Maintenance Of Soil Organic Matter Research Articles

Rejuvenation of Coastal Sandy Soils through Organics

The coastal zone represents the transition from terrestrial to marine influences and vice versa. They are predominated by sandy soil texture, and have low agricultural productivity due to their properties and are vulnerable to erosion. Effective maintenance of soil organic matter is found to be a pre-requisite to ensure soil health and crop productivity. Therefore, organics based rejuvenation methods for coastal sandy soils need to be developed. A pot culture experiment was done at Kochuveli, Industrial area, in the coastal belt of Thiruvananthapuram district, Kerala, with Amaranthus (variety: Arun) as test crop. The experiment was conducted in a completely randomized design (CRD) with 12 treatments and 3 replications. In the study, effect of different organic manures such as FYM, coirpith compost, vermicompost, city compost, biochar and thermochemical organic fertilizer (TOF), with and without lime on plant growth and yield, soil organic carbon and nutrient dynamics in the southern coastal sandy soils were studied. Soil management using organic manures had considerable impact on the growth and yield characteristics of the crop. Also the analyses of post-harvest soil for nutrient parameters showed that the highest value for organic carbon, nitrogen and potassium were recorded in soil treated with lime+TOF, while the highest value for available phosphorous was recorded in treatment lime+vermicompost. The study showed that soil test based lime application and basal application of TOF @ 25 t ha-1, top dressing with fresh cow dung slurry @ 1kg per 10 litres, along with 272.7 kg rock phosphate and 122.5 kg potassium sulphate ha-1 was the best treatment to improve the soil quality, growth and yield of amaranthus in coastal sandy soils in Thiruvananthapuram district.

Variation in Phenology of Banj Oak (Quercus Leucotrichophora) Tree Across Different Elevations in the Kumaun Himalayas, India.

Changes in phenological events have been caused by the present phenomenon of climate change. The elevation is another important factor which leads to the variations in phenological events. The Banj Oak plays holds a vital position as a keystone species in the moist temperate forests of the Central Himalayas, and contribute to human well-being by providing essential benefits such as biodiversity conservation, maintenance of soil organic matter, and the ability to retain water. Thus, this study aims to evaluate the various phenological events of Q. leucotrichophora tree species along the elevation gradients. The elevation gradients are low (1400-1600 m), mid (1700-1900 m) and high (2000-2200 m). At each elevation, three sites were selected for the detailed phenological study. The observations were made from bud initiation to seed fall. In general, leaf bud break and leaf fall were initiated earlier in low-elevation species. In comparison with the middle and high elevation, at low elevation the growth initiation occurred in February and March when the temperature had begun. Comparisons with previous studies have shown that some phenological events began to occur early. The study clearly indicates that climatic irregularities have influenced or altered the phenological events of species. It can be said that the phenological events changes with climatic factors, which are responsible for earlier or delayed phenophases. Understanding phenology and its variations can offer significant data. Consequently, this knowledge can be highly valuable for agricultural practices, which necessitate advanced information on particular stages of tree growth.

THE INFLUENCE OF BIOLOGICAL PREPARATIONS AND THEIR MIXTURES ON SOIL AGROCHEMICAL PROPERTIES IN WINTER WHEAT

Intensive tillage accelerates soil erosion, reduces the content of organic matter and carbon in the soil. Scientists around the world talk extensively about soil conservation policies. The process of accumulation and maintenance of soil organic matter is important for the long-term preservation of agro-system productivity. Crop production technologies applied should increase carbon sequestration in the soil (Kaiser, Kalbitz, 2012; Baumhardt et al., 2015). The study was conducted in 2018–2019 in the winter wheat crop “Sailor”. An experiment with two factors was performed: preparations of biological origin and their mixtures were used with the application of different tillage technologies. The aim of this study is to determine the effect of biological preparations on soil agrochemical properties in winter wheat crop using different tillage technologies. The use of biological preparations and their mixtures, in many cases, increased the content of water-soluble (labile) carbon in the soil comparing compensatory nitrogen 8 kg t of straw, without biological preparations to stimulate straw mineralization . The content of labile carbon was particularly increased by mixtures of two preparations (Ruinex + Penergetic k, Ruinex + Azofix and Penergetic k + Azofix) using both tillage technologies: when applying no-tillage, the content of soluble carbon increased from 2.9% to 12.2%, and when using the mixtures in ploughless tillage – from 1.4% to 10.3. The combination of the three preparations increased the content of soluble carbon by 5.4% more in ploughless technology, in no-tillage – only 0.5%. The use of one-component biological preparations in ploughless tillage also increased the content of water-soluble carbon, and in no-tillage – reduced it but insignificantly.

The Distribution of Soil Micro-Nutrients and the Effects on Herbage Micro-Nutrient Uptake and Yield in Three Different Pasture Systems

Pasture micro-nutrient concentrations are often deficient for herbage productivity and the health of livestock. The aim of this study was to investigate soil and herbage micro-nutrient content and the effects on yield on the three pasture systems of the North Wyke Farm Platform (NWFP): high-sugar grass + legume mix minus nitrogen (N) fertilizer (blue/HSG + L); permanent pasture plus N fertilizer (green/P + N); high-sugar grass plus N fertilizer (red/HSG + N). The locations with high soil total micro-nutrient concentrations had a greater slope and higher soil organic matter (SOM) content. Herbage micro-nutrient concentrations were often greater at the locations with high soil total micro-nutrient concentrations. The concentration and uptake of nearly all micro-nutrients was greatest in the herbage of the green/P + N system, which had the highest SOM content, whereas they were often lowest in the red/HSG + N system, which had the lowest SOM and the highest yield, indicating biomass dilution of micro-nutrients in the herbage. At the locations with high soil micro-nutrient concentrations, yield was higher than at locations with low micro-nutrient concentrations, and was equal across the three pasture systems, regardless of fertilizer N treatment. Variation in micro-nutrient uptake/yield in the blue grass–legume system was predominantly explained by the soil molybdenum (Mo) concentration, possibly relating to the requirement for Mo in biological nitrogen fixation. There was, therefore, a trade-off in ploughing and re-seeding for higher yield, with the maintenance of SOM being important for herbage micro-nutrient content.

Soil Quality Assessment of the Lower Niger River Plain Alluvial Soils in Bayelsa State, Nigeria, for Sustained Productivity

Floodplain soils worldwide are very useful for agricultural production and food security. But, the floodplains of Bayelsa State are under-utilized due to lack of technical information and knowledge on the nutrient status and other soil characteristics. This study therefore, assessed the soil quality of lower Niger River floodplain soils in Bayelsa State, Nigeria for sustained productivity and food security. Alluvial soils from different river plains in Bayelsa State, Southern Nigeria were characterized and fertility assessed. Pedogenic soil samples from the levee crest, middle slope, lower slope and recent alluvial soils from the channels of present active rivers were collected from identified genetic horizons of soil profiles and analyzed for physical and chemical properties using standard methods and the soils fertility status evaluated using Soil Fertility Index (SFI) and Soil Evaluation Factor (SEF). The soils were dominantly silt loam followed by silty clay loam and loam except Elemebiri 3 (ELM3) and Trofani 3 (TFN3), dominated by loamy sand and sandy loam. pH (5.31-7.00) was moderately acid to neutral and organic matter content, generally low to moderate, ranging from 0.19-3.88%. Total N values was also low while available P was low to moderate. The exchange complex was dominated by Ca²⁺ and ECEC values were low. The SFI values were higher than the SEF values in al the Soil Mapping Units (SMUs), contributed by pH, organic matter and phosphorus. Both SFI and SEF values decreased with increase in depth for all the soil mapping units except Trofani 1 (TFN1) where the bottom layers recorded higher SFI values and Elemebiri 3 (ELM3) for SEF. Though the soils nutrient concentration was generally low to moderate, both SFI and SEF evaluated the soils as fertile contributed mainly by organic matter, available P and pH. Since biomass accumulation contributed greatly to improvement of soil fertility and physical structure, soil organic matter maintenance should be given top priority in these soils for sustained productivity and food security.

Management Drives Differences in Nutrient Dynamics in Conventional and Organic Four-Year Crop Rotation Systems

Application of exogenous N fertilizers provides agronomic benefits but carries environmental liabilities. Managing benefits and liabilities of N-based fertilizers in conventional (CNV) and organic (ORG) cropping systems might be improved with better knowledge of nutrient dynamics, the generation of intrinsic N, and maintenance of soil organic matter. This study evaluated mineral N dynamics, yields, residue inputs, and change in soil organic C (SOC) and total N (TN) in strip-tilled, four-year crop rotations [corn (Zea mays L.)-soybean (Glycine max [L.] Merr.)-wheat under-seeded with alfalfa (Triticum aestivum L./Medicago sativa L.)-alfalfa] over eight years of production under CNV management using mineral-N (NO3NH4) and chemical pesticides or ORG management using organic-N (animal manure) and no chemical treatments. In ORG, N availability increased over time, but did not benefit ORG yields due to poor control of insects and weeds. Corn, soybean, and wheat grain yields were 1.9 to 2.7 times greater in CNV. In general, SOC was lost in CNV but did not change in ORG. Cumulative yield N removals exceeded cumulative fertilizer-N inputs by an average of 78% in CNV and 64% in ORG. These results indicated ORG management supported N availability by generating intrinsic N.

Effect of land use patterns on size distributions and aggregates stability in the mountainous areas of north-western Himalayas, India

A study was conducted to assess the impact of different land uses and management on soil aggregate stability in sub-mountainous area of Jammu state, India. Soil samples were collected from five different land uses systems viz., forest, horticulture, agriculture, pasture and degraded lands from each of the five locations for surface (0-15cm) and sub-surface (15-30cm) of soil depth. Soil aggregate stability was determined by dry and wet sieving methods. Dry sieving was determined without immersion in water and wet sieving was immersion in water, respectively. Soil properties such as soil organic carbon (SOC), bulk density (BD) and soil pH were also determined. Average soil organic carbon (SOC) content was observed to be higher in pasture (6.65 g kg-1) followed by forest (6.50 g kg-1), horticulture (5.76 g kg-1), agriculture (4.88 g kg-1), and degraded land (4.47 g kg-1). Soil BD was observed significantly higher in degraded land than in other land use, which was further increasing in deeper soil profiles. Macro aggregates (>2 mm) were abundant (52.52-91.13%) in pasture soils while micro-aggregates (<0.25 mm) were abundant (23.39-35.51%) in agriculture lands. Mean weight diameter (MWD) decreased significantly with immersion in water for soil depth for various land use indicating that the soils were vulnerable to water erosion. The influence of cultivation was generally expressed by reduced water stability aggregates (WSA) of soil aggregates, hence rendering the soil more vulnerable to crusting and erosion processes. Mean weight diameter (MWD) was dominant in pasture in surface soil whereas subsurface soil was dominant in forest landuse systems. The MWD from dry structure stability (GMDd) and their corresponding wet Mean weight mean diameter (MWDw) were related significantly (r = 0. 0.999**). The difference in the MWD in dry condition and immersion in water reveals that for degraded land was subject to severe degradation compared to cultivated, agriculture and horticulture soil, while for pasture land was more degraded than forest soil. The vegetation grown soils were of better soil structural quality than degraded land or no scanty vegetation. To preserve good structure thereby reducing soil degradation, long term fallows or other farming practices that ensure maintenance of soil organic matter.

Effect of Integrated Soil Fertility Management on Crop Production: A Review

Maintaining soil fertility is one of the main factors affecting the sustainability of food production. Indiscriminate use of chemical fertilizers, coupled with neglected maintenance of the vitality of the soil and the use of destructive methods have caused loss or destruction of the existing population of soil organisms. The use of chemical fertilizer, organic fertilizer or bio fertilizer has its advantages and disadvantages in the context of nutrient supply, crop growth and environmental quality. The advantages need to be integrated in order to make optimum use of each type of fertilizer and achieve balanced nutrient management for crop growth. This review study showed that balanced fertilization using both organic and chemical fertilizers is important for maintenance of soil organic matter (OM) content and long-term soil productivity in the tropics where soil OM content is low. The basic concept underlying the ISFM is the adjustment of soil fertility and plant nutrient supply to an optimum level for sustaining desired crop productivity through optimization of the benefits from all possible sources of plant nutrients in an integrated manner. Therefore, increased attention should be being paid to developing an integrated soil fertility management that maintains or enhances soil productivity through balanced use of all sources of nutrients, including chemical fertilizers, organic fertilizers and bio fertilizers. Keywords: Chemical Fertilizer, Organic Fertilizer, Integrated Soil Fertility Management DOI : 10.7176/JBAH/9-8-01 Publication date : April 30 th 2019

Effects of Soil Management on Aggregation and Organic Matter Dynamics in sub-Saharan Africa

Maintenance of soil organic matter (SOM) is important for soil quality and agricultural productivity. However, little is known about the effects of management practices of different intensities on soil aggregation and SOM dynamics in tropical arable cropping systems of sub-Saharan Africa. We investigated the influence of land use practices and management intensity on soil aggregation and SOM dynamics across 12 long-term field experiments in eastern and western Africa. Aggregate size distribution and SOM were measured in arable systems under contrasting management intensities of high carbon, low carbon and a fallow. Aggregate stability indices and SOM were generally higher in the fallow compared to the arable systems. Fallowing and high carbon inputs in arable soils, significantly improved aggregate stability and carbon (C) and nitrogen (N) stabilization in whole soil, and in aggregate fractions. In contrast, no significant improvements in soil aggregation and C and N stabilization were found when organic inputs were either applied in low quantities or not applied at all, thus resulting in low carbon in soils. Our study showed that fallowing and long-term application of organic amendments alone or in combination with mineral fertilizers were the best among the practices tested in this study, for enhanced C and N stabilization in soils with the subsequent benefits of improving soil physical and chemical properties. These results emphasize the importance of management for sustaining soil quality. It is recommended that fallowing be an integral part of sustainable soil management strategies in these regions. Keywords: Soil aggregation, soil organic matter, carbon, nitrogen, management intensity

English

Sustaining the productive capacity of soils has raised interest in the maintenance of soil organic matter through management practices and use of crop residues. While the impact of management practices has been studied, little is done to understand how the charateristics of the residue itself impact the decomposition at the soil surface. This study relates the chemical composition and the surface area of the aboveground residue to the decomposition rates for three cultivars each of three crops: cotton, peanut and sorghum. The rates were determined by mass loss. Change in the residue specific surface area to mass loss was also measured. Findings show that after 14 days, the aboveground residue for the three crops were from the most rapid loss to the slowest: cotton (43%) > peanut (32%) > sorghum (24%). Changes in the specific surface area-to-mass ratio were from the slowest to the most rapid loss: cotton (1.60×10-4) > peanut (1.50×10-4> sorghum (1.20×10-4). Since varietal differences within crops have led to variation in decomposition rates, cultivars with slower decaying residues might be recommended for C sequestration and for erodible lands in semi-arid zones of the Sahel. Likewise, crop residues with faster decomposition rates can be recommended for soil fertility improvement. Key words: Decomposition rate, crop type, crop residue, chemical composition, specific surface area-to-mass ratio.

The monitoring of southern chernozem soil humus content with using multispectral satellite images Landsat: spatial and temporal aspects

For rational use of soils it is necessary to possess exact information on soil properties. The traditional methods of monitoring of soils and (or) their separate properties based on local, one-time supervision don’t give an adequate assessment of a current state of a soil cover it should be noted. Transition to spatio-temporal methods with use of modern geoinformation and space technologies is necessary. Remote satellite methods of soil monitoring gain fast distribution, owing to the efficiency, a certain objectivism and relative low cost now, and also because of unique opportunities of one-time coverage by the images received from big height, enough territories, big on the area. For the development of remote monitoring chernozems southern used materials of multispectral scanning multispectral camera ETM + ( «Enhanced Thematic Mapper Plus»), which is on board the satellite «Landsat-7» (data of 2006, 2010, 2012) and OLI («Operational Land Imager»), which is on board the satellite «Landsat-8»(data 2015). The information obtained from them is unified from the point of view of preservation of geometry, calibration, a covering, spectral characteristics, quality of the image and availability of data, despite various carriers of devices ETM+ and OLI. The composite image which has been received from three cloudless satellite images of spring of 2012 (three terms of shooting – 21.04, 30.04, 05.05) has allowed to make the correlation analysis of extent of influence of maintenance of organic matter in a layer of soil of 0–10 cm at a brightness with various spectral channels of the camera ETM+. Such analysis has shown that the closest connection exists between the content of soil organic matter and brightness of the second (green), the third (red) and the fourth (the neighbor infrared) spectral channels. From them three, the greatest value of correlation has dependence between the content of soil organic matter (humus) and brightness of the red spectral channel (r=-0,32). For the purpose of spatio-temporal interpretation of the equation of multiple regressions, 20 agro landscapes in different parts of the Right-bank steppe of Ukraine (The Mykolayiv district and Zhovtnevy district of the Mykolayiv oblast) have been selected. For each agro landscapes was defined content of soil organic matter in the soil using Landsat 7 satellite images taken in 2006 and in 2010 and Landsat images 8 for 2015. The made estimates of maintenance of soil organic matter have shown on processes of fast loss of humus in all layers of soil. Annual losses of soil organic matter in a layer of 0–10 cm from 2006 for 2015 have made 0,16 % in a year, in a layer of 0–50 cm of about 0,13 % in a year, and in a layer of 0–100 cm at 0,10 % in a year. The irrational structure of sown areas and distribution of wind and water erosion processes is the reason of this sad process.

Long term application of dairy cattle manure and pig slurry to winter cereals improves soil quality

Organic fertilizers (manures and slurries) applied repeatedly over many cropping seasons favourably influence nutrient recycling, maintenance of soil organic matter (SOM), and improve soil quality parameters such as soil aggregation and porosity. These aspects are particularly relevant in Mediterranean environments characterized by low SOM. This study was set up in a subhumid Mediterranean area where two different trials, devoted to winter cereals, were fertilized with dairy cattle manure (DCM) or pig slurry (PS) for a period of 12 years. One objective of this research was to evaluate the impacts of these fertilization practices on aggregate stability and SOM fractions, when compared with a mineral N fertilizer and a control (no-N) treatment. Porosity and pore shape were also studied in PS plots. The use of DCM significantly increased water stable aggregates by up to 16.4–18.0 %. Slurry addition did not affect aggregation but it increased the area occupied by pores >65 µm. Soil organic carbon (SOC) and light organic fraction (0.05–0.2 mm) increased with DCM incorporation but in PS treatments the SOC increment was non-significant. Data from DCM and PS together showed a positive and significant linear relationship between SOC (p < 0.05, R2 = 0.60), SOC light fraction (p < 0.01, R2 = 0.75) and SOC light fraction at 0.05–0.2 mm size (p < 0.01, R2 = 0.83), with water-stable aggregate. The use of animal residues (DCM or PS), applied according to an N criterion, increased available phosphorus and potassium soil content while improving yields. The enrichment of soil nutrients with DCM and PS use requires further research in order to avoid potential environmental impacts.

Effect of Good Agricultural and Environmental Conditions on erosion and soil organic carbon balance: A national case study

Since, the Common Agricultural Policies (CAP) reform in 2003, many efforts have been made at the European level to promote a more environmentally friendly agriculture. In order to oblige farmers to manage their land sustainably, the GAEC (Good Agricultural and Environmental Conditions) were introduced as part of the Cross Compliance mechanism. Among the standards indicated, the protection of soils against erosion and the maintenance of soil organic matter and soil structure were two pillars to protect and enhance the soil quality and functions. While Member States should specifically define the most appropriate management practices and verify their application, there is a substantial lack of knowledge about the effects of this policy on erosion prevention and soil organic carbon (SOC) change. In order to fill this gap, we coupled a high resolution erosion model based on Revised Universal Soil Loss Equation (RUSLE) with the CENTURY biogeochemical model, with the aim to incorporate the lateral carbon fluxes occurring with the sediment transportation. Three scenarios were simulated on the whole extent of arable land in Italy: (i) a baseline without the GAEC implementation; (ii) a current scenario considering a set of management related to GAEC and the corresponding area of application derived from land use and agricultural management statistics and (iii) a technical potential where GAEC standards are applied to the entire surface. The results show a 10.8% decrease, from 8.33Mgha−1 year−1 to 7.43Mgha−1 year−1, in soil loss potential due to the adoption of the GAEC conservation practices. The technical potential scenario shows a 50.1% decrease in the soil loss potential (soil loss 4.1Mgha−1 year−1). The GAEC application resulted in overall SOC gains, with different rates depending on the hectares covered and the agroecosystem conditions. About 17% of the SOC change was attributable to avoided SOC transport by sediment erosion in the current scenario, while a potential gain up to 23.3Mt of C by 2020 is predicted under the full GAEC application. These estimates provide a useful starting point to help the decision-makers in both ex-ante and ex-post policy evaluation while, scientifically, the way forward relies on linking biogeochemical and geomorphological processes occurring at landscape level and scaling those up to continental and global scales.

Effects of agricultural management practices on earthworm populations and crop yield: validation and application of a mechanistic modelling approach

Summary There is little consensus on how agriculture will meet future food demands sustainably. Soils and their biota play a crucial role by mediating ecosystem services that support agricultural productivity. However, a multitude of site‐specific environmental factors and management practices interact to affect the ability of soil biota to perform vital functions, confounding the interpretation of results from experimental approaches. Insights can be gained through models, which integrate the physiological, biological and ecological mechanisms underpinning soil functions. We present a powerful modelling approach for predicting how agricultural management practices (pesticide applications and tillage) affect soil functioning through earthworm populations. By combining energy budgets and individual‐based simulation models, and integrating key behavioural and ecological drivers, we accurately predict population responses to pesticide applications in different climatic conditions. We use the model to analyse the ecological consequences of different weed management practices. Our results demonstrate that an important link between agricultural management (herbicide applications and zero, reduced and conventional tillage) and earthworms is the maintenance of soil organic matter (SOM). We show how zero and reduced tillage practices can increase crop yields while preserving natural ecosystem functions. This demonstrates how management practices which aim to sustain agricultural productivity should account for their effects on earthworm populations, as their proliferation stimulates agricultural productivity. Synthesis and applications. Our results indicate that conventional tillage practices have longer term effects on soil biota than pesticide control, if the pesticide has a short dissipation time. The risk of earthworm populations becoming exposed to toxic pesticides will be reduced under dry soil conditions. Similarly, an increase in soil organic matter could increase the recovery rate of earthworm populations. However, effects are not necessarily additive and the impact of different management practices on earthworms depends on their timing and the prevailing environmental conditions. Our model can be used to determine which combinations of crop management practices and climatic conditions pose least overall risk to earthworm populations. Linking our model mechanistically to crop yield models would aid the optimization of crop management systems by exploring the trade‐off between different ecosystem services.

Nutrient Cycling and Soil Health in Organic Cropping Systems - Importance of Management Strategies and Soil Resilience

&lt;p&gt;Organic field crop systems are characterized by complex rotations with high spatial and temporal vegetative diversity, an enhanced use of legumes, and reduced external nutrient (nitrogen (N) and phosphorus (P)) use. At the same time, a core premise of certified organic agriculture is that this farming system provides benefits to soil health via enhanced microbial diversity. The following short review, drawing primarily upon selected studies from North America, examines the impact of farming systems, and various management strategies within these, on soil organic matter, N and P dynamics, and soil microbial and macrofaunal abundance and diversity. Organic cropping systems are shown to provide benefits with respect to reduced farm N and P surpluses, in combination with maintenance of soil organic matter and improved soil health. However, soil health benefits appear consistently achieved only for larger soil organisms partly due to the resilience of the soil microbial community. Recent research examining soil P dynamics and P uptake in relation to legume biological N&lt;sub&gt;2&lt;/sub&gt; fixation and bacterial and mycorrhizal community diversity provide evidence of the resilience of the soil microbial community with respect to functionality, if not diversity of microbial community composition. These latter results may challenge organic agriculture core premises of consistent benefits to soil health via enhanced microbial diversity, but in its place may lead to an improved understanding of how specific cropping practices and production system intensity overall, rather than farming system per se, influences both nutrient cycling and soil ecosystem functioning.&lt;/p&gt;

Effects of Long-Term Winter Planted Green Manure on Distribution and Storage of Organic Carbon and Nitrogen in Water-Stable Aggregates of Reddish Paddy Soil Under a Double-Rice Cropping System

In agricultural systems, maintenance of soil organic matter has long been recognized as a strategy to reduce soil degradation. Manure amendments and green manures are management practices that can increase some nutrient contents and improve soil aggregation. We investigated the effects of 28 yr of winter planted green manure on soil aggregate-size distribution and aggregate-associated carbon (C) and nitrogen (N). The study was a randomized completed block design with three replicates. The treatments included rice-rice-fallow, rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass. The experiment was established in 1982 on a silty light clayey paddy soil derived from Quaternary red clay (classified as Fe-Accumuli-Stagnic Anthrosols) with continuous early and late rice. In 2009, soil samples were collected (0-15 cm depth) from the field treatment plots and separated into water-stable aggregates of different sizes (i.e., >5, 2-5, 1-2, 0.5-1, 0.25-0.5 and <0.25 mm) by wet sieving. The long-term winter planted green manure significantly increased total C and N, and the formation of the 2-5-mm water-stable aggregate fraction. Compared with rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass, the rice-rice-fallow significantly reduced 2-5-mm water-stable aggregates, with a significant redistribution of aggregates into micro-aggregates. Long-term winter planted green manure obviously improved C/N ratio and macro-aggregate-associated C and N. The highest contribution to soil fertility was from macro-aggregates of 2-5 mm in most cases.

Desempenho de plantas de cobertura submetidas à déficit hídrico

The objective of this study was to evaluate the effect of drought on biomass of different cover crops. The experiment was conducted in a greenhouse at the experimental campus of the Federal University of Piaui (UFPI), on soil classified as Yellow Latosol dystrophic. The treatments were composed by five species of cover crops ( Brachiaria brizantha cult. Xares; Pennisetum glaucum cv. ADR 300; Brachiaria ruziziensis ; Mucuna aterrima ; Pennisetum. glaucum cv. ADR 7010) and four irrigation intervals levels (2, 4 6 and 8 days). Independent of the levels of water deficit, the highest biomass were obtained in species B. brizantha , B. ruziziensis , P. Glaucum cv. ADR 300 and ADR 7010. There was greater tolerance of M. aterrima levels of water deficit. The species of B. brizantha and B . ruziziensis accumulated 70% of the dry weight of tops of sheets, while P. glaucum cv. ADR 300 and ADR 7010 accumulated 60% of the stem. Even with reductions in biomass under water deficit conditions, the species B. brizantha and B. ruziziensis have potential for soil cover and P. glaucum residues as a source for the maintenance of soil organic matter.

Simulated Impacts of Crop Residue Removal and Tillage on Soil Organic Matter Maintenance

Cellulosic biofuel production may generate new markets and revenue for farmers. However, residue removal may cause environmental problems such as soil erosion and soil organic matter (SOM) loss. The objective of this study was to determine the amounts of residue necessary for SOM maintenance under different tillage and residue removal scenarios for corn–soybean [Zea mays L.–Glycine max (L.) Merr.] and continuous corn rotations for a site in west‐central Minnesota. We employed a process‐based model (CQESTR) to evaluate management practices and quantify SOM changes over time. Results showed that conventional tillage resulted in SOM loss regardless of the amount of residue returned. Under no‐till, residue amount was important in determining SOM accumulation or depletion. For the upper 30 cm of soil, average annual rates of 3.65 and 2.25 Mg crop residue ha–1 yr–1 were sufficient to maintain SOM for corn–soybean and continuous corn rotations, respectively. Soil OM in soil layers below 30 cm was predicted to decrease in all scenarios as a result of low root inputs. When considered over the upper 60 cm (maximum soil depth sampled), only continuous corn with no‐till was sufficient to maintain SOM. Results from this work are important because they show that, for these management scenarios, no‐till management is necessary for SOM maintenance and that determining whether SOM is accumulating or declining depends on the soil depth considered. At current yields observed in this study area, only continuous corn with no‐till may generate enough residue to maintain or increase SOM.

Influence of plant residues, farm yard manure and inorganic fertilizers on soil N and P mineralization and growth ofAbelmoschus esculentusLinn.

Management of crop residues can have important implications apart from the desired maintenance of soil organic matter and improving plant growth. In order to test this hypothesis, field experiments were conducted to evaluate the effects of plant residues, farm yard manure and inorganic fertilizers on soil N and P mineralization and growth of Abelmoschus esculentus Linn. A randomized complete block design consisting of nine treatments including the control was used with three replications each. ‘Okra’ was selected as the test crop. The source of N, P and K was urea (containing 45% N), superphosphate (16% P), muriate of potash (60% K). The application of full NPKand half NPK doses recorded 72 and 84 germination percentage. Nevertheless, the plots amended with half NPK and full NPK doses did not significantly (F= 0.067, n< 0.05) increase the growth of crop. The regression analysis of shoot and root biomass shows positive correlation in each treatments.The study revealed that NPK amended soils showed two times more fruit biomass production than the plant residue amended soils. Net N mineralization in different treatments ranged from 0.112 to 0.410 mg g−1 day−1. N mineralization significantly varied among the plots with inorganic fertilizers having the highest mineralized N followed by residues applied soils and controls the least. On the other hand, phosphorous mineralization was higher in fertilizer amended soils. Over all, crop residue management with supplementary chemical fertilizer loading could help have better yield response under ‘`business as usual’ climate scenario.

Crop response and soil fertility as influenced by green leaves of indigenous agroforestry tree species in a lowland rice system in northeast India

Field experiments were conducted during rainy seasons of three consecutive years (2008–2010) to study the effect of green leaf manuring on dry matter partitioning and productivity of lowland rice (Oryza sativa L.). Green leaves of five indigenous agroforestry tree species viz., Erythrina indica, Acacia auriculiformis, Alnus nepalensis, Parkia roxburghii, and Cassia siamea were treated at 10 t ha−1 on fresh weight basis in rice fields and compared with recommended N–P2O5–K2O (80:60:40 kg ha−1) and control treatments. During 2008–2009 year, yield attributes and rice yield were greater in NPK plots as compared to the green-leaf manured ones. However, in the third year, green leaf manuring (except that of Alnus) surpassed even the recommended N–P2O5–K2O treatment in terms of dry matter production and yield; better response was however observed with Erythrina. The soil available N after final harvest increased by ca. 14–20 % in Alnus and Erythrina treated plots as compared to the control. Over all, it could be said that management of plant residues can have long-term implications apart from the desired maintenance of soil organic matter and improving crop yield.