomer initiated by gamma-radiation. Biodegradation of synthesized hydrogels was also investigated using a composting soil method and Gg-cl-poly(AA-ipn-aniline) showed better degradation efficiency in comparison to Gg-cl-poly(AA). Furthermore, the degraded sample was characterized by FT-IR and surface morphology by SEM. Our results showed that Gg-cl-poly(AA) degraded at a rate of ∼6.1% after 6 days, whereas the degradation rate for Gg-cl-poly(AA-IPN-aniline) was ∼10%. Application of hydrogels to improve the water retention properties of different soils was studied for agricultural purposes and found that the IPN hydrogel can improve the moisture retention capacity of soil for cultivation.