Competition for Nitrogen Between Thorn Apple and Tomato and Pepper

The effect of emergence time of the weed Datura stramonium (thorn apple) on tomato (Lycopersicon esculentum Mill.) and pepper (Capsicum annuum L.) was evaluated in a greenhouse experiment. The closer emergence of the weed was to that of the crops, the greater was the weed's growth, seed production, and nitrogen (N) uptake. As a result, growth, fruit yield, and N uptake of the crops was reduced. Shoot N content was reduced in tomato, as was fruit N content in pepper. There was competition by the weed with the crops for N, even when weed emergence was as late as the beginning of flowering. This competition, and the damage it caused, was always more severe with respect to pepper than tomato, irrespective of weed emergence time. The earlier the emergence of Datura stramonium, the fewer were the number of fruits produced by either crop. Average fresh fruit weight in tomato was also reduced. In pepper, the average fruit weight was reduced only when the weed emerged up to the four-leaf stage of the crop. The drop in pepper fruit yield caused by weed emergence up to the four-leaf stage of the crop could be due to competition for light by the weed, in addition to competition for N. Tomato competed better against the weed than did pepper.     

Boron Toxicity Alters Nitrate Reductase Activity,Proline Accumulation,Membrane Permeability,and Mineral Constituents of Tomato and Pepper Plants

ABSTRACT

Boron (B) toxicity is an important disorder that can limit plant growth on soils of arid and semi arid environments throughout the world. Although of considerable agronomic importance, our understanding of B toxicity is rather fragmented and limited. The effects of increasing levels of B (0, 0.5, 5, 50 mg kg^{? 1}) on plant growth, proline accumulation, membrane permeability, nitrate reductase activity (NRA), and mineral nutrient interactions of tomato and pepper plants were investigated in greenhouse conditions. Increasing levels of B increased the B contents of plants. Boron toxicity symptoms occurred at 5 and 50 mg kg^{? 1} levels. Fresh and dry weights of the plants clearly decreased with the application of the 50 mg kg^{? 1} level of B. Membrane permeability and proline accumulation were significantly increased by the 50 mg kg^{? 1} level of B. Nitrate reductase activity of tomato plants was increased with increasing levels of B. With the exception of potassium (K) and calcium (Ca) in pepper and magnesium (Mg) in tomato, B treatments significantly affected nutrient concentrations of tomato and pepper. Except for sulfur (S) and Ca in tomato, the highest rate of B applied increased the N, phosphorus (P), and K concentrations of tomato and N, P, Mg, and S concentrations of pepper.     

A comparision of the competitive effects and nutrient accumulation of fat‐hen and groundsel

The competitive effects of fat‐hen (chenopodium album L.) and groundsel (Senecio vulgaris L.) on tomato (Lycopersicon esculentum Mill), lettuce (Lactuca sativa L.) and cabbage (Brassica oleracea L. var. Capitata) were investigated under glasshouse conditions. Weed competition severely reduced growth of the three food crops, the reduction being more pronounced with the longer exposure to the competition. Chenopodium album and 5. vulgaris were considerably different in their competitive abilities, although similar differences among the three food‐crop species were found. Senecio vulgaris was affected more by the competition than C. album and had lower tissue concentrations of N, K, and Mg. Growth of both weeds was greatly suppressed when tomato emerged two weeks earlier than the weeds, but the crop plants were severely stunted when the weeds had two weeks initial advantage. It appeared that C. album competed with the three food crops more for K than other elements, while S. vulgaris competed better for P. Cabbage was more competitive with both weed species than tomato while lettuce was the least competitor. Some aspects of these differences in competitive ability among the species could be related to their nutrient use.     

生物有机肥对田间蔬菜根际土壤中病原菌和功能菌组成的影响

利用实时荧光定量PCR方法对田间条件下连作番茄和辣椒施用生物有机肥(BOF)和常规施肥(CK)的根际土壤微生物中青枯病原菌和功能菌群(固氮菌和荧光假单胞菌)的数量进行定量研究.结果表明:与CK相比,BOF处理的番茄和辣椒产量分别提高了26.0％和19.9％,青枯病发病率分别降低了41.5％和44.7％,番茄和辣椒植株根际土壤固氮菌数量分别增加了23.5％和25.8％、荧光假单胞菌数量分别增加了29.5％和20.2％、病原菌数量分别减少了73.2％和90.1％.生物有机肥能够调控根际微生物区系的组成,降低土传病害的发病率,促进作物健康生长;实时荧光定量PCR方法能够快速准确地检测根际土壤中功能微生物种群数量变化.     

Effects of repeated clover undersowing,green manure ley and weed harrowing on weeds and yields in organic cereals

Abstract

Cover crops can be used to reduce leaching and erosion, introduce variability into crop rotation and fix nitrogen (N) for use by the main crops, less is however known about effects on weeds. The effects on weed seed bank, weed growth and grain yield of 4 years of annual undersown clover and ryegrass alone and in combination, and one of the 4 years with clover or clover + grass as green manure, were studied in oat and spring wheat at two experimental sites in south-eastern Norway. These treatments were compared with no undersown crop (control) and with weed harrowing. In contrast to many results in the literature, the undersown clover in this study did not suppress annual weeds, but fertilized the weeds as well as the cereals. Undersown clover resulted in a statistically significant increase of grain yield at the two sites to 116% and 121% of control. During the 4-year period relative seed bank and density of emerged weed (dominated by Spergula arvensis) increased significantly about 4.5 and 10 times respectively in the undersown clover plots at Apelsvoll. At Kise both ryegrass alone and ryegrass mixed with clover significantly suppressed the weed biomass to 70% and 74% of control respectively. It is concluded that fertilization effects of undersown clover may have dominated and overriden the competitive effects. One whole-season clover green manure did not increase the mean yield, but resulted in a significant drop in seed bank size the following year, because of limited weed establishment in an established ley. Only a slight increase in average weed biomass was observed at one of the two experimental sites. The weed seed bank and the weed biomass were essentially kept at steady state during the experimental period in harrowed plots, but harrowing decreased grain yield significantly at both sites.     

Cover crop potential of winter oilseed crops in the Northern U.S. Corn Belt

ABSTRACT

Winter camelina [WC, Camelina sativa (L.) Crantz] and field pennycress (FP, Thlaspi arvense L.) are emerging oilseed crops in corn–soybean rotations, but little is known about their cover crop potential. A 2-year study was conducted in Minnesota, USA to evaluate the effect of winter oilseed crops on nitrogen (N) use, growth and yield of corn and soybean. Treatments included WC, FP, winter rye (WR, Secale cereale L.), and a no cover crop (NC) control. Oilseed crops produced 40–50% less spring biomass and accumulated less N compared to WR. The tissue-N of WC and FP was 39.0% and 6.6% higher than WR, respectively. The C:N ratio of cover crops was lower than 20:1, suggesting rapid decomposition. Compared with NC, cover crops lowered soil nitrate before major crops planting, but the post-harvest N profile following corn and soybean was not affected. Compared with NC, cover crops significantly decreased corn yield, with 8.7%, 9.5% and 9.8% reduction following WC, FP and WR, respectively. Cover crops did not affect growth, yield and N uptake of soybean. Oilseed crops showed potential to improve N cycling in the rotation, but more research of their impact on major crops is needed.     

Growth and nutrient interrelationships of three vegetable crops with different sensitivities to soil pH as affected by lime and fertilizer treatments

Abstract

In seeking reasons for differences in sensitivity among vegetables to low soil pH and the roles of lime and fertilizers, an experiment was conducted in 1984 with 3 crops: snapbeans (Phaseolus vulgaris L.), tomatoes (Lycopersicon esculentum L.), and red beets (Beta vulgaris L.). The lime treatments, check, calcitic lime, and dolomitic lime, were applied in 1979 and resulted in soil pH levels of 5.5, 6.9 and 6.7, respectively, at the time of planting. Banded fertilizer treatments were randomized in each lime plot. These were: check, NP, N, NPK, NPCa, and NPMg for snapbeans while with tomatoes and beets, K was added to the N, NPCa and NPMg treatments. Leaf samples from each plot were analyzed for 11 elements.

Growth responses of the 3 crops were related to the plant sensitivity to acid soils. When grown on soil with pH 5.5, snapbean vine weights and pod yields were not affected, tomato yields tended to be lower, and red beet yields were substantially reduced. Leaf Mn levels increased with the greater sensitivity to acid soils. Both calcitic and dolomitic limes had little effect on snapbean yields, moderate effects on tomato yields, and more than doubled yields of red beets. Lime types affected primarily leaf Ca and Mg. The NPK fertilizer treatment increased yields of tomatoes and red beets but increased only vine weights of snapbeans. Leaf Mn was increased substantially in the NPK treatment. When gypsum or Epsom salts was added, yields were not affected.

The sensitivity of red beets and to a lesser extent tomatoes could not be explained on the basis of manganese toxicity or poor uptake of calcium or magnesium. The results did suggest that poor phosphorus uptake could be a primary cause.     

An investigation of the impact of Glomus clarum (mycorrhiza) on the growth of tomato (Lycopersicum esculentum mill.) on both sterilized and non-sterilized soils

Abstract

A greenhouse experiment was carried out to investigate the influence of Glomus clarum (mycorrhiza) on the growth of tomato seedlings grown in both sterilized and non-sterilized soils. Highest growth parameter values were recorded in tomato plants inoculated with mycorrhiza but grown in sterilized soil, followed by those grown in non-sterilized soil but inoculated with mycorrhiza also. Sterilized but non-inoculated tomato plants also had growth and were closely followed by non-sterilized, non-inoculated tomato plants. There was no significant difference in all the treatments when girth of the tomato plants used was measured in this study. Nutrient uptake (N,P,K) was significantly found highest in the inoculated sterilized tomato plants while it was found lowest in the non-sterilized, non-inoculated tomato plants. Generally, mycorrhizal-inoculated tomato plants (whether sterilized or non-sterilized) showed better growth in all the treatments used.     

Role of Cover Crops and Planting Dates for Improved Weed Suppression and Nitrogen Recovery in No till Systems

ABSTRACT

Cover crops improve the recovery and recycling of nitrogen and impart weed suppression in crop production. A two-year study with six weekly plantings of cover crops including non-winterkilled species (hairy vetch, Vicia villosa L.; winter rye Secale cereale L.) and winterkilled species (oat, Avena sativa L.; forage radish, Raphanus sativus L.) were assessed for effects on growth of forage rape (Brassica napus L.) and weed suppression. Early planting of cover crops gave the highest biomass and highest nitrogen accumulation. Delaying planting from early-September to mid-October suppressed cover-crop biomass by about 40%. Forage radish produced more biomass in the fall than other cover crops but was winter killed. Spring biomass was highest with rye or vetch. All cover crops suppressed weeds, but suppression was greatest under rye or hairy vetch. Hairy vetch accumulated the largest nitrogen content. Forage rape plants yielded more biomass after a cover crop than after no-cover crop.     

Response of bell pepper grown inside plastic houses to nitrogen fertigation

Abstract

Two field experiments were conducted for two consecutive seasons inside plastic houses to evaluate bell pepper (Capsicum annuum) response to nitrogen fertigation. Nitrogen fertilizers were applied through irrigation water at rates of zero, 150, 250, and 350 N kg ha^‐1. The crops were irrigated in weekly bases with the amount of water equivalent to 80% of the E Pan reading. All treatments were replicated four times in a randomized complete block design. Five plants were sampled from each experimental unit at 30, 60, 90, 120, 150, and 180 days after planting. Growth rate, nutrient uptake and yield were determined. The results indicate that the yield and marketable number of fruits in both seasons increased with the addition of nitrogen. The highest yield was obtained with the addition of 150 kg N ha^‐1. The maximum growth rate and the maximum rate of accumulation of dry matter in the fruits occurred during the period of 90 to 150 days after planting. This may indicate that the peak of the pepper N requirement and utilization would be during the same period of the maximum growth rate. Increasing the rates of nitrogen applied increased the uptake of nitrogen by the plants and at the same time stimulated the uptake of potassium and phosphorus through the synergistic effect of nitrogen on both nutrients.     

Stenotrophomonas rhizophila DSM14405T promotes plant growth probably by altering fungal communities in the rhizosphere

Stenotrophomonas rhizophila DSM14405^T is of high biotechnological interest as plant growth stimulator, especially for salinated conditions. The objective of this study was to determine the effect of plant species (cotton, tomato, and sweet pepper) on colonisation and plant growth promotion of this beneficial bacterium in gnotobiotic systems and in non-sterile soil. All plant structures (leaves, stems, and roots) were densely colonised by DSM14405^T reaching up to 10⁹ cells g^?1 fresh weight; under gnotobiotic conditions the abundances were 4–5 orders of magnitude higher than in non-sterile soil. Under non-sterile conditions and ambient humidity, tomato shoots were more densely colonised than shoots of sweet pepper and cotton. S. rhizophila DSM14405^T was shown to grow endophytically and colonise the vicinity of root hairs of tomato. Plant growth promotion was particularly apparent in tomato. In general, the impact of plant species on colonisation and plant growth promotion was more pronounced in soil than under gnotobiotic conditions and likely due to the control of diseases and deleterious microorganisms. S. rhizophila DSM14405^T was shown to control diseases in sweet pepper and in cotton. Molecular profiling via single strand conformation polymorphism of internal transcribed spacers and 16S rRNA genes (PCR-single strand conformational polymorphism (SSCP)) revealed that S. rhizophila DSM14405^T strongly affected fungal, but not bacterial communities in the rhizosphere of tomato and sweet pepper. Major SSCP bands related to uncultured fungi and Candida subhashii, disappeared in tomato rhizosphere after Stenotrophomonas treatment. This suggests an indirect, species-specific plant growth promotion effect of S. rhizophila via the elimination of deleterious rhizosphere organisms.     

Changes of Soil Microbial Biomass Carbon and Nitrogen with Cover Crops and Irrigation in a Tomato Field

ABSTRACT

In order to understand how soil microbial biomass was influenced by incorporated residues of summer cover crops and by water regimes, soil microbial biomass carbon (C) and nitrogen (N) were investigated in tomato field plots in which three leguminous and a non-leguminous cover crop had been grown and incorporated into the soil. The cover crops were sunn hemp (Crotalaria juncea L., cv ‘Tropic Sun’), cowpea (Vigna unguiculata L. Walp, cv ‘Iron clay’), velvetbean (Mucuna deeringiana (Bort) Merr.), and sorghum sudangrass (Sorghum bicolor × S. bicolor var. sudanense (Piper) Stapf) vs. a fallow (bare soil). The tomato crop was irrigated at four different rates, i.e., irrigation initiated only when the water tension had reached ?5, ?10, ?20, or ?30 kPa, respectively. The results showed that sorghum sudangrass, cowpea, sunn hemp, and velvetbean increased microbial biomass C by 68.9%, 89.8%, 116.8%, and 137.7%, and microbial N by 58.3%, 100.0%, 297.3%, and 261.3%, respectively. A legume cover crop, cowpea, had no statistically significant greater effect on soil microbial C and N than the non-legume cover crop, sorghum sudangrass. The tropical legumes, velvetbean and sunn hemp, increased the microbial biomass N markedly. However, the various irrigation rates did not cause significant changes in either microbial N or microbial C. Soil microbial biomass was strongly related to the N concentration and/or the inverse of the C:N ratio of the cover crops and in the soil. Tomato plant biomass and tomato fruit yields correlated well with the level of soil microbial N and inversely with the soil C:N ratio. These results suggest that cover crops increase soil microbiological biomass through the decomposition of organic C. Legumes are more effective than non-legumes, because they contain larger quantities of N and lower C:N ratios than non-legumes.     

On‐farm monitoring of soil and crop nitrogen status by nitrate‐selective electrode

Abstract

Nitrate‐nitrogen concentration in fresh petiole sap, as measured by a portable, battery‐operated, nitrate‐selective electrode, was highly correlated with NO₃‐N concentration in dry petiole tissue of broccoli [Brassica oleracea L. (Italica group), r² = 0.84], celery [Apium graveolens L. var. dulce (Mill.) Pers., r² = 0.88], lettuce (Lacluca saliva L., r² = 0.77), pepper (Capsicum annuum var. annuum L., r² = 0.89), tomato (Lycopersicon esculentum Mill., r² = 0.83), and watermelon [Citrulius lanatus (Thunb.) Matsum. & Nakai, r² = 0.88]. This relationship was linear over a wide range of NO₃‐N values and was generally unaffected by site, crop, cultivar, or growth stage, provided that petiole tissue analyzed was from recently matured leaves. Sap was analyzed directly without dilution or filtration. The slope of the regression equation differed widely among crops. Selective electrode analysis of NO₃‐N concentration of soil solution samples obtained by suction lysimetry was also highly correlated with conventional laboratory technique (r² = 0.87). The nitrate‐selective electrode appeared to be a useful tool for on‐farm monitoring of soil and crop N status.     

The better suppression of pepper Phytophthora blight by arbuscular mycorrhizal (AM) fungus than Purpureocillium lilacinum alone or combined with AM fungus

Purpose

Phytophthora blight caused by Phytophthora capsici (Pc) is one of the most economically destructive soilborne diseases of pepper (Capsicum annum L.) on a global scale. Biocontrol using antagonistic microbes, such as Purpureocillium lilacinum (Pl) and arbuscular mycorrhizal (AM) fungus Funneliformis caledonium (Fc), is one of the significant strategies for ecologically sound plant disease management. The purpose of this work was to investigate the sole and combined suppression of pepper Phytophthora blight by Fc and Pl.

Materials and methods

The 14-week pot experiment with three pepper plants per pot included five treatments: control (non-inoculation), inoculation with Pc, inoculation with Pc and Pl (Pc?+?Pl), inoculation with Pc and Fc (Pc?+?Fc), and inoculation with Pc, Pl, and Fc (Pc?+?Pl?+?Fc). Pots were randomly arranged with eight replicates per treatment. The incidence and severity of Phytophthora blight at plant full productive stage were recorded. The biomasses and N, P, and K concentrations of pepper shoots, roots, and fruits were all measured. In addition, root mycorrhizal colonization rate and soil pH, phosphatase activity, and available P concentration were also tested.

Results and discussion

The inoculation of Pc induced both high incidence (92%) and severity (33%) of pepper Phytophthora blight, and the alleviating effects of Pl, Fc, and Pl?+?Fc were 46%, 79%, and 59%, respectively. The Fc significantly increased (P?<?0.05) root mycorrhizal colonization, nutrient (N, P, and K) acquisition, plant biomass, and fruit yield of pepper, while Pl only significantly increased (P?<?0.05) plant nutrient (N and P) acquisition and tended to increase the fruit yield. The Pc, Pl, and Fc all had additive effects on decreasing soil pH, but only Fc significantly increased (P?<?0.05) soil phosphatase activity and available P concentration, contributing partly to the elevated P acquisition as well as the increased P concentrations in both shoot and root.

Conclusions

Compared with the sole inoculation of Fc, the extra inoculation of Pl had negative effects on mycorrhizal colonization, soil P mobilization, and plant growth and nutrient acquisition. It suggests that AM fungus (Fc) has the superiority of formatting symbioses with plant roots and enhancing soil P mobilization for the suppression of pepper Phytophthora blight compared with Pl, and the joint application of different fungal agents to improve plant health needs careful consideration.

     

Effects of dolomite and gypsum on weeds

Abstract

Liming is recognized by most growers in the United States as an essential part of crop production on acid soils. Greenhouse and field studies were conducted on a sandy, siliceous, hyperthermic Ultic Hapliquod (Pomona fine sand) soil to determine the effects of dolomitic limestone and gypsum on weed populations. Under greenhouse conditions, addition of dolomite increased weed populations in pots of soil. Optimum conditions for weed growth occurred at pH 5.3 to 5.5. At pH levels greater than 5.5, weed populations were stable or showed a general decrease in number. Under field conditions, dolomite and gypsum were applied prior to plantings of three different grass species (stargrass, bahiagrass, and annual ryegrass). Addition of dolomite reduced weed populations because of a more favorable soil pH for rapid grass growth. Competition from the grasses was greater at a pH level near 5.8 to 6.0, whereas greatest weed numbers occurred at a pH of 4.8 to 4.9. Results of these studies indicate that liming is needed on acid soils for optimum crop growth, and that crops need to be established quickly as weeds are encouraged at a higher pH (5.3–5.5). Nomenclature: Stargrass, Cynodon nlemfuensis Vandersyst. var. nlemfuensis ‘Florona'; bahiagrass, Paspalum notatum Flugge ‘Pensacola'; annual ryegrass, Lolium multiflorum Lam. ‘Gulf.     

Early-season nutrient competition between weeds and soybean

Abstract

Soybean [Glycine max (L.) Merr.] yield losses may be attributable to early-season nutrient competition with weeds; however, research investigating macro- and micronutrient accumulation of weeds in soybean is scarce. Field experiments were conducted across eight site-years in Illinois, USA to determine which soybean nutrients are most susceptible to weed competition. Weeds were controlled by applying glyphosate at 10-, 20-, 30-, or 45-cm weed heights during which accumulation of 11 nutrients were measured in soybean and broadleaf and grass weeds. For both weed groups, K and Fe were the macro- and micronutrient, respectively, with the greatest rate of accumulation. Variations in nutrient uptake between broadleaf and grass weeds were largely explained by differences in weed density, except for Ca and B, which were greater in broadleaf weeds regardless of density. Canonical discriminant analysis (CDA) identified soybean accumulation of N, P, K, Fe, and Cu as the nutrients most affected by weed competition, with P, K, and Fe uptake being particularly susceptible during droughty conditions. The weed height causing a 10% reduction in uptake was 11, 12, 12, 7, and 10?cm for N, P, K, Fe, and Cu, respectively. Soybean grain yield, seed weight, pods plant^?1, and seed oil content were identified through CDA as the yield parameters most affected by weed competition. Results indicate weeds should be removed before reaching 18?cm (V2 to V3 soybean) to avoid a 5% loss in grain yield. Early-season weed control preserves yield potential and may improve efficiency of nutrient management programs in soybean.     

施钾对有些茄科作物产量和品质的影响

Over a period of two years,field experiments were conducted on wto silty loam soils grown with four solanaceous vegetable crops of geggplant(var.serpentinum Bailey),tomato(var.commune Bailey),sweet pepper(var.grossum Bailey) and chilli (var.lengum Bailey),respectively,Each experiment included four treatments with from low to high doses,0-450 kg ha^-1 for eggplant ,tomato and sweet pepper,and 0-270 kg ha^-1 for chilli,of K fertilizers in the from of sulfate of potash(SOP) applied together with N and P fertilizers. One CK treatment without K,N and P fertilzers applied and one treatment of K fertilizer in the form of muriate of potash(MOP) applied at the high level(450kg ha^-1) together with N and P fertilizers were included in the experiments of eggplant,in order to compare the effects of SOP and MOP,The fruit yields of the tested crops increased significantly with the increasing rate of K application.The crops supplied with K fertilizers yielded more stably as the CV% of their yields decreased with the rate of K application,The K fertilizers yielded more stably as the CV% of their yields decreased with the rate of K application,The dry matter and vitamin C contents in fruits of tomato,sweet pepper and chilli,and the sugar content and the titratable acidity level of tomato fruits were increased,and the S/A ratio( ratio of sugar content to titratable acidity) of tomato fruits were decreased by K fertilization,indicating that K fertilization could improve the fruit quality of the solanaceous vegetable crops.However,the high rate of Kfertilizer might lower the dry matter and vitamin C contents of tomato fruits and sewwt pepper fruits.SOP was more effective than MOP in increasing the yield and quality of eggplant fruits at the high fertilization rate;therefore,the choice of applying SOP may be better for high levels of K fertilization.     

Growth of Tropical Legume Cover Crops as Influenced by Nitrogen Fertilization and Rhizobia

Tropical legume cover crops are important components in cropping systems because of their role in improving soil quality. Information is limited on the influence of nitrogen (N) fertilization on growth of tropical legume cover crops grown on Oxisols. A greenhouse experiment was conducted to evaluate the influence of N fertilization with or without rhizobial inoculation on growth and shoot efficiency index of 10 important tropical cover crops. Nitrogen treatment were (i) 0 mg N kg^?1 (control or N₀), (ii) 0 mg N kg^?1 + inoculation with Bradyrhizobial strains (N₁), (iii) 100 mg N kg^?1 + inoculation with Bradyrhizobial strains (N₂), and (iv) 200 mg N kg^?1 of soil (N₃). The N?×?cover crops interactions were significant for shoot dry weight, root dry weight, maximal root length, and specific root length, indicating that cover crop performance varied with varying N rates and inoculation treatments. Shoot dry weight is considered an important growth trait in cover crops and, overall, maximal shoot dry weight was produced at 100 mg N kg^?1 + inoculation treatment. Based on shoot dry-weight efficiency index, cover crops were classified as efficient, moderately efficient, and inefficient in N-use efficiency. Overall, the efficient cover crops were lablab, gray velvet bean, jack bean, and black velvet bean and inefficient cover crops were pueraria, calopo, crotalaria, smooth crotalaria, and showy crotalaria. Pigeonpea was classified as moderately efficient in producing shoot dry weight.     

Effects of Municipal Solid Waste Compost on Soil Properties and Vegetables Growth

ABSTRACT

This work investigates the impact of municipal solid waste compost (MSW-compost) application (0, 50, and 100 t/ha) on the growth, and on nutrient and trace elements content in lettuce and tomato plants grown in large, 40-L pots. Our findings showed inhibition of plants’ growth with increasing dose of MSW-compost, compared to plants receiving conventional fertilization. Growth inhibition was associated with a sharp decrease in soil NO₃–N content. On the other hand, a slower decrease in soil NO₃–N content occurred in non-planted pots amended with MSW-compost. These findings provide evidence that N immobilization and/or decreased N mineralization were responsible for inhibited growth by constraining N availability. With regard to the other macro-nutrients, K, P, Mg, Ca, and Fe, their contents in leaves of both crops were maintained at optimum levels. Higher zinc and copper content was measured in leaves of both crops but they did not exceed the optimum range for growth. No accumulation of trace elements was found in the fruits. The content of heavy metals in the tissues of plants grown in MSW-compost amended soil, remained at levels similar to those of the non-amended soil, suggesting that they do not pose a significant risk either for plant growth or public health. The findings of our study suggest that further emphasis should be given on the investigation of the factors regulating N mineralization and availability in order to avoid reductions in crop yield.     

Effects of mulching and cover cropping on soil microbial parameters in the organic growing of black currant

Abstract

Cover cropping and mulching to sustain and improve soil fertility and for weed control are common practices in organic growing systems. In this study, microbial parameters under different kinds of mulches and cover crops were analyzed in a field experiment with organically grown black currant (Ribes nigrum). The experiment comprised a combination of two mulches with bare soil as a control and two cover crops which were compared with bare soil, with and without an extra supply of organic fertilizer. Soil carbon (C) and nitrogen (N) as well as pH were unaffected by any of the treatments. The basal respiration rate was increased by mulching with wood chips throughout the four years of the experiment. During the last two years of the experiment, substrate induced respiration was also measured but was not found to be affected by any of the mulches. The potential ammonium (NH₄ ⁺) oxidation increased significantly after an initial supply of 200 kg N ha^‐1 as solid cattle manure. The increase was significantly lower under wood chips than in bare soil, although an extra 200 kg N ha^‐1 had been supplied under the wood chips. Furthermore, the black currant bushes suffered from a N deficiency in the wood chip treatment. The results showed that there was no substantial lasting build‐up of microbial biomass or organic matter content with wood chips because of lack of N, despite a large initial input of N and easily‐available C. Possible reasons for this deficiency are either increased denitrification under the wood chips or fungal translocation of N to the wood chip layer. Results from this experiment suggests that the evaluation of a few complementary biological soil parameters can be an important tool when developing sustainable growing systems and for indicating environmental stress.