Acidic Sandy Loam Soil Research Articles

Field trials of micropropagated clones of triploid white and grey poplars

In this article we present, for the first time, the results of 20 years field trials of triploid white poplar (Populus alba L.) and grey poplar (Populus x canescens Sm.) clones propagated by in vitro culture in different edaphic conditions (6 clones in total). The soils of the test plots differ in fertility, chemical and physical-chemical characteristics, which had a significant impact on the plants’ capacity for survival, health and growth. Low fertile, dry, acidic sandy loam and sandy soils are the least suitable for cultivating of in vitro micropropagated clones. In this case we had sandy loam soils on glaciofluvial monomineral quartz sands. The response to adverse growing conditions largely depended on the genotypic characteristics of the plants. The grey poplar clone named Hopersky 1 cultivar has shown the highest ecological plasticity as it has broad genetic basis (it is a hybridogenic species and allotriploid).

Retention and transport of mecoprop on acid sandy-loam soils

Interaction with soil components is one of the key processes governing the fate of agrochemicals in the environment. In this work, we studied the adsorption / desorption and transport of mecoprop (methylchlorophenoxypropionic acid or MCPP) in four acid sandy-loam soils with different organic matter contents. Kinetics of adsorption and adsorption/desorption at equilibrium were studied in batch experiments, whereas transport was studied in laboratory columns. Adsorption and desorption were found to be linear or nearly-linear. The kinetics of mecoprop adsorption were relatively fast in all cases (less than 24h). Adsorption and desorption were adequately described by the linear and Freundlich models, with KF values that ranged from 0.7 to 8.8Ln µmol1−nkg−1 and KD values from 0.3 to 3.6Lkg−1. The results of the transport experiments showed that the retention of mecoprop by soil was very low (less than 6.2%). The retention of mecoprop by the soils in all experiments increased with organic matter content. Overall, it was observed that mecoprop was weakly adsorbed by the soils, what would result in a high risk of leaching of this compound in the environment.

FIELD EVALUATION OF SOIL AND WHEAT RESPONSES TO COMBINED APPLICATION OF HARDWOOD BIOCHAR AND INORGANIC FERTILIZERS IN ACIDIC SANDY LOAM SOIL

SUMMARYBiochar application appears to be a promising method to improve soil physicochemical and biological properties by increasing soil carbon. Along with the influence of hardwood biochar on wheat growth, yield and soil quality for a period of two years, this study also evaluates the major soil parameters to be taken as minimum data set while assessing the impact of hardwood biochar in an acidic sandy loam soil. Five fertilizer treatments combining inorganic fertilizers and biochar were applied: unfertilized control (T1); 100% NPK (T2); 5 Mg ha−1 biochar (T3); 100% NPK + 5 Mg ha−1 biochar (T4); and 50% N + 100% PK + 5 Mg ha−1 biochar (T5). Biochar application (T3 vs. T1; T4 and T5 vs. T2) significantly increased leaf chlorophyll content, net photosynthesis rate, leaf N concentration and above and below-ground biomass, with improved wheat yield and grain quality (total grain protein and carbohydrate). Soil pH, water-holding capacity, available nutrients (N, P and K), organic carbon and its fractions also enhanced in biochar applied plots with reduced bulk density. Increased activities of soil enzymes urease, phosphatase, dehydrogenase, fluorescein di-acetate and arylsulphatase were recorded in biochar treatment along with significant increase in N recovery index (22%) and agronomic efficiency (40%). Multivariate analysis identified activity of phosphatase, pH and humic acid to fulvic acid ratio as the indicators to explain the total variance from biochar addition in acidic sandy loam soil under wheat cultivation. Soil quality index showed a significant improvement when biochar was added with reduced N doses (T5). This study confirms the efficacy of biochar as a soil conditioner when applied with reduced N fertilizer and would be a sustainable option to improve wheat production and soil quality in acidic sandy loam soils of northeast India.

Analyzing the impacts of three types of biochar on soil carbon fractions and physiochemical properties in a corn-soybean rotation

Biochar is a solid material obtained when biomass is thermochemically converted in an oxygen-limited environment. In most previous studies, the impacts of biochar on soil properties and organic carbon (C) were investigated under controlled conditions, mainly laboratory incubation or greenhouse studies. This 2-year field study was conducted to evaluate the influence of biochar on selected soil physical and chemical properties and carbon and nitrogen fractions for two selected soil types (clay loam and a sandy loam soil) under a corn (Zea mays L.)-soybean (Glycine max L.) rotation. The three plant based biochar materials used for this study were corn stover (CS), ponderosa pine (Pinus ponderosa Lawson and C. Lawson) wood residue (PW), and switchgrass (Panicum virgatum L.) (SG). Data showed that CS and SG significantly increased the pH of acidic soil at the eroded landscape position but produced no significant change in soil pH at the depositional landscape position. The effects of biochar treatments on cold water extractable C (WSC) and nitrogen (WSN) fractions for the 0–7.5 cm depth were depended on biochar and soil type. Results suggested that alkaline biochars applied at 10 Mg ha−1 can increase the pH and WSC fraction of acidic sandy loam soil, but the 10 Mg ha−1 rate might be low to substantially improve physical properties and hot water extractable C and N fractions of soil. Application of higher rates of biochar and long-term monitoring is needed to quantify the benefits of biochar under field conditions on soils in different environmental conditions.

Organic amendments: Effect on carbon mineralization and crop productivity in acidic soil

Addition of organic amendment with inorganic fertilizers is a suitable strategy to achieve sustainable agricultural production. But this practice is associated with increased carbon mineralization leading to release of carbon dioxide, a potential greenhouse gas for global warming. In this perspective, the present experiment was conducted in acidic sandy loam soils of north-east India to characterize the carbon mineralization, soil enzyme activities and okra (Abelmoschus esculentus L.) productivity under three (farmyard manure, vermicompost and biochar) commonly used organic amendments when added with inorganic fertilizers. Eight treatments were laid in a randomized block design with three replications. Vermicompost application increased the activities of soil enzymes with greater availability of soil nitrogen, phosphorous and potassium while biochar (hardwood) addition decreased the enzyme activities. Addition of biochar recorded the lowest rate of carbon mineralization (9%), the highest half -life of carbon (64%), higher soil organic carbon (12%) and stable organic carbon fractions (F3 fraction-12% and F4 fraction- 9%) with the highest okra yield compared to vermicompost and farmyard manure. Plant morphological attributes (plant height, leaf number, leaf area and photosynthesis of okra) were significantly enhanced due to addition of organics especially vermicompost and biochar with inorganic fertilizers. The addition of biochar recorded lower benefit cost ratio (3.5 and 3.8) but its application with inorganic fertilizers recorded the highest agronomic efficiency signifying potentiality to uphold efficient nitrogen use and environmental sustainability. Thus, addition of biochar in acidic soil would be a sustainable option to reduce carbon mineralization and uphold crop productivity.

Cadmium phytoextraction from loam soil in tropical southern China by Sorghum bicolor

ABSTRACTThe cadmium (Cd) uptake characteristics by Sorghum bicolor cv. Nengsi 2# and Cowley from the acidic sandy loam soil (pH = 6.1) during the entire growth period (100 days) were investigated in pot outdoors in a tropical district of southern China, Hainan Island. The Cd-spiked levels in soil were set as 3 and 15 mg/kg. Correspondingly, the available Cd levels in soil extracted by Mehlich III solution were 2.71 and 9.41 mg/kg, respectively. Basically, two varieties in a full growth period (100 days) did not show a significant difference in their growth and Cd uptake. Under high Cd stress, the plant growth was inhibited and its biomass weight and height decreased by 38.7–51.5% and 27.6–28.5%, respectively. However, S. bicolor showed higher bioaccumulation capability of Cd from soil to plant [bioconcentration factor (BCF)>4], and higher transfer capability of Cd from roots to shoots [translocation factor (TF)>1] under high Cd stress; Cd contents in the roots, stems, and leaves of S. bicolor reached 43.79–46.07, 63.28–70.60, and 63.10–66.06 mg/kg, respectively. S. bicolor exhibited the potential phytoextraction capability for low or moderate Cd-contamination in acidic sandy loam soil.

Responses of Soil Enzymes and Carbon Mineralization to Applied Organic Amendments: A Short-term Study in Acidic Sandy Loam Soil

Predicting carbon (C) mineralization due to fertilizer application is important for predicting carbon dioxide (CO2) emissions into the atmosphere. This study was conducted to evaluate the effects of different organic amendments and inorganic fertilizers on C mineralization and soil enzyme activities along with the changes in soil pH, available nitrogen (N) and phosphorus (P). Eight treatments were applied using inorganic fertilizer and organic amendments (FYM, vermicompost and biochar) at different rates. Higher activities of soil enzymes (urease, phosphatase and dehydrogenase) were recorded till 60 days of incubation with addition of organic amendments. Among the applied organic amendments, vermicompost showed greater availability of N and P. Both vermicompost and FYM application recorded enhanced activities of soil enzymes and C mineralization rate while biochar application noted higher C half-life and soil pH. Thus, addition of biochar in acid soil would be a sustainable option to reduce the C mineralization which also maintains nutrient status of sandy loam soil of north-east India.

The study of the fertilizing effect of wheat straw ash in a greenhouse experiment

The effect of wheat straw ash as a fertlizizer was studied in a pot experiment with an acidic sandy loam soil (pHKCl=4.9) with weak K and P supply. The test plant was ryegrass (Lolium perenne). The treatments were the following: 1. control untreated soil, 2. NPK fertilizer, 3. small dose of ash (1.4 g kg-1), 4 large dose of ash (2.8 g kg-1), 5. small dose ash completed with NP fertilizers. Soil parameters (pHH2O, pHKCl, ammoinum-lactate soluble P, K, 0.01 M CaCl2 soluble PO43--P, K, Mn, Cu, Zn ) and plant parameters (yield, P, K, Ca, Mg, Zn, Mn uptake) were investigated. Based on the analysis of the straw ash sample and the results of pot experiment it can be stated that the wheat straw ash is suitable for the fertilization of the studied soil. The small dose ash completed with NP resulted in the largest yield increment (43%). In order of the treatments the pHKCl changes to: 4.9, 4.8, 5.2, 5.8, 5.1. As the N : P2O5 : K2O ratio is 0 : 1: 3.5 in the wheat straw ash sample, to reach optimal yield ash should be completed with N and P.

Response of maize to coconut husk ash application in an acid sandy-loam soil in Abakaliki, South-East Nigeria

Response of maize to coconut husk ash application was evaluated in an acid sandy loam soil under Abakaliki agroecology in South-East Nigeria. A land area measuring 0.03 ha was used for the experiment. The field was laid out using Randomized Complete Block Design with five treatments of coconut husk ash at 0, 2, 4, 6 and 8 t ha 1, replicated four times. Oba Super II hybrid maize was used as the test crop. Results showed that soil texture remained sandy loam after cropping. Hydraulic conductivity of coconut husk ash amended soil except the one applied at 2 t ha−1 was significantly (P coconut husk ash at 8tha−1> coconut husk ash at 4t ha−1 >coconut husk ash at 2 t ha−1 > control. It was concluded tha amendment of soil with coconut husk ash could be recommended for reducing soil acidity and higher maize production in an acid sandy loam.

Application of csm- ceres-maize model for seasonal and multi-decadal predictions of maize yield in under subtropical condition of Chitwan, Nepal

The average maize yield of 2.5 t/ha in sub-tropical terai and inner terai of Nepal has been very less than its potential yield of about 5.0 t/ha, for which changing climatic scenarios have been reported the critical factors. Cropping system Model (CSM)-Crop Estimation through Resource and Environment Synthesis (CERES)-Maize, embedded under Decision Support System for Agro-technology Transfer (DSSAT) ver. 4.2 was evaluated from a datasets of field experimentation by growing four diverse maize genotypes viz. full season OPV (Rampur Composite), Quality Protein Maize (Posilo Makai-1), Hybrid (Gaurav) and Pop corn (Pool-12) under three different planting dates (September 1, October 1 and November 1) in 2009-10 at Rampur Campus, Chitwan. The experiment was laid out in two factor factorial randomized complete block design (RCBD) with three replications in slightly acidic (pH 6.7) sandy loam soil having low soil available N( 0.49%) and K (148 kg/ha) and medium P (16.3 kg/ha) status. The ancillary and yield data obtaining from field experiment was analyzed from the M-Stat C software and recorded that Gaurav hybrid produced significantly higher yield under September 1 planting (5.86 t/ha) followed by Posilo Makai 1 (5.55 t/ha), Rampur Composite (5.1t/ha) and the least with Pool-12 (3.45 t/ha). Further, the heat use efficiency of diverse maize genotypes were also calculated by using the mean temperature based accumulative heat unit system and found the stable yields only with Rampur Composite for all planting dates and the rest genotypes were suitable only to the early winter plantings. Model calibration was done by using September 1 planting date for all 4 maize genotypes while validation was accomplished by using the remaining treatments for predicting growth and yield of different maize genotypes. The year 2006- 07 was found 13, 18, 23 and 7% higher in producing the maize yield than the standard year 2009-10 for Rampur Composite, Posilo Makai-1, Gaurav and Pool-12, respectively. Further, the different climate change scenarios as advocated by IPCC (2007) for 2020, 2050 and 2080 from base line of 2009-10 was studied to simulate the growth and yield performance of diverse maize genotypes with September 1 planting date and found that there would be increment in winter maize yield up to 2020 scenario of climate change and the drastic yield loss would be on 2050 to 2080 scenarios under the present levels of agronomic management options and urged for the new climate change adaptation and mitigation production technologies.Journal of Maize Research and Development (2015) 1(1):86-97DOI: http://dx.doi.org/10.5281/zenodo.34283

Long-term influences on nitrogen dynamics and pH in an acidic sandy soil after single and multi-year applications of alkaline treated biosolids

We present results of a four year field study examining the changes in seasonal soil mineral nitrogen (SMN) and soil pH from the application of an alkaline treated biosolid (ATB) in an acidic sandy loam soil. Results of two management practices, annual ATB applications and a single application, and different rates of ATB (0, 7, 14, 28 and 42Mgha−1) were also compared over the four year study period. Corn (Zea mays L.) was used as the test crop throughout the study. Soil pH was effectively modified in all treatments receiving ATB rates, compared to the control, under both management practices but best results were achieved under annual ATB application. Soil cation exchange capacity was increased under annual ATB applications, by 3× at the highest ATB. Compared to the control, soil nitrogen and pH displayed significant changes under frequent additions with increasing rates of ATB. Our results indicate that a single application at the highest ATB rate had a residual effect on soil pH but little impact on subsequent SMN dynamics. Average soil mineral nitrogen (SMN) concentrations in the single application management ranged from 8.3 to 9.3mgkg−1 in the final three years of the study but ranged from 8.5 to 12.1mgkg−1 under the annual application management. In contrast, annual applications of ATB at rates ≥14Mgha−1 increased seasonal SMN by 15–42% and soil pH by 1–1.5 pH units. Seasonal SMN dynamics under different ATB rates and management practices were also examined using a soil nitrogen ratio (SNR) and as an area under the seasonal SMN curve.

Land degradation impact on soil organic carbon and nitrogen stocks of sub-tropical humid grasslands in South Africa

Land degradation is recognized as a main environmental problem that adversely depletes soil organic carbon (SOC) and nitrogen (SON) stocks, which in turn directly affects soils, their fertility, productivity and overall quality. While it is expanding worldwide at rapid pace, quantitative information on the impact of land degradation on the depletion of SOC and SON stocks remains largely unavailable, limiting the ability to predict the impacts of land management on the C losses to the atmosphere and associated global warming. The main objective of this study was to evaluate the consequences of a decrease in grass aerial cover on SOC and SON stocks. A degraded grassland showing an aerial cover gradient from 100% (Cov100, corresponding to a non-degraded grassland) to 50–75% (Cov75), 25–50% (Cov50) and 0–5% (Cov5, corresponding to a heavily degraded grassland), was selected in South Africa. Soil samples were collected in the 0.05m soil layer at 48 locations along the aerial cover gradient and were subsequently separated into the clay+silt (2–20μm) and sand (20–2000μm) fractions, prior to total C and N analysis (n=288). The decline in grass aerial cover from 100% to 0–5% had a significant (P<0.05) impact on SOC and SON stocks, with losses by as much as 1.25kgm−2 for SOC and 0.074kgm−2 for SON, which corresponded to depletion rates of 89 and 76%, respectively. Furthermore, both the C:N ratio and the proportion of SOC and SON in the silt+clay fraction declined with grass aerial cover, which was indicative of a preferential loss of not easily decomposable organic matter. The staggering decline in SOC and SON stocks raises concerns about the ability of these acidic sandy loam soils to sustain their main ecosystem functions. The associated decrease in chemical elements (e.g., Ca by a maximum of 67%; Mn, 77%; Cu, 66%; and Zn, 82%) was finally used to discuss the mechanisms at stake in land degradation and the associated stock depletion of SOC and SON stocks, a prerequisite to land rehabilitation and stock replenishment.

Influence of organic wastes amendment on growth and foliar yield of jute mallow &lt;i&gt;Corchorus olitorius&lt;/i&gt; (linn.) In South Western Nigeria

This study investigated the growth and foliar yield responses of jute mallow (Corchorus olitorius Linn.) on soils amended with ashed and unashed corn cob and coconut husk agro-waste. Slightly acidic (pH=6.20) sandy loam soil were collected and incubated for six and twelve weeks respectively for the study, with agro-wastes [coconut husk ash (CHA), coconut husk unashed (CHU), corn cob ash (CCA) and corn cob unashed (CCU)] under greenhouse conditions. A completely randomized design was adopted with three replicates. The results showed that the corn cob ash and coconut husk ash positively enhanced soil chemical properties than their unashed version. At 2 WAP, the mean plant height ranged from 2.70 ± 0.12 cm to 3.88 ± 0.12 cm; the mean total leaf count from 3.60 ± 0.05 to 4.0 ± 0.05 and mean leaf area from 0.54 ± 0.21 cm2 to 2.48 ± 0.21 cm2 and at 8 WAP, the mean stem girth ranged from 0.43 ± 0.07 cm to 1.02 ± 0.07 cm for C. olitorius planted in soils incubated for six weeks with agro-wastes. This trend increased with the age of C. olitorius and with increase in agro-waste applications in the order CCA&gt;CHA&gt;CHU&gt;CCU. These growth parameters, except the plant height were of higher values in 6 weeks soil incubation than 12 weeks soil incubation. The highest mean yield (17.93g/pot) of C. olitorius was obtained in soil pots amended for 12 weeks with 5 t/ha of CHU. The increase growth and foliage yield obtained in this study showed that soils amended with ashed and unashed corn cob and coconut husk waste have the potential of promoting the production of vegetables, especially C. olitorius and also ensuring environmental sustainability.Key Words: Agro-waste, Amended soil, Coconut hust, Corn cob, Corchorus olitorius, Greenhouse, Vegetable

Distribution, status, and conservation of Camellia changii Ye (Theaceae), a Critically Endangered plant endemic to southern China

AbstractThe distribution of the endemic threatened plant Camellia changii Ye (Family Theaceae) is restricted to a small area in southern China, and little else is known about its status in the wild. To provide information for the conservation of C. changii we investigated its distribution, population size and structure, and habitat, and assessed its conservation status. Surveys confirmed that the species grows in a narrow band along both sides of a 4 km long segment of a stream in Ehuangzhang Nature Reserve, under the discontinuous canopy of a secondary evergreen broadleaved forest on well-drained, acidic sandy loam soil. We found a total of 1,039 individuals of C. changii. The population has a high flowering rate but a low seed-setting rate. The population appears to be in decline because no seedlings and few young plants were evident. Our findings indicate that C. changii should be categorized as Critically Endangered on the IUCN Red List. We have recommended an integrated species-conservation plan for the species that includes patrolling the Ehuangzhang Nature Reserve to prevent plant removal, establishing an ex situ living collection that contains the entire wild genetic diversity (accomplished by grafting of short cuttings from all wild individuals), facilitating propagation for commercial use, and implementing reintroduction to augment the wild population.

Optimum N Rate for Sustainable Rice-Wheat System Under Tillage and Crop Residue Management

Application of an optimum rate of nitrogen is very crucial to maintain the sustainability of a rice-wheat cropping system (RWS). A three-year field experiment was conducted on acid sandy loam soil to select the best N-management practice, along with tillage and crop residue (CR) incorporation for RWS. Changes in soil properties were assessed to determine the effect of tillage and crop residue application on soil fertility, loss and uptake of N, and yield of rice and wheat (RW) crops. Application of CR and intensive tillage increased the N leaching loss; however, it also increased N uptake and yield of RW crops and resulted in minimal degradation of soil environment. Overall results of loss, uptake, N-use efficiency, and yield attributes of RW crops indicated that a comparatively lower rate of N along with RW residue incorporation in combination with less intensive puddling for rice and medium-intensive tillage for wheat can be opted as sustainable management practices. Thus, the use of comparatively lower rate of N will reduce water pollution from extra leached N and reduce the cost of farming, too. On the other hand, use of RW residue will enrich the soil organic carbon pool and improve the quality of the soil. Use of less intensive tillage along with RW residue application will increase the porosity of the soil, reduce soil erosion, and help sustain the RW system.

Impact of potassium fertilizers with different active ingredients and dosages on potato yield in experiments in the Nyírség region

A five-year experiment was carried out in the Nyírség on its characteristic soil type, brown forest soil to investigate the impact of three types of potassium fertilizers (potassium chloride, potassium sulfate and Patentkali) in three different dosages (80, 160, 240 kg/ha K20), under non-irrigated conditions applying the same dosages of N, P in all treatments (the applied amount was different between years) in 10 treatments including the control on 50 m2-parcels with 3 or 4 replicates. The test plant was cultivar Desiree, Kondor, Agria and Pannonia in 1998 and 2000, 2001, 2002 and 2003, respectively. The obtained yields were analyzed by an analysis of variance. Based on the five-year results, the highest yields on the acidic sandy and sandy loam soils were obtained in the treatments with 530-800 kg/ha Patentkali containing 30% of K and 10% of magnesium active ingredients in addition to the same amounts of N and P applications. The dosage of 530 kg/ha Patentkali contains 160 kg/ha K+ 53 kg/ha Mg active ingredients, while the dosage of 800 kg/ha Patentkali contains 240 kg/ha K+ 80 kg/ha Mg active ingredients. It can be concluded that the potassium chloride fertilizer (KCI) was the least effective as regards yields and Patentkali proved to be the most effective fertilizer, it had higher yields than even those of potassium sulfate, the difference in the 160 kg/ha treatments was 17.7%, which was a significant difference. Based on the results of the multi-year experiment, we recommend to apply 530 kg/ha Patentkali fertilizer (160 kg/ha K+ 53 kg/ha Mg active ingredients) for the fertilization in potato under non-irrigated conditions on the acidic sandy and sandy loam forest soils of the Nyírség, which proved to be the most effective treatment and with which we could obtain 30 t/ha yield in the average of the years (with the simultaneous application of N and P).

Applications of reduced tillage in hills of central Nepal

Conventional tillage practices on steep and fragile landscape of Himalayan hills result in significant loss of topsoil during rainy season. Soil erosion in Nepal mid-hills is the most critical during pre-monsoon season. Many reviews argue that reduced tillage could be an option to tackle this problem. However, very few field experiments to evaluate reduced tillage systems have to date been conducted in this region. Thus, a field experiment was initiated in factorial randomized complete block design on acidic sandy loam soil (Lithic Dystochrept) during the summer season of 2001 at Kathmandu University (1500 masl) to assess the effects of tillage and cropping patterns on soil and nutrient losses, crop yield and soil fertility. Two main treatments viz. conventional and reduced till, and two sub-treatments viz. sole maize ( Zea mays) and maize + soybean ( Glycine max) were considered. Soil organic carbon (OC), total nitrogen (N), plant available phosphorus (P) and exchangeable potassium (K) were determined for the original soil and eroded sediment using standard methods. Two years of data indicated annual soil and nutrient losses to be significantly lowered by reduced till as compared to conventional till. Total annual soil loss from conventional and reduced till was 16.6 and 11.1 Mg/ha, respectively. Similarly, annual nutrient losses associated with the eroded sediment were 188 kg OC/ha, 18.8 kg N/ha, <1 kg P/ha and 3.8 kg K/ha for conventional till and 126 kg OC/ha, 11.8 kg N/ha, <1 kg P/ha and 2.4 kg K/ha for reduced till. Soil OC and N losses were significantly higher in conventional till and this may be one of the major causes of fertility depletion in the Nepalese hills. Soil chemical properties did not differ due to tillage and cropping systems; however, over years pH, N and P were increased irrespective of treatments. Although treatments were at par for maize grain yield, conventional till + soybean produced highest grain yield (4.0 Mg/ha) followed by reduced till + soybean (3.9 Mg/ha) and conventional till sole maize (3.8 Mg/ha). Mixed cropping of legumes and maize do not help conserve soil and nutrient loss in hills of central Nepal. Thus, reduced till could be a viable option for minimizing soil and nutrient losses without sacrificing economic yields in central hills of Nepal.

Response of the microbial community to copper oxychloride in acidic sandy loam soil

Determining the response of different microbial parameters to copper oxychloride in acidic sandy loam soil samples using cultivation-dependent and direct microscopic techniques. Culturable microbial populations were monitored for 245 days in a series of soil microcosms spiked with different copper oxychloride concentrations. Microbial populations responded differently to additional Cu. Protistan numbers and soil metabolic potential decreased. Experiments with more soil samples revealed that metabolic potential was not significantly affected by < or =100 mg kg(-1) additional Cu. However, a negative impact on protista was noted in soil containing only 15 mg kg(-1) EDTA-extractable Cu. The negative impact on protistan numbers was less severe in soils with a higher phosphorous and zinc content. Bacterial populations responded differently, and protista were most sensitive to elevated Cu levels. Protistan numbers in soil from uncultivated land were higher and seemed to be more sensitive to additional Cu than the numbers of these organisms in soil originating from cultivated land. Protistan sensitivity to small increases in Cu levels demonstrates the vulnerability of the soil ecosystem to Cu perturbations, especially when the importance of protista as link in the flow of energy between trophic levels is considered.

Effect of nitrogen and phosphorus fertilization on growth, yield and nutrient uptake of winter rice bean (Vigna umbellata)

A field experiment was conducted during the winter (rabr) season of 1994-95 and 1995-96 at Bhubaneshwar, in acidic sandy-loam soil, to study the effect of nitrogen and phosphorus fertilization on growth, yield and nutrient uptake of rice bean [Vigna umbellata (Thumb.) Ohwi &amp; Ohashi]. Application of nitrogen at 40 kg/ ha and phosphorus at 60 kglha markedly influenced the branches and pods/ plant, seedslpod and 1,000-seed weight and significantly increased the seed . yield by 57.3 and 27.7% over the respective control. The N and P content as well as their uptake in seed and haulm also increased significantly up to 40 kg N and 60 kg P,O$ha.

Response of late-sown wheat (Aticum aestivum) to irrigation schedules

A field experiment was conducted during the winter seasons of 1995-97 on acidic sandy-loam soil at Ranchi, to find out the critical growth stages for irrigations as per availability of water for higher and profitable production of late- sown wheat (Triticum aestivum L. emend. Fiori &amp; Paol.). Wheat receiving 4 irrigations at crown-root-initiation, maximum tillering, boot and milk stages gave maximum grain (2,707 kg/ha) and straw (4,164 kglha) yields, with net return of Rs 1 1,855lha and net benefit of Rs 1.31 on each rupee investment. This treatment showed significant edge over all other irrigation schedules except the crop receiving 3 irrigations at maximum tillering, boot and milk stages (2,523 kg/ha grain yield, and Rs 10,474lha net return with 1.23 benefit : cost ratio). Among 2 irrigation schedules, wheat irrigated at maximum tillering and milk stages gave the maximum grain (2,011 kglha) and straw (2,823 kglha) yields, with net return of Rs 7,328tha and net benefit of Rs 0.92lrupee investment.