Effects Of Different Organic Amendments Research Articles

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.

Management of pig manure to mitigate NO and yield-scaled N2O emissions in an irrigated Mediterranean crop

Substitution of conventional mineral fertilizers with organic sources can avoid the environmental problems associated with high concentrations of intensive livestock production in some Mediterranean areas. Some management practices, such as the use of nitrification inhibitors or more efficient irrigation techniques (e.g., drip irrigation), have been suggested as effective alternatives to mitigate nitrous oxide (N2O) and nitric oxide (NO) emissions released from soils amended with synthetic and organic fertilizers. In this experiment, we aimed to assess the effect of different organic amendments derived from pig manure (control without N fertilization (C); liquid fraction of pig slurry (LFPS); pig urine with the nitrification inhibitor 3,4 dimethylpyrazolephosphate (DMPP) (LFPSI); compost from the solid phase of pig slurry (COM)) compared to urea (U) and two different irrigation systems (the widespread sprinkler and alternative drip irrigation systems) on greenhouse gas (N2O, methane, CH4, and carbon dioxide, CO2) and NO emissions in a maize (Zea mays L.) crop. The effect of these treatments on crop yields and yield-scaled N2O emissions were also evaluated. The use of DMPP with LFPS was an effective practice to reduce N2O and NO losses (40 and 32% mitigation, respectively, compared to LFPS alone), and was also associated with the highest rates of CH4 oxidation. Drip irrigation significantly reduced the global warming potential (in spite of a lower CH4 sink) but increased the NO losses by 58%, as opposed to sprinkler irrigation. The higher biomass production and similar grain yields observed with drip irrigation resulted in lower yield-scaled N2O emissions in this treatment than in sprinkler irrigation. The use of organic fertilizers penalized grain yields compared to U (16–33%), although the differences were not significant in the case of LFPSI. Consequently, LFPSI in drip irrigation was (together with U applied by drip-fertigation) the treatment that led to the lowest yield-scaled N2O emissions. The use of organic N sources in irrigated maize is an environmentally advisable strategy in Mediterranean cropping systems, but an optimum balance between N oxides and greenhouse gas losses, N efficiency and crop yields requires the use of nitrification inhibitors (e.g., DMPP) with liquid organic sources.

Retention of Moisture in Soil With Organic Amendments Cultivated with Amaranthus Hypochondriacus

A field experiment was conducted to investigate the effect of different organic amendments (corn stubble and amaranth stubble, goat manure, compost, and green fertilizer (Medicago sativa)), alone and in combination with a hydrogel, into the moisture retention of the soil, deposited over the soil surface and mixed with surface soil, making a total of 14 treatments. To test their effects, the amaranth plants (Amaranthus hypochondriacus L.), were subjected to different periods of drought. Considered as tolerant to the drought and estimating their vegetative development for leaf production, the treatments were proven under random arrays with 10 repetitions. The agronomic variables considered were, height and survival of the plants as well as their stem diameter. The amendments do not present significant effects on the retention of moisture at 5 cm soil depth. In relation to the vegetative parameters, the hydrogel application demonstrates significant statistical differences for the survey of the plants (p>0.05). The amendments evaluated under the organic padding conditions with corn stubble, in conjunction with the green Medicago sativa fertilizer and the corn stubble mixed with soil, were the treatments which present the best results, in both stem diameter and plant height (Tukey`s test, α=0.05). All the variables show significant statistical differences according to the drought periods of between 0 and 15 days, applied to the different essays.

Effects of Different Organic Soil Amendments on Yield Parameters of Brassica rapa L. subsp. sylvestris

Brassica rapa L. subsp. sylvestris is one of the widely consumed vegetable in Puglia region of Italy. An experiment was conducted in experiment field of CHIEAM The Mediterranean Agronomic Institute of Bari (IAMB) to assess the effects of different organic amendments on yield parameters of turnip. Amendments used (a) coffee chaff compost, (b) coffee chaff (raw material), (c) control, (d) the commercial organic fertilizer. The rates of application were 6.3 tons ha-1 for coffee chaff compost, 7.5 tons ha-1 for coffee chaff and 9.3 tons ha-1 for the commercial organic fertilizer. The result indicated that the commercial organic fertilizer had highest values on number of leaves, plant height, fresh weight, dry weight and marketable yield (p<0.05) and there were no significant difference between other soil amendments. The commercial organic fertilizer was suitable in short term for turnip production when compared with compost and coffee chaff. It is recommended that Brassica rapa L. subsp. sylvestris can be grown successfully using the commercial organic fertilizer.

Evaluation of Organic Amendments Using Poultry Manure for the Improvement of Physical and Physico-chemical Properties of Theri Soil

To evaluate the effect of different Organic amendments including Poultry and their different proportions on various physico-chemical and physical properties on theri soil. Investigations were carried out on the surface (15 cm depth) of soil samples were collected from the village of Punnai Nagar (Kachanavillai) in Tuticorin district, Tiruchendur Taluk, Tamilnadu. The experiment s were carried out during 2014(Oct) to 2015(Jan) was laid out in Pot culture with 10 treatments and 3 replications. All the amendments were applied and wetting with water regularly for 90 days without allowing them to get dried. After 90 days measurements were made. The result revealed that the use of organic amendment will increases NPK, Water holding capacity, Pore space, EC, Organic Carbon and decreased pH, bulk density, Particle density, Hydraulic conductivity. These changes in soil environment improved the soil fertility without affecting soil health.

The impact of manure, straw and biochar amendments on aggregation and erosion in a hillslope Ultisol

Soil erosion is a serious problem in subtropical China where hillslope red soils (Ultisols in US soil taxonomy) are intensively cultivated. Manure and amendments have been reported to improve crop growth and soil structural stability in long-term experiments so the objective of this study was to determine the effect of different organic amendments on soil aggregate stability, agronomic performance, runoff, and erosion. Four treatments consisted of inorganic NPK fertilizer (NPK), NPK fertilizer plus rice straw mulch (NPK+Str), NPK fertilizer plus rice straw-derived biochar (NPK+BC), and NPK fertilizer plus swine manure (NPK+OM) located on land with a 9–14% slope planted with peanut (Arachis hypogaea L.). During the peanut season, soil erosion ranged from around 2600tonkm−2 with just inorganic NPK fertilizer down to 627tonkm−2 with fertilizer plus swine manure, while addition of swine manure also increased the above-ground biomass and SOC (P<0.05). In contrast, rice straw-derived biochar did not improve soil acidity, crop growth, and aggregation (P>0.05) except the SOC, because biochar was susceptible to erosion (2115tonkm−2). The least erosion was observed in the straw mulch treatment (225tonkm−2), while it improved the above-ground biomass (P<0.05) but not the C stock. The results indicated that the application of organic manure was a more appropriate practice for hillslope Ultisols management than using biochar.

Effect of different organic amendments on lettuce fusarium wilt and on selected soilborne microorganisms

This study evaluated the effect of different organic amendments on lettuce fusarium wilt caused by Fusarium oxysporum f. sp. lactucae in pots under controlled conditions. Their effects on the density of the pathogen, on the total fungi and on fluorescent Pseudomonas spp. were also evaluated after two subsequent lettuce crops. A significant reduction in the severity of the symptoms of F. oxysporum f. sp. lactucae was found after the use of Brassica carinata pellets (52–79% reduction) and compost (49–67% reduction), while Brassica green manure and cattle and chicken manure only provided partial control of fusarium wilt. However, variations in effectiveness were observed for the same treatment in repeated trials. In general, an increase was observed in Pseudomonas and a decrease in fungal populations in the growing medium, which was obtained by mixing a blonde sphagnum peat and a sandy loam soil with B. carinata pellets and compost after two consecutive cropping cycles. Prolonging the Brassica and compost treatments from 30 to 60 days did not significantly affect disease severity, plant growth or the microbial population of the total fungi or Pseudomonas. The largest lettuce biomass was obtained in the non‐inoculated growing medium amended with brassica flour, chicken manure, B. carinata pellets and compost, as a consequence of fertilization. The treatment with B. juncea green manure, B. carinata (pellets and flour) and compost applied 30 days before planting led to promising results and merits further investigation for use under field conditions.

Short-Term Effects of Different Organic Amendments on Soil Properties and Organic Broccoli Growth and Yield

ABSTRACTThe aim of this study was to evaluate the effects of different organic fertility sources on organic broccoli (Brassica oleracea var. italica) growth and yield, and on soil properties. The fertilization was designed to supply the crop with about 100 kg ha−1 of N using two amendments: a municipal solid wastes-based compost (CC), and a manure based compost (CB). The former was used alone (T1), in combination with its own water extract (CT) in fertigation (T2), and in combination to CT applied in fertigation and as foliar spray (T3). Other treatments resulted from the application of (i) CC and CB (T4); (ii) CB alone (T5); and (iii) the exhausted compost (EX) resulting from the extraction of CT (T6). Unamended plots were used as control (T7). Selected soil properties were determined at the beginning and at the end of the trial in order to estimate the effects of the various treatments on these parameters. The best yields were obtained with T4 and T5 (16.95 and 18.46 t ha−1, respectively). The application of CC alone (T1) showed slightly better growing parameters in comparison to its application in combination to CT (T2 and T3), even though the yields were not significantly different from each other. T6 showed the lowest yield of broccoli (7.03 t ha−1) among the treatments, superior only to the unfertilized control (5.38 t ha−1, T7). The different fertilizations showed a general soil enrichment of available phosphorous and organic matter, even if the latter could be only transitory. Finally, the high production costs and the low yields obtained apparently dissuade the use of compost tea and exhausted compost for the fertilization of broccoli crop.

Nutrient Analysis, Decomposition, and Nitrogen Mineralization of Various Organic Amendments Used for Pechay Production

Farmers are increasingly using alternative fertilizer inputs such as manures and composts due to the high cost of inorganic fertilizers. However, different organic amendments have varied characteristics and thus also their effects on soil properties and the growth and yield of crops. The study was conducted to determine the characteristics and nutrient content of organic amendments, evaluate the decomposition rate and nitrogen mineralization rate of the various organic amendments, and examine the effects of different organic amendments on pechay. Four organic amendments used include swine manure, chicken dung, mudpress, and vermicast. These were analyzed for total elemental analysis, microbial decomposition, and nitrogen mineralization rate. A pot experiment was carried out to test the effects of these amendments on the growth and yield of pechay. Results showed that organic amended soil significantly increased the rates of microbial decomposition and nitrogen mineralization, organic material content, and the growth and yield of pechay. In terms of total elemental analysis, chicken dung had the highest content of essential nutrients such as P, K, Ca, and Cl as compared to mudpress, vermicast, swine manure, hence, has good potential as source of organic fertilizer for vegetable production. High amounts of heavy metals such as lead, strontium, nickel, copper, and zinc were detected in the swine manure.

Effect of different organic amendments on the dissipation of linuron, diazinon and myclobutanil in an agricultural soil incubated for different time periods

Dissipation kinetics of pesticides belonging to three chemical groups (linuron, diazinon and myclobutanil) was studied in an unamended agricultural soil and in this soil amended with three organic residues: sewage sludge (SS), grape marc (GM) and spent mushroom substrate (SMS). The soils were incubated with the residues outdoors for one and 12months. Mineralized, extracted and non-extractable fractions were also studied for 14C-linuron and 14C-diazinon. The dissipation kinetics was fitted to single first-order or first-order multicompartment models. The dissipation rate (k) decreased in the order diazinon>linuron>myclobutanil, and DT50 values decreased for linuron (1.6–4.8 times) or increased for myclobutanil (1.7–2.6 times) and diazinon (1.8–2.3 times) in the amended soils relative to the unamended soil. The lowest DT50 values for the three pesticides were recorded in GM-amended soil, and the highest values in SMS-amended soil. After 12months of soil incubation, DT50 values decreased in both the unamended and amended soils for linuron, but increased for the unamended and SMS-amended soil for diazinon and myclobutanil. A certain relationship was observed between the sorption of pesticides by the soils and DT50 values, although it was significant only for myclobutanil (p<0.05). Dissipation mechanism recorded the lowest mineralization of 14C-pesticides in the GM-soil despite the highest dissipation rate in this soil. The extracted 14C-residues decreased with incubation time, with increased formation of non-extractable residues, higher in amended soils relative to the unamended soil. Soil dehydrogenase activity was, in general, stimulated by the addition of the organic amendments and pesticides to the soil after one month and 12months of incubation. The results obtained revealed that the simultaneous use of amendments and pesticides in soils requires a previous study in order to check the environmental specific persistence of these compounds and their effectiveness in amended soils.

Effects of organic amendments with various nitrogen levels on arbuscular mycorrhizal fungal growth

Arbuscular mycorrhizal fungi (AMF) are plant symbionts capable of enhancing nutrient uptake and improving soil structure. These features have brought AMF into focus as a component of soil restoration practices in ecosystems with degraded or highly eroded soils. It has been suggested that increasing the levels of organic material in the soil will enhance the production of AMF biomass, and that organic amendments with high concentrations of nitrogen (N) generate the largest increases in AMF growth. We tested the effects of different organic amendments and N sources on AMF responses in a natural sand dune system and pot cultures of Zea Mays L. The in-growth of AMF was measured as relative biomass through analyses of signature phospholipid fatty acids (PLFA) and neutral lipid fatty acids (NLFA) from mesh bags with different treatments. In the field, results showed a significant positive effect in AMF growth from adding a naturally N-rich organic amendment (alfalfa).Amendments of the low-N organic amendment (barley straw) produced no positive effect, and the effect was negative when ammonium nitrate (NH4NO3) was added to the barley straw to simulate the N concentrations of alfalfa. Saprophytic fungi, on the other hand, were stimulated by additions of NH4NO3. In greenhouse conditions, alfalfa and yeast extract were found to have a similar effect on AMF growth when added proportionally to their N content, even though their mass and texture are distinct. These results suggest the N content in organic amendments does play a role in its effect on AMF growth. There are also indications that the organic or inorganic nature of the N could determine its effect on AMF growth, possibly through interactions with the surrounding microbial community. This aspect requires further investigation.

Effects of Organic Amendments on Productivity and Profitability of Bell Pepper–French Bean–Garden Pea System and on Soil Properties during Transition to Organic Production

A transition period of at least 2 years is required for annual crops before the produce may be certified as organically grown. There is a need to better understand the various management options for a smooth transition from conventional to organic production. The purpose of this study was to evaluate the effects of different organic amendments and biofertilizers (BFs) on productivity and profitability of a bell pepper–french bean–garden pea system as well as soil fertility and enzymatic activities during conversion to organic production. For this, the following six treatments were established in fixed plots: composted farmyard manure (FYMC, T1); vermicompost (VC, T2); poultry manure (PM, T3) along with biofertilizers (BF) [Rhizobium/Azotobacter + phosphorus solubilizing bacteria (Pseudomonas striata)]; mix of three amendments (FYMC + PM + VC + BF, T4); integrated nutrient management (FYMC + NPK, T5); and unamended control (T6). The yields of bell pepper and french bean under organic nutrient management were markedly lower (25.2–45.9% and 29.5–46.2%, respectively) than with the integrated nutrient management (INM). Among the organic treatments, T4 and T1 produced greater yields of both bell pepper (27.96 Mg ha−1) and french bean (3.87 Mg ha−1) compared with other treatments. In garden pea, however, T4 gave the greatest pod yield (7.27 Mg ha−1) and was significantly superior to other treatments except T5 and T1. The latter treatment resulted in the lowest soil bulk density (1.19 Mg m−3) compared with other treatments. Similarly, soil organic C was significantly greater in all the treatments (1.21–1.30%) except T2 compared to T6 (1.06%). Plots under INM, however, had greater levels of available nitrogen–phosphorus–potassium (NPK) than those under organic amendments. T1 plots showed greater dehydrogenase and acid phosphatase activities compared with other treatments. However, T4 and T5 plots had greater activities of β-glucosidase and urease activities, respectively. The cost of cultivation was greater under organic nutrient management (except T2) compared with INM. The latter treatment gave greater gross margin and benefit/cost (B/C) ratio for all vegetables, except that T2 gave greater B/C ratio in garden pea compared with other treatments. We conclude that T1 and T4 were more suitable for enhancing the productivity of bell pepper–french bean–garden pea system, through improved soil properties, during transition to organic production.

ORGANIC MATTER AMENDMENTS TO A SILT LOAM AND A LOAM SOIL ON 'O'NEAL' BLUEBERRY ORCHARDS IN SOUTH URUGUAY

Highbush blueberry (Vaccinium corymbosum L. hybrids) growth is limited in South Uruguay since soils do not meet their requirements of: good drainage, low pH, and without compaction. The addition of organic matter to the soil could overcome some of these limitations. The objective of this study was to determine the effect of different organic amendments on some soil physical and chemical properties, and Higbush blueberry 'O'Neal' growth. Two trials arranged in a randomized complete block design with three replications were conducted, one in a fine silty Typic Argiudoll (trial 1), and the other one in a fine loamy Typic Argiudoll (trial 2). In trial 1, treatments were rice hull, eucalyptus sawdust and rice hull mixture, eucalyptus sawdust, and pine sawdust and pine bark mixture, at rates of 31, 36, 41, and 45 mg.ha -1 of dry matter, respectively. In trial 2, treatments were, rice hull, eucalyptus sawdust, Lithuanian peat, eucalyptus and pine sawdust mixture, and pine sawdust and pine bark mixture; at rates of 47, 61, 65, 67 and 70 mg.ha -1 of dry matter, respectively. A control without amendment was included in both trials. All amendments increased soil organic carbon and particulate organic matter as compared to the non-amended control. After 10 months of amendments application there were no differences among treatments. In trial 1, bulk density was lowered by rice hull alone or mixed with eucalyptus sawdust for the first ten months. Lithuanian peat resulted in lower pH values for the first six months, afterwards the effect dissapeared. Contrary to the excpected, pine sawdust had any acidification effect. In trial 2, all amendments improved shoot length respect to the control. Root volume exploration was almost doubled by the sawdusts mixture at 67 mg.ha -1 one year after being transplanted. Eucalyptus sawdust had no allelopathic effect, being promising for use as amendment for cultivating blueberries on mineral soils.

Influence of Different Organic Amendments on the Leaching and Dissipation of Terbuthylazine in a Column and a Field Study

Terbuthylazine (TA) is a herbicide that has been introduced for weed control in corn cultivations as a direct replacement for atrazine. Because incorporation of different organic amendments (OAs) is a common practice in this crop, this study investigated the effects of different OAs, including urban sewage sludge, poultry compost, and corn straw on the dissipation and metabolism of TA. A column study and a field dissipation study were used. In the column study, no residues of TA and desethyl-terbuthylazine (DETA) were detected in the leachate of amended and non-amended columns. The addition of OAs increased the persistence of TA and DETA in the upper soil layers (0-10 cm) but did not affect the mobility of TA and DETA in either experiment. Although the presence of OAs led to a significant increase in DETA production in the upper soil layers, the presence of DETA in lower depths did not significantly differ with the non-amended soil in either experiment. A gradual accumulation of DETA was evident in the soil layers amended with corn straw, whereas a rapid formation of DETA and a gradual decline thereafter was observed in the other treatments. Overall, the addition of OAs did not appear to significantly influence the mobility of TA and DETA, which did not move below the top 30 cm, thus indicating low risk for ground water contamination. In addition, the dissipation rate of TA in the field was faster than that in the column study.

Effect of different organic amendments on the resistance and resilience of the organic matter decomposing ability of soil and the role of aggregated soil structure

The effect of organic amendment on the resistance and resilience of the organic matter decomposing activity was compared between soils amended with compost and with chemical fertilizers. The impact of metam sodium disinfection on cellulose-decomposing activity and on the number of nematodes in three types of soils was periodically measured. In an andosol, cellulose-decomposing activity was significantly suppressed by soil disinfection only in the chemically fertilized soil (CF-soil) and not in the soils to which cow manure compost and okara (the residue in tofu production)/coffee compost was added. In a brown lowland soil, cellulose-decomposing activity was significantly suppressed by soil disinfection in the CF-soil, but not in the soils to which higher amounts of cow manure compost and pig manure compost had been added. In a red-yellow soil, cellulose-decomposing activity was significantly suppressed by soil disinfection in all soils, but its resilience was higher in the soils to which cow manure compost or coffee compost was added compared with the CF-soil. Total numbers of nematodes were markedly decreased by soil disinfection in all soils. These results may suggest that the resistance and resilience of cellulose-decomposing activity against soil disinfection were enhanced by organic amendments, while disinfection had fatal effects on soil nematodes. In most of the organically amended soils, the mean weight diameters of aggregates were larger compared with the CF-soils, suggesting that highly structured soil pore networks may provide shelters for the soil microbes responsible for cellulose decomposition against disinfection. This hypothesis was supported by the result that the resistance of cellulose-decomposing activity against soil disinfection decreased when the soil structure was destroyed by grinding in a mortal and pestle.

Cultivation of high-biomass crops on coal mine spoil banks: Can microbial inoculation compensate for high doses of organic matter?

Two greenhouse experiments were focused on the application of arbuscular mycorrhizal fungi (AMF) and plant growth promoting rhizobacteria (PGPR) in planting of high-biomass crops on reclaimed spoil banks. In the first experiment, we tested the effects of different organic amendments on growth of alfalfa and on the introduced microorganisms. While growth of plants was supported in substrate with compost amendment, mycorrhizal colonization was suppressed. Lignocellulose papermill waste had no negative effects on AMF, but did not positively affect growth of plants. The mixture of these two amendments was found to be optimal in both respects, plant growth and mycorrhizal development. Decreasing doses of this mixture amendment were used in the second experiment, where the effects of microbial inoculation (assumed to compensate for reduced doses of organic matter) on growth of two high-biomass crops, hemp and reed canarygrass, were studied. Plant growth response to microbial inoculation was either positive or negative, depending on the dose of the applied amendment and plant species.

Effects of different organic amendments on the structure of an ultisol in Rivers State, Nigeria

Organic materials have been shown to improve soil physical and chemical properties. A 12 weeks field experiment was used to assess the effects of amending soil with organic materials [poultry droppings (PD), maize straw (MS), cassava peelings (CP) and ripe plantain peelings (RPP)] on soil bulk density (BD), total porosity (P), saturated hydraulic conductivity (Ks) and soil moisture retention (SMR). Results showed that Ks, BD, P and SMR were significantly positively affected by all the treatments. At the end of 12 weeks, Ks increased by 508, 386, 344, and 172 percents for RPP, PD, MS and CP respectively. Bulk density dropped from 2.14 to 1.97, 1.98, 2.03, 2.07 Kgm-3 for RPP, PD, MS and CP respectively. The same trend was observed for porosity. For all parameters measured, RPP better improved structure than the other organic materials; from the 6th week. The faster decomposition of this material, relative to the others, may have contributed to this. International Journal of Agriculture and Rural Development Vol. 7(1) 2006: 61-66

Effects of different organic amendments on seed germination and soil physical properties

A screen house study was carried out to assess the effects of three organic amendments (poultry droppings – pd, brewer's spent grain – bsg and wood shavings-ws) on the germination of four crops (Maize: Zea mays , Cowpea: Vigna sinensis , Okro: Abelmoschus esculentum and pepper: Capsicum annum ), and on some properties; of an ultisol in Port – Harcourt, southeastern Nigeria. The four treatments, made up of the organic amendments were laid out in a completely randomized design replicated thrice, for each of the crops. Wood shavings were best suited for pepper and maize with 77.7 and 43.3 percents germination, respectively as against their controls of 59.9 and 33.3 percents. Brewer's spent grain gave a germination rate of 60% for cowpea while the poultry droppings treatment gave 100% germination for okra. Generally, the wood shavings enhanced germination for all the crops. Organic amendments reduced bulk density by 8.2,4.5 and 38.1% and increased porosity by 10.2, 6.1 and 40% for poultry droppings brewer's spent grain and wood shavings respectively. Wood shavings and poultry droppings significantly increased volumetric moisture contents from 0.37 to 0.50 and 0.43 respectively. There were inverse linear relationships between percentage germination and volumetric moisture contents for all treatments, with r-values of -0.06, -0.54, and -046 for PD, BSG and WS respectively. There were also the same relationship between percentage germination and bulk density for only PD and WS respectively. There were also the same relationship between percentage germination and bulk density for only PD and WS with r-values of -0.31 and -0.83 respectively. International Journal of Agriculture and Rural Development Vol. 7(2) 2006: 134-140

Effect of organic amendments on Verticillium wilt of cotton

Verticillium wilt is the most devastating disease of cotton in China and a challenge for producers to find effective means of control. Here, we report the effects of different organic amendments on the incidence of this disease and on the rhizosphere microflora of cotton plants. Seven organic amendments were evaluated for their suppressive effect on cotton Verticillium wilt caused by Verticillium dahliae Kleb. The results showed that organic amendments applied to soil reduced disease severity in both inoculated pots and naturally infested cotton field plots. The most effective control was achieved with crab shell (chitin), soybean stalk and alfalfa, and in pots the efficacy was 72%, 60% and 56% for vascular tissues, respectively. Rice chaff gave moderate control, while poultry manure, peanut cake and wheat straw showed a weak suppressive effect with efficacy of 21%, 28% and 11% for vascular tissues, respectively. Organic amendments increased the population size of rhizosphere microbes (including fungi, bacteria and actinomycetes), which varied at the different ages of the cotton plants. The organic materials with the best biocontrol capacity strongly stimulated the proliferation of antagonists to V. dahliae in the rhizosphere. However, poultry manure, peanut cake and wheat straw caused only small changes in the total numbers of microflora and the percentage of antagonists was lower. Extracts from organic amendments were highly inhibitory to V. dahliae. The changes undergone by rhizosphere microbes after the addition of organic amendments may contribute to suppression of cotton wilt and help to explain the protective effect of the amendments. The results indicate that application of organic amendments is an effective control measure against cotton Verticillium wilt.

Manioc peel and charcoal: a potential organic amendment for sustainable soil fertility in the tropics

In tropical areas, where crop production is limited by low soil quality, the development of techniques improving soil fertility without damage to the environment is a priority. In French Guiana, we used subsistence farmer plots on poor acidic soils to test the effect of different organic amendments, bitter manioc peel (M), sawdust (Sw) and charcoal (Ch), on soil nutrient content, earthworm abundance and yard-long bean (Vigna unguiculata sesquipedalis) production. The peregrine Pontoscolex corethrurus was the only earthworm species found. Pod production and plant growth were lowest in unamended soil. The application of a mixture of manioc peel and charcoal (M + Ch) improved legume production compared with other organic mixtures. It combined the favourable effects of manioc peel and charcoal. Manioc peel improved soil fertility through its low C:N ratio and its high P content, while charcoal decreased soil acidity and exchangeable Al and increased Ca and Mg availability, thus alleviating the possible toxic effects of Al on plant growth. The M + Ch treatment was favourable to P. corethrurus, the juvenile population of which reached a size comparable to that of the nearby uncultivated soil. The application of a mixture of manioc peel and charcoal, by improving crop production and soil fertility and enhancing earthworm activity, could be a potentially efficient organic manure for legume production in tropical areas where manioc is cultivated under slash-and-burn shifting agriculture.