Clover Straw Research Articles

Measurements of Electromagnetic Radiation Propagation through Biomaterial Samples Based on Harvest Residues

The aim of this research was to determine the efficiency of electromagnetic (EM) radiation absorbers based on biomaterials from harvest residues (soybean straw, wheat straw, and clover straw) for the additional protection and/or construction of residential buildings. To determine their protective properties, the transmission parameter S21 was measured through harvest residues in the frequency range from 300 MHz to 5 GHz. Important parameters of the tested samples included sample type, sample thickness, and humidity. The measurement results showed that the transmission parameters decreased with an increase in the sample thickness, moisture, and frequency. Regarding this type of substrate, soybean straw showed the lowest values of parameter S21 for all measurements except for the case of the highest amount of moisture (34.48%), for which clover straw showed the lowest value of the transmission parameter. The greatest reduction in the S21 transmission parameter was 43.80 dB for a soybean sample of 300 mm thickness at a frequency of 4.93 GHz. These tests were performed on samples that were not additionally structured (additives, pressing, additional shredding, etc.), so it was possible to optimize their structure and conduct further research.

Mercerization of Agricultural Waste: Sweet Clover, Buckwheat, and Rapeseed Straws

This research presents the alkali treatment effect on three types of agricultural residues: sweet clover (SCS), buckwheat (BS), and rapeseed straws (RS). The aim of the study was to find the optimal treatment conditions for each straw type, and to assess the potential of sweet clover straw as reinforcement for polymer composites in comparison to buckwheat and rapeseed. The straws were ground and treated for 15, 30, and 60 min using NaOH at concentrations of 2, 5, and 10%. To investigate the treatment results on the SCS, BS, and RS fibers, Fourier transform infrared spectroscopy, scanning electron microscopy, optical microscope, X-ray diffraction, and thermogravimetric analysis were used. Results indicate that the optimal room-temperature alkaline-treatment conditions of SCS fibers were the same as those for RS treated with 2% NaOH solution for 30 min. These conditions were milder in comparison to those used for the treatment of BS: 60 min in a 5% NaOH solution. During the treatment, noncellulosic substances were largely removed, and the aspect ratio of the fibers was increased, and the destruction temperature, crystallinity, and morphology were also affected. Consequently, SCS has promising potential for use in polymer composites.

Use of available crop by-products as alternative bedding materials to wheat straw for rearing broilers

The provision of suitable bedding for rearing broilers is an ongoing challenge for poultry producers. The aim of the present study was to evaluate the effect of using different types of crop residues as alternative bedding materials to wheat straw on growth performance, carcass traits, health, and welfare of broilers; moreover, the effects on the bedding and air quality were analyzed. We randomly assigned 180 1-day-old chickens (Cobb 500) across six bedding groups (three replicates of 10 birds each). Chickens in all groups were reared under similar housing conditions. Chickens of one group were reared on a wheat straw bedding (control), whereas those of the remaining five groups were reared on clover straw, cornstalk chips (CS), sugarcane top chips, chopped palm spines (CPS), and corn ear husks. Cornstalk chip and chopped palm spines were associated with the lowest (P < 0.05) ammonia concentrations compared with the remaining beddings. The mean values of bedding moisture percentage (P < 0.05), caking score, and ammonia concentrations (P < 0.05) were decreased with 6-week-old broilers reared on cornstalk chips. At 6 weeks, wheat straw, clover straw, sugarcane top chips and corn ear husks resulted in higher (P < 0.0001) BW and average daily gain compared with CS and CPS. Broilers reared on clover straw bedding showed the best FCR during 4–6 weeks of age (P < 0.01), and those kept on clover straw and sugarcane top chips exhibited the best (P < 0.01) feed conversion ratio (1.61 and 1.64, respectively) during 0–6 weeks of age. The carcass dressing yield, airborne dust concentration, bedding pH, and bacterial counts did not differ among the different bedding materials. The proportions of the drumsticks, gizzards, and abdominal fat of 6-week-old broilers were affected by bedding type (P < 0.05); but the differences among the bedding treatments were small. The mean incidence of footpad dermatitis and breast blisters was significantly less using clover straw. Broilers reared on chopped palm spine had the highest (P < 0.05) heterophil/lymphocyte ratio when compared with their counterparts. Conclusively, using clover straw or cornstalks as an alternative bedding material may be a beneficial strategy and should be highly recommended for rearing broilers.

A case of diquat poisoning in pigs

Diquat is a bipyridyl compound which belongs to the group of herbicides. Its activity is based on the liberation of the superoxide anion radical and, subsequently, hydrogen peroxide, leading to tissue destruction by oxidative stress. Acute poisoning is associated with high mortality within several hours to a few days. The reported case of poisoning occurred on a commercial farm. The fattening pigs of the Landrace and Large White breeds were affected. The pigs were kept on a deep litter. Reglone (active ingredient diquat dibromide, 200 g/l) was used on the farm fields to desiccate the clover crop. The dry clover straw was harvested and stored for approximately a month and then used as a litter. In total, 50 pigs were affected. The onset of the poisoning was very fast. Within eight hours after the litter administration, 20 animals died. The only clinical sign seen was severe haemorrhagic dermatitis. The pathological examination revealed acute superficial haemorrhagic dermatitis on the belly, the snout and the ears of the affected pigs. Hyperaemia of the tonsils, pharynx and oesophagus was diagnosed, as well as a pronounced hyperaemia of the stomach fundus. In the distal part of the trachea, there was a dense, white foam. The lungs were congested, with focal emphysema. The liver was slightly hyperaemic. The histological examination revealed a massive haemostasis in liver and diffuse acute polymorphonuclear hepatitis. The other organs were without changes. The examination revealed acute poisoning caused by the large body surface areas contacting with a toxic substance. The pigs that survived were immediately removed to a non-contaminated area. The changes on their skin were not so extensive compared to the dead ones. Within 5–7 days after the exposure to diquat, the skin lesions healed.

EFFECT OF MINERAL, ORGANIC AND BIO FERTILIZATION ON WHEAT PRODUCTION IN TWO DIFFERENT SOILS

Biological experiment was conducted in the clay and sandy soils to study the effect of inorganic, organic and bio fertilization on growth and yield components as well as N, P and K- uptake by wheat plants. Ammonium sulphate (N) was added at the rates of 25 [50% the recommended dose (RD)] and 50 (100% RD) mg N kg-1 soil, while ordinary superphosphate (P1) and rock phosphate (P2) were applied at the rates of 9.72 (50% RD) and 19.44 (100% RD mg P kg-1 soil. Potassium sulphate (K1) and feldspar (K2) were added at the rates of 20.8 (50% RD) and 41.5 (100% RD) mg K kg-1 soil. The organic materials i.e. clover straw (CS), sunflower seed teflon (ST) and banana peel (BP) were added at a rate of (0.5%). Some wheat grains were inoculated by biofertilizers i.e. nitrobein (nit), phosphate dissolving bacteria (PDB) and potassiumage (Pot). The results showed that the treatments of [50% RD (NP1K1) + CS + ST + BP + Nit + PDB + Pot] gave the greatest values of the straw and grains dry weight, biological yield and harvest index, N-uptake by grains and P- and K- uptake by straw and grains if compared to the other treatments in both soils under study. Wherease the highest 1000 grains weight was observed with the treatment of [50% RD (NP2K2) + CS + ST + BP + Nit + PDB + Pot] in the clayey soil and [50% RD (NP1K1) + CS + ST + BP] in the sandy soil compared to the other treatments. The greatest values of N- uptake by straw were recorded with treatments of [50% RD (NP1K1) + CS + ST + BP] in the clayey soil and [50% RD (NP1K1) + CS + ST + BP + Nit + PDB + Pot] in the sandy soil compared to the other treatments. Finally, it could be concluded that the use of 50% of the recommend dose of the most mineral fertilizers (NP1K1) mixed with organic materials (CS + ST + BP) and biofertilizers (Nit + PDB + Pot) may reduce the mineral fertilization (NP1K1) dose, production cost and environmental contamination.

THE EFFECT OF RATIONS CONTAINING DRUMSTICK TREE (MORINGA OLEIFERA) BY PRODUCT ON GROWTH PERFORMANCE YOUNG POST-WEANING RABBITS

The study aimed to investigate the effect of using different dietary levels Moringa by product as a partial replacement (0, 25, 37.5 and 50%) for clover straw. Results indicated that the chemical composition of Moringa Oleifera by product value contained high protein, DM, OM and NSC and lowest contents other values compared to clover hay, values were recorded with of NFE, CF and P. The study rations of containing different dietary levels Moringa by product on growth performance, digestibility coefficient of nutrient, nutritive value, cecum activity, carcass characteristics, quality meat and some blood plasma constituents of growing New-Zealand White. The chemical composition of these ration has nearly similar CP, EE, CF and digestible energy. Growth performance of the experimental groups could be noticed that the carcass weight and total edible parts increased (P<0.05) with replacing Moringa olifera by product meal instead clover hay at level 25%, 37.5% and 50% compared to the control ration, the values of carcass weight were 940.92, 966.83 and 1024.33gm , the total edible parts were 52.22, 51.83 and 53.44 gm, respectively .The best results were recorded with R4 containing Moringa by product meal 50%., the significantly improved up to rate 5.25%. This observation may reflect the relatively higher feed intake by rabbits on the Moringa by product meal diets resulting in higher daily weight gain. The values of ash and EE were insignificant effect in meat. The values of moisture, dry matter and crude protein were significant between values, the best results crude protein and dry matter meat recorded with R2 compared with control R1. The total period from (6-13 weeks) observed the total feed conversion ratio values significant increase between rations and the best feed conversion ratio recorded with R4 (3.38g/feed /gain)). The result indicted to the best ration with replacement moringa by product meal by 50%. The results of digestibility coefficient were significant differences among three tested rations compared with control for indicated that adding Moringa olifera by product roughage meal at 25%, 37.5% and 50% significantly improved (P<0.05) digestibility coefficient. while the best improved significant values were recorded with 50% R4 containing moringa by product followed by R3 more than other R2 and control (R1). In rabbit diet (R4) recorded the best results cell-wall constituent digestibility data and the highest nutrient digestibility. The highest content Moringa by product meal (50%) showed the highest TDN (67.41%) and DCP (12.27%) and significant increased caecum weight, caecum length, caecum PH and total volatile fatty acids (TVFA,s) caeca juice. There was insignificant trend towards a reduction in the cholesterol of level moringa R4 by (3.13%) compared with control (R1). This reduction in serum may be suggest a general decline in lipid mobilization. It may be suggested then that, moringa leaf meal diets can reduce serum cholesterol, hence assisting in the reduction and deposition of cholesterol in the muscles. The economic efficiency of R4was higher by 11.31 %, total revenue increased by 4.45%, Net revenue by 10.35%, feeding cost was 1% slightly lower compared with control rations. No mortality of rabbits was recorded during the study by product

Optimization of Xylanase Production from Some Agro-lignocellulosic Wastes by Aspergillus niger Via Solid State Fermentation

Extracellular xylanase production by A. niger was studied under solid-state fermentation using six agricultural wastes individually (wheat bran, rice husk, corn cobs, rice straw, clover straw and wheat straw) as well as fifteen treatment represent different combinations of the above agro-lignocellulosic wastes. The best substrate was the combination of wheat bran and clover straw. The initial moisture content, additive carbon source, additive nitrogen source, initial pH of the culture, incubation temperature and inoculum size affected the production of xylanase. The optimal fermentation medium was at 80% of initial moisture and composed of 5 g WB+CS (1:1 w/w) supplemented with 1% (w/w) of xylan and 1% (w/w) of (NH4)3PO4 and inoculated by adding 1 ml of spore suspension containing 2x105spores/ml. Xylanase production reached a peak of 1294.15 IU/gdw after 7 days of incubation at 35 °C under SSF. The produced enzyme has maximum activity at 70 oC and pH 5.5. Addition of 10 mM FeSO4 and 5mM of KCl, CaCl2 and MnCl2 to the reaction mixture enhanced xylanase activity to 127.46, 118.86, 115.76 and 111.15%, respectively. A. niger xylanase showed superior heat and pH tolerance, it remained 86.47 and 76% of its activity after 60 min of incubation at 70 oC with and without 10 mM CaCl2.The enzyme showed more stability in a pH ranged from 4 to 5 retaining more than 75% of its original activity, therefore it may have significant applications in biofuel and paper industries.

Effect of Residues Agricultural Wastes on the Productivity and Quality of Pleurotus colombinus L. by Using Polyethylene Bags Wall Technique

The investigation studied effect of residues of agriculture wastes by using polyethylene bag wall technique on Pleurotus colomninus L. srain 99 yield and their quality during both successive seasons of 2013/2014 and 2014/2015. The results indicated that different substrate formulas such as clover straw, wheat straw, sawdust, corn cob, soybean straw and rice straw gave significant differences characteristics of fruiting bodies, yield, biological efficiency, nutritional composition and mineral contents. The highest number counted fruit/bag was obtained from rice (14 and14.33 fruit/bag) and wheat straw (14 and 13.33 fruit/bag) in both seasons respectively. However, the elevated yield weight (288.10 and317.33 g/bag and biological efficiency (82.26 and 90.63 %) was found from soybean straw in both seasons respectively. The six substrates exhibited the suitable cultivation media and their effectiveness on physical characteristics such as stalk length, stalk diameter and cap diameter. Highest content of nitrogen (2.50 and 2.57 g/100g) phosphorus (2.50 and 2.57 g/100g) potassium (2.54 and 2.63 g/100g) was achieved from clover straw in both seasons respectively. While the elevated contents of protein (7.41 and 7.24 g/100g), carbohydrates (31.40 and 33.34 g/100g) and energy (158.17 and165.91) obtained from soybean straw in both season respectively. Wheat straw substrate gave an increment fat (0.42 and 0.42 g/100g) and fiber content (5.42 and 5.60 g/100g in both season respectively, on the other side corn cob substrate gave the highest ash content (9.11 and 9.30 g/100g in both seasons respectively. The raw and spent substrates were analyzed for their nutritional value composition.

Influence of Agricultural Wastes and Incubation Period on Aggregate Stability in Sandy Soil

A laboratory experiment was conducted to examine the influence of various organic materials on soil aggregate stability of sandy soil collected from Al-Bustan region, Egypt. The study involved five treatments: control, incorporating 1% of wheat straw, 1% clover straw, 1% mixture of wheat & clover, and 1% chicken manure into sandy soil on the basis of air dry weight. Soil samples were incubated at field capacity for 7, 14, 28, 42 and 56 days at 30 Co±1. Water-stable aggregate size distribution (1.19-2, 0.5-1.19, 0·25–0.5 mm) was determined through wet sieving. The organic wastes treatments improved soil aggregate stability compared with control treatment. The changes in aggregate stability indices (mean weight diameter (MWD), Structure coefficient (Cr), detachability index (DI), percentage of aggregate destruction (PAD) and Wet aggregate stability (WAS) were determined and calculated weekly over the periods of incubation. The application of organic wastes significantly increased all aggregate stability indices compared to the control treatment except PAD. Soil aggregate indices had significant positive correlations between each other. MWD, Cr, WAS and DI values were the highest in chicken manure treatment, while the PAD values were the lowest. Disaggregation occurred in all treatments after 28 days of incubation. Polynomial function brought higher correlations between MWD, Cr, DI and PAD vs. the incubation period of sandy soil amended with organic wastes. The Cr, DI and PAD vs. MWD produced linear relationship with high correlations.

REPLACEMENT OF MORINGA STEMS INSTEAD OF CLOVER STRAW WITH OR WITHOUT MULTI ENZYMES (CAPLIX) IN GROWING RABBIT DIETS

A total number of 72 New Zealand White (NZW) growing rabbits of mixed sex, 6 weeks old of about 500±13.75 g average body weight were used to study the effect of different levels of Moringa stems without or with supplementation of caplix enzyme on rabbit performance, nutrients digestibility coefficient, caecum activity, carcass characteristics and economic efficiency. Rabbits were divided into 6 treatments; each containing 12 rabbits in 4 replicates (3 rabbits in each). Three substitution levels of Moringa stems, as well as, two levels without or with caplix were used in 3×2 factorial arrangement. Moringa stems levels were zero (control), 25 and 50% instead of clover straw of the control diet, while the levels of caplix were 0 or 0.05% of diet. The experimental period was extended to 8 weeks. These results obtained indicated that, replacing Moringa stems for clover straw at 25 and 50% in rabbit diets significantly (P<0.05) improved CP, EE, CF, NDF, ADF and ADL digestibility as will as DCP and TDN values compared to the control group. Also, adding caplix to rabbit diets improved (P<0.05) these nutrients digestibility as compared to the groups fed diets without caplix. Replacing Moringa stems by clover straw at 25 and 50% or adding caplix to rabbit diets resulted in an improvement (P< 0.05) of caecum pH and an increase (P<0.05) in caecal VFAS concentration. There were significant (P<0.05) increases in average daily BWG and significant (P<0.05) improvement in FCR with either replacing Moringa stems at a level of 25% or adding caplix to rabbit diets. Replacing Moringa stems by clover straw at 25 and 50% or adding caplix to rabbit diets increased (P<0.05) dressing %, edible giblets% and total edible parts% in comparison to the control group. While there were insignificant differences in contents of moisture, CP and EE% among the different tested experimental groups. Replacing Moringa stems by clover straw at all tested levels in rabbit diets either without or with caplix increased the economic efficiency as compared to the control group. Conclusively, these results showed that Moringa stems can be used instead of clover straw (up to 50%) in growing rabbit diets with caplix (0.05%) without negative effects on growth performance under Egyptian environmental conditions.

Comparison of postharvest practices used for cereal straw decomposition in a clay loam soil

ABSTRACTDuring 2008–2011, model field experiments were carried out at the Joniškėlis Experimental Station of Lithuanian Research Centre for Agriculture and Forestry on a clay loam Endocalcaric Endogleyic Cambisol. The study was aimed to establish the comparison of various postharvest practices (mineral nitrogen fertiliser alone or together with a bioactivator Penergetic k, livestock slurry, red clover biomass and straw incorporation in the soil by a stubble cultivator at a 10 cm depth) on the acceleration of the initial (nine-month period) decomposition of winter wheat straw. During this period, straw mass decomposition intensity was 20.7–29.1%, carbon (C) concentration decreased by 6.5–22.8%, while an increase in nitrogen (N) by 1.1–2.2 times was observed. The highest straw decomposition rate was recorded when after straw incorporation autumn was warm and humid. That year straw mass C to N ratio (C/N) was 38–46. Under less-favourable autumn conditions, the highest decomposition of straw was achieved, having applied mineral N (with and without Penergetic) and livestock slurry and having incorporated the straw in the soil (C/N = 40–55). A slower decomposition rate was observed for the straw spread on the soil surface with mineral N addition or on undersown red clover.

Batch production of Pyranose 2-oxidase from Trametes versicolor (ATCC 11235) in medium with a lignocellulosic substrate and enzymatic bleaching of cotton fabrics

The aim of this work was to determine new, different and low-cost substrates that can be used for enzyme production from the white rot fungus Trametes versicolor (ATCC 11235) by taking advantage of the broad substrate specificity of pyranose 2-oxidase. In this report, we investigated the production of pyranose 2-oxidase from T. versicolor (ATCC 11235) using ten different agricultural residues such as clover straw, almond shells, hazelnut cobs, grass and others. Pyranose 2-oxidase activity was determined as 2.332 U/g at the 9th day in a submerged culture containing clover straw and tap water shaken at 150 rpm and 26°C, and the optimum clover straw concentration was determined to be 12 g/l. The effects of different glucose, nitrogen and phosphate sources on the production of pyranose 2-oxidase were studied in the clover straw medium. Analyses of biomass, protein, reduced sugar and nitrogen concentrations were also monitored in a clover straw medium that did not contain carbon or nitrogen and phosphate sources under the parameters determined. The produced pyranose 2-oxidase was used for improving the properties of cotton fabrics.

Effect of ecologically-based weed management strategies on weed community and diversity in hilly tea plantations

Ecologically controlling weeds does not only reduce consumption of soil water and nutrient,but also avoid or reduce application of chemical herbicides.Two ecologically-based weed management strategies based on pre-evaluation and competition of niche,straw mulching and white clover intercropping,were conducted in hilly tea plantations in 2005 and 2006,with clean tillage as the CK.Characteristics of weed community,including weed abundance,dominance,evenness,biomass and mean height were investigated via multi-sampling in small plot and the effects of two ecologically-based weed management strategies were compared with the clean tillage.About 16 families and 31 species of weeds are identified in the study.In April,the dominant weed species are those growing slowing with low biomass and lower than 30 cm.In July and September,the abundance (Pi) of malignant weed in CK respectively reaches 0.788 and 0.759,while that in straw mulching treatment is respectively 0.256 and 0.420,and a lower malignant weed occurrence frequency is found in white clover intercropping treatment with Pi0.050.Weed richness,species diversity and evenness under straw mulching treatment are all higher than those under CK,though the dominant concentration index is lower than that of CK in spring,summer and autumn.Total number,biomass in spring,summer and autumn,and mean weed height in summer and autumn under white clover intercropping treatment are lower than those under the control.The two ecologically-based treatments have a favorable effect on weed control than the clean tillage.It therefore implies that white clover intercropping and straw mulching are effective ecological weed control measures.

New and different lignocellulosic materials from Turkey for laccase and manganese peroxidase production by Trametes versicolor

AbstractIn the present study, the production of laccase (Lac) and manganese‐dependent peroxidase (MnP) by the white‐rot fungus Trametes versicolor grown in submerged cultures with different agricultural residues was investigated. The lignocellulosic materials studied were almond shells, hazelnut husks, sunflower stems, clover straw and hazelnut cobs, because they are common agricultural wastes in Turkey. Among the different lignocellulosic materials studied, hazelnut cobs provided the highest Lac and MnP activities (47.09 and 109.21 U/L, respectively). The optimum conditions were determined for Lac and MnP production in submerged cultures of T. versicolor by using hazelnut cobs as substrate. For Lac production, the optimum incubation time, hazelnut cob concentration, pH, and shaking rate were found as 4 days, 2% w/v, 6.0 and 130 rpm, respectively. For MnP production, the optimum incubation time, hazelnut cob concentration, pH and shaking rate were found as 5 days, 2% w/v, 6.0 and 90 rpm, respectively.

DISTRIBUTION AND TRANSFORMATION OF PHOSPHORUS FORMS IN SOIL AFTER LONG-TERM APPLICATIONS OF P FERTILIZER AND CROP RESIDUES

Two rates of crop residues (-CR and +CR) and six rates of P fertilizer (0, 100, 200, 300, 400, and 500 kg superphosphate fed-1) were applied each growing season (corn and clover) in a long-term field experiment started at the Experimental Farm of Assiut University, Assiut, Egypt. The crop residues were added to the soil at the end of each growth season at rates of 5.45 and 3.71-ton fed-1 corn stover and Egyptian clover straw. The response of soil P fractions to both CR and superphosphatr fertilizer was small at the very beginning of the experiment, however it became more pronounced starting from the year 1999 up to the year 2003. Resin-P accounted for 0.81- 0.93%; and 1.30- 1.52% of total P in soil after 5 and 16 years of continuous application of CR and SP, respectively.At zero level of SP and no addition of CR the resin-P fraction was markedly decreased from 6.5 to 5.65. The size of inorganic (Pi) and organic (Po) phosphorus forms of the NaHCO3 fractions were increased with the continuation of applying the P fertilization management for 16 years and ranged from 2.73 to 3.13 and from 1.84 to 2.19 for Pi and Po forms, with and without crop residues, respectively. Five years after continuous application of SP and without application of CR, the relative concentrations of NaOH-Pi and NaOH-Po increased from 3.69 to 4.44% and from 1.60 to 2.00% of total P, respectively. Also, increasing the application level of SP from zero (P0) to 500 kg SP fed-1 (P5) each growth season for five years increased the HCl-P and residual-P fractions linearly and significantly. The path analysis showed that both resin-Pi and NaHCO3-Pi were mainly and directly affected by P fertilization. In soil that received P fertilization management with CR, resin-P was largely controlled by added-Pi, NaHCO3-Pi and HCl-P fractions.

Distribution and fate of 13C-labeled root and straw residues from ryegrass and crimson clover in soil under western Oregon field conditions

Annual ryegrass (Lolium multiflorum Lam.) and crimson clover (Trifolium incarnatum L.) were pulse-labeled with 13C-CO2 in the field between the initiation of late winter growth (mid-February) and through flowering and seed formation (late May). Straw was harvested after seed maturation (July), and soil containing 13C-labeled roots and root-derived C was left in the field until September. 13C-enriched and 13C-unenriched straw residues of each species were mixed in factorial combinations with soil containing either 13C-enriched or 13C-unenriched root-derived C and incubated in the field for 10 months. The contributions of C derived from straw, roots, and soil were measured in soil microbial biomass C, respired C, and soil C on five occasions after residue incorporation (September, October, November, April, and June). At straw incorporation (September), 25–30% of soil microbial biomass C was derived from root C in both ryegrass and clover treatments, and this value was sustained in the ryegrass treatment from September to April but declined in the clover treatment. By October, between 20 and 30% of soil microbial biomass C was derived from straw, with the percentage contribution from clover straw generally exceeding that from ryegrass straw throughout the incubation. By June, ryegrass root-derived C contributed 5.5% of the soil C pool, which was significantly greater than the contributions from any of the three other residue types (about 1.5%). This work has provided a framework for more studies of finer scale that should focus on the interactions between residue quality, soil organic matter C, and specific members of the soil microbial community.

Carbon flow from 13C-labeled straw and root residues into the phospholipid fatty acids of a soil microbial community under field conditions

To better understand how residue quality and seasonal conditions influence the flow of C from both root and straw residues into the soil microbial community, we followed the incorporation of 13C-labeled crimson clover ( Trifolium incarnatum) and ryegrass ( Lolium multiflorum) root and straw residues into the phospholipid fatty acids (PLFA) of soil microbial biomass. After residue incorporation under field conditions in late summer (September), the 13C content of soil PLFA was measured in September, October, and November, 2002, and April and June, 2003. Multivariate non-metric multidimensional scaling techniques showed that the distribution of 13C among microbial PLFA differed among the four primary treatments (ryegrass straw and roots, clover straw and roots). Regardless of treatment, some PLFA remained poorly labeled with 13C throughout much of the study (16:1ω5, 10Me17:0; 0–5%), whereas other PLFA consistently contained a larger percentage of residue-derived C (16:0; 18:1ω9, 18:2ω6,9; 10–25%). The distribution of residue 13C among individual PLFA differed from the relative contributions of individual PLFA (mol%) to total PLFA-C, suggesting that a subset of the soil biomass was primarily responsible for assimilating residue-derived C. The distribution of 13C among soil PLFA differed between the sampling times, indicating that residue properties and soil conditions influenced which members of the community were assimilating residue-derived C. Our findings will provide the foundation for further studies to identify the nature of the community members responsible for residue decomposition at different times of the year, and what factors account for the dynamics of the community involved.

Temporal changes in mineralization and immobilization of N during degradation of plant material: implications for the plant N supply and nitrogen losses

Economical and ecological criteria for optimal N fertilization are inherently in conflict, largely due to lack of precise predictions of nitrogen availability as a function of agronomic practice and weather conditions. This problem is particularly pronounced in organic farming, where plant N supply depends on microbial mineralization of organic N such as ‘green manure’. In the present paper, N dynamics after incorporation of a mixture of a green manure material (undersown white clover) and barley straw was investigated in laboratory and field experiments. Nitrogen flows in the soil–plant system were further analyzed with simulation models (COUP: heat and water transport model, SOILN_NO: soil nitrogen model). Our laboratory experiments showed that the incorporation of a mixture of N-rich white clover material and N-poor barley straw created a transient accumulation of clover derived inorganic N during the first period. Thereafter, microbial N demand during straw C utilization resulted in net immobilization of most of the clover derived inorganic N. As a consequence, the synchronization between net N mineralization and plant N uptake would be better by spring than autumn incorporation. This was largely confirmed both by measurements and simulations. However, the expected benefit of spring incorporation (ploughing) was counteracted by a large loss (36%) of clover material due to freeze/thaw damage and subsequent surface runoff during the winter. Such winter loss is likely to be a rare phenomenon, however.The results supported our hypothesis that net inorganic N accumulation due to degradation of a clover–straw mixture is transient and that spring incorporation of undersown clover gives a better coincidence of N availability and N uptake by a subsequent crop than does autumn incorporation. Model scenarios showed that ploughing as late as possible in autumn appears to be a good alternative to spring ploughing with regard to N leaching, but early autumn ploughing should be avoided.The study shows that the timing of agronomic operations are important, not only for determining the fraction of inorganic N lost by leaching, but also for the fraction assimilated by microorganisms. In effect, the plants and the microorganisms compete for the same nitrogen, and the success of the plants depend on a proper synchronization.

Evidence for recycling of N from plants to soil during the growing season

In spite of the known below-ground biomass production of plant roots that concurrently introduce significant amounts of carbon and nitrogen into the soil, the effects of these inputs on N cycling in the soil–plant system are seldom considered. Here, we report on two field experiments carried out between 1995 and 1997 at the FAM Research Station Scheyern: (1) a N-turnover experiment to determine the N fluxes derived from 15N-labeled clover residues incorporated into the plough layer of defined plots, and (2) a root production experiment to assess the above (shoot) and below ground (gross and net root) biomass production of winter wheat in different fields, but nearby the 15N plots. An initial 50% decrease in soil organic 15N at 0–20-cm soil depth was recorded between fall, 1996 (incorporation of clover straw) and spring, 1997 (138 days after incorporation), which was then followed by a period of stability in 15N levels in the soil organic N until the harvest of winter wheat (286 days after incorporation). This stability may be explained in two ways: (a) actual stability of clover-derived 15N remaining in the second phase, e.g., due to recalcitrant compounds or microbial immobilization; or (b) apparent stability, e.g., because the actual mineralization of clover-derived 15N in the soil was compensated by secondary inputs of organic 15N (recycling). Further results showed that the first explanation was unlikely, as (1) between 138 and 286 days after clover incorporation, the mean 15N signature in soil mineral N was 2.1 at.%, indicating a persistent mineralization of clover residues; and (2) a decrease in soil microbial biomass 15N occurred in the second phase, indicating a continued N turnover in the soil. The amount of clover-derived 15N accumulated below the plough layer at 20–110-cm soil depth (11.5%) between early spring and the harvest of wheat also corroborated the return of mineralized 15N into the soil being due to the root N inputs by winter wheat. Based on the depth distribution of winter wheat net root biomass (root production experiment) and on soil organic 15N depth distribution ( 15N-turnover experiment), the root N input into soil was estimated to be 282 kg ha −1, equivalent to 54% of total net N assimilation of winter wheat. Thus, the results of this study give substantial evidence for a N loop between soil and growing plants, whereby a part of the net mineralized N taken up by plants is continuously returned into the soil by their roots. The implications of this N loop for the interpretation of 15N experiments and for plant nutrition are discussed.

Palha de trevo vesiculoso (Trifolium vesiculosum Savi cv. Yuchi) como substituto da silagem de milho na alimentação de novilhos confinados

O experimento teve como objetivo avaliar a utilização da palha de trevo vesiculoso como substituto parcial da silagem de milho, na fração volumosa da dieta fornecida para novilhos confinados, sendo testados os seguintes níveis de substituição: T0 constituído por 100% de silagem de milho; T25 constituído por 75% de silagem de milho mais 25% de palha de trevo vesiculoso; T50 por 50% de silagem de milho mais 50% de palha de trevo vesiculoso e T75 constituído por 25% de silagem de milho mais 75% de palha de trevo vesiculoso. O teor de concentrado na dieta oferecida foi de 32,5%. As dietas foram fornecidas durante 112 dias para novilhos com peso e idade inicial de 265 ± 1,65kg e 18 meses, respectivamente. Os dados foram submetidos à análise de regressão para nível de substituição (NS) de silagem de milho por palha de trevo vesiculoso na fração volumosa da dieta. O consumo voluntário de matéria seca (CMS) em kg de MS/100kg PV (CMSP) ou em g/kg PV0,75 (CMSUTM) decresce linearmente à medida que aumentou o nível de palha de trevo. O consumo de energia digestível diário expresso em Mcal/100kg PV (CEDPV) também decresceu linearmente conforme a equação: CEDPV = 7,22905 - 0,025941 NS. O ganho de peso médio diário (GMD) observado foi de 1,25; 1,18; 1,07 e 1,01, respectivamente. A análise de regressão mostrou que o aumento de uma unidade percentual de substituição de silagem de milho por palha de trevo provocou um decréscimo de 3,47g no GMD e piorou a conversão alimentar em 0,017 unidades. Apesar de causar uma redução no desempenho animal, a inclusão de palha de trevo vesiculoso na fração volumosa da dieta de bovinos é viável, tendo em vista que, mesmo no nível de substituição mais elevado, o GMD dos animais foi de um quilograma, o que demonstra o seu potencial de utilização na produção de bovinos.