Green Manure Treatments Research Articles

Green manure and long-term fertilization effects on soil zinc and cadmium availability and uptake by wheat (Triticum aestivum L.) at different growth stages

Zinc (Zn) deficiency in human populations depending on cereals as a main source of Zn is a global malnutrition problem. In this field study, we investigated the potential of green manure application to increase soil Zn availability and wheat grain Zn concentrations (biofortification) on a Luvisol with different long-term fertilizer management. We also studied cadmium (Cd), as wheat is a major contributor of this undesired non-essential element to human diets. Clover (Trifolium alexandrinum L.), mustard (Sinapis alba L.) or no green manure was grown on field plots which had been managed with farmyard manure or mineral fertilizers for 65years in Switzerland. After green manure incorporation into the soil, spring wheat (Triticum aestivum L.) was grown on all plots. The “diffusive gradients in thin films” (DGT) method and DTPA extraction were used to compare soil Zn and Cd availability among the treatments. In contrast to mustard, clover increased soil mineral nitrogen concentrations and wheat biomass; however, neither increased grain Zn concentrations. DGT-available Zn and Cd increased temporarily after both farmyard manure and mineral nitrogen fertilizer application. Higher DTPA-extractable soil Zn and Cd, lower wheat grain yields, but higher grain Zn concentrations were obtained with farmyard manure compared to mineral fertilizers, independent of the green manure treatment. Farmyard manure added Zn, Cd and organic matter that increased the soil binding capacity for Zn and Cd. The decomposition of clover residues caused higher wheat grain yields, but only marginally lower grain Zn concentrations. The absence of a stronger dilution of grain Zn was probably due to organic acid and nitrogen release from decomposing clover, which facilitated Zn uptake by wheat. The study revealed that both long- and short-term field management with organic matter alters soil Zn and Cd concentrations but that the long-term effects dominate their uptake by wheat, in Zn sufficient soil.

Effects of long-term application of different green manures on ferric iron reduction in a red paddy soil in Southern China

Dissimilatory Fe(III) reduction is an important process in the geochemical cycle of iron in anoxic environment. As the main products of dissimilatory iron reduction, the Fe(II) species accumulation could indicate the reduction ability. The effects of different green manures on Fe(III) reduction in paddy soil were explored based on a 31-year rice-rice-winter green manure cropping experiment. Four treatments were involved, i.e., rice-rice-milk vetch (RRV), rice-rice-rape (RRP), rice-rice-rye-grass (RRG) and rice-rice-winter fallow (RRF). Soils were sampled at flowering stage of milk vetch and rape (S1), before transplantation (S2), at tillering (S3), jointing (S4), and mature (S5) stages of the early rice, and after the harvest of the late rice (S6). The contents of TFeHCl (HCl-extractable total Fe), Fe(II)HCl (HCl-extractable Fe(II) species) and Fe(III)HCl (HCl-extractable Fe(III) species) were measured. The correlations among those Fe species with selected soil environmental factors and the dynamic characteristics of Fe(II)HCl accumulation were investigated. The results showed that TFeHCl in RRF was significantly higher than those in the green manure treatments at most of the sampling stages. Fe(II)HCl increased rapidly after the incorporation of green manures in all treatments and kept rising with the growth of early rice. Fe(II)HCl in RRG was quite different from those in other treatments, i.e., it reached the highest at the S2 stage, then increased slowly and became the lowest one at the S4 and S5 stages. Fe(III)HCl showed oppositely, and Fe(II)HCl/Fe(III)HCl performed similarly to Fe(II)HCl. The maximum accumulation potential of Fe(II)HCl was significantly higher in RRF, while the highest maximum reaction rate of Fe(II)HCl accumulation appeared in RRG. Significant correlations were found between the indexes of Fe(II)HCl accumulation and soil pH, oxidation-reduction potential (Eh) and total organic acids, respectively. In together, we found that long-term application of green manures decreased the TFeHCl in red paddy soils, but promoted the ability of Fe(III) reduction, especially the ryegrass; Fe(II)HCl increased along with the growth of rice and was affected by soil conditions and environmental factors, especially the water and redox ability.

Comparing Green Manures in No‐till Crop Sequence

Interseeded clover. Photo courtesy of Heather Karsten. Farmers use “green manure” to protect soil, fix nitrogen, and scavenge nutrients when cash crops are not present. These cover crops can also reduce weeds and act as a mulch for cash crops in no-till systems. Because of the increasing use of cover crops in no-till systems, researchers at Penn State recently compared two green manure cover crops, red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth). “One of the reasons that we compared these was that farmers have started interseeding red clover,” says ASA member Heather Karsten, Associate Professor of Crop Production/Ecology. Interseeding, she explains, is also called relay cropping where farmers frost seed or drill red clover into a small grain very early in the spring. Karsten is a co-author on a study recently published in Agronomy Journal, titled “Green Manure Comparison between Winter Wheat and Corn: Weeds, Yields, and Economics.” The authors report that red clover treatments were more profitable than hairy vetch due to increased cash crop yield and reduced herbicide application. Dr. William Curran, Weed Extension Specialist and ASA member, had done prior research using hairy vetch in organic farming systems. As a co-author on this paper, Curran says, “I went into this thinking hairy vetch would be the winner … the results of this study surprised me a little bit.” The experiment was conducted at the Russell E. Larson Agricultural Research Station in Pennsylvania. From 2010 to 2013, green manures were used in a winter cereal–green manure–corn silage rotation. As Karsten mentioned, the red clover treatment was interseeded into the cereal grain crop whereas the hairy vetch, which was combined with triticale, was planted after the wheat harvest. Red clover was harvested for hay in late fall before corn was planted the following spring, and both cover crop treatments were terminated with herbicide in spring prior to corn planting. Corn yields were consistently greater in red clover treatments. The difference was significant in 2012 and 2013 when corn yields were 16 and 9% greater, respectively, in red clover treatments compared with hairy vetch. “We don't have all the explanations for why,” admits Karsten, but she says in 2012 and 2013, corn populations were significantly higher after red clover, and corn pest populations appear to be the culprits although there may also have been more nitrogen available from clover. View the open access Agronomy Journal article, “Green Manure Comparison between Winter Wheat and Corn: Weeds, Yields, and Economics,” online at https://doi.org/10.2134/agronj2016.02.0084 There was little difference in weed control, measured as weed biomass, between the two green manure treatments. However, red clover required fewer herbicide applications in the spring, amounting to a 28% reduction in herbicide active ingredient use. “Anytime you can use less herbicide, it's an advantage,” says Curran, both economically by reducing costs, and ecologically by reducing selection for herbicide-resistant weed biotypes. The economic benefits of increased yield, reduced herbicide, and harvesting red clover as forage were calculated as $1,355/ha more in net returns compared with hairy vetch. Even without the harvest of red clover for forage, the red clover treatments would have $123/ha greater profit than hairy vetch. The results of this study may lead more farmers, agronomic consultants, and educators to consider the use of red clover as a green manure. “I know of conventional and organic dairy and grain farmers in Pennsylvania and New York who relay crop red clover into wheat before corn,” Karsten says. “And now, we have multiple reasons to recommend red clover over hairy vetch to more growers.” Although red clover was the higher-performing green manure in this system, the authors point out that there are some limitations. Karsten explains that if wheat fields have high weed pressure, “then this interseeding might not be the best practice, but if weed populations are manageable and the typical sequence does involve rotating to corn, then we think this is a good strategy.” Cover crops are not a cure-all and need to be used strategically. Before starting to use green manure, Curran advises farmers to “really think through the process,” meaning that farmers should take into account what benefits they hope to gain from using a green manure and how they will manage both the green manure and cash crops throughout the growing season.

English

Methane (CH4) emissions from Chinese paddy soil (Zhejiang province) were measured over the rice growing seasons. Different fertilizers (organic and chemical) were applied, emissions of methane were high during two periods (05 days after peak tillering and 07 days after heading flowering stage) and significant effects of fertilizers were observed. Methanogenic activities in soils treated with organic manure were obviously higher than those with chemical fertilizers. Among the organic manure fields the maximum methane emission from green manure, biogas residue and beef manure treatment were 52, 20 and 19 times, respectively of that given by control, and among chemical fertilizers it was NH4HCO3 > CO(NH2)2 > (NH4)2SO4 > NH4Cl >NaNO3 with 2.4, 2, 1.5, 1.3, and 0.2 times, respectively of that from control. Key words: Methane emission, field, methanogenic flora flooded rice, organic and chemical fertilizers.

Physical and Chemical Properties of a Sandy Loam Soil Under Irrigated Rice-Wheat Sequence in the Indo-Gangetic Plains of South Asia

Resource conservation technologies (RCTs) such as zero tillage (ZT), dry direct seeded rice (DSR) and crop residues as mulch are known to increase productivity and profitability of rice-wheat system (RWS) in South Asia. There are, however, few studies on assessing the effect of RCTs on physical and chemical properties of soil under RWS. A field experiment on a sandy loam soil was conducted on RWS for two years at Modipuram, India involving six treatment combinations of three tillage and crop establishment methods in rice, (i) conventional puddled transplanted rice (CT-PTR), (ii) conventional dry tillage followed by direct seeding of rice (CT-DSR), and (iii) zero tillage followed by direct seeding of rice (ZT-DSR), and two green manuring options (with and without intercropping of Sesbania aculeata, -S or +S). In the succeeding wheat, rice residue (RR) was retained in sesbania green manure treatments and it was removed from no sesbania plots. Wheat was direct sown after ZT (DSW) in all the plots. Substituting PTR/ DSW without crop residues with ZT-DSR/DSW plus residue cycling reduced electrical conductivity from 0.146 dS mA¢Â€Â’1 to 0.128 dS mA¢Â€Â’1 and increased soil organic C from 5.72 g kg-1 to 6.25 g kg-1 in 0-15 cm layer. Similarly, water-stable aggregates (WSAs) >0.25 mm were 28% higher and their mean weight diameter increased by 11.9% in ZT-DSR/ DSW plus residues compared to PTR/DSW without crop residues plots. On average, there was a 23.6% increase in large (4.75-8.00 mm) aggregates and a reduction of 15.8% in finer (0.106A¢Â€Â’0.25 mm) aggregates in residue retention treatments over the no-residue treatments. In plots without puddling (ZT-DSR), the infiltration rates were higher (2.97-3.34 mmh-1) than in the CT-PTR (2.41-2.62 mmh-1). Residue retention compared to residue removal not only increased available K contents from 110.5 to 129.2 kg ha-1 but also showed favorable effects on soil matric potential and soil temperature during the wheat season. These beneficial effects on soil quality in just two years after introducing conservation tillage and residue management practices demonstrate potential to improve the long-term productivity and profitability of the RWS. However, the increased rate of infiltration under ZT with residue retention needs new irrigation techniques to minimize the loss of water through percolation during rice season.

Thirty-one years of rice-rice-green manure rotations shape the rhizosphere microbial community and enrich beneficial bacteria

Green manure rotation is commonly used to increase soil fertility and improve crop yield. However, the effects of this management practice on the underground microbial ecosystem and the indirect impact on the aboveground crop growth have not been systematically analysed. In this study, we investigated the rice rhizosphere and bulk soil microbial community in a 31-year-old field experimental site treated with different green manures and rice rotations using both 16S rDNA high-throughput sequencing and quantitative PCR approaches. Four treatments have been setup in this experimental site since 1982, including a rice-rice-winter fallow treatment as a control and three green manure rotation treatments: rice-rice-Chinese milk vetch, rice-rice-rape and rice-rice-ryegrass. The qPCR results showed that the bacterial abundances in the rice rhizosphere of the green manure rotation treatments were all significantly higher than in the winter fallow (p < 0.05), but no significant differences were found among those three green manure rotation treatments. Moreover, α-diversity analysis revealed that green manure rotations decreased the microbial diversity (Shannon and Simpson indexes) and richness (Chao value) in the rice rhizosphere. Permutational Multivariate Analysis of Variance based on β-diversity revealed the microbial community was significantly switched in rice rhizosphere after long-term green manure rotation (p < 0.01). Additionally, the soil and plant characteristics contributed almost equally to the rhizosphere bacterial community based on a partial CCA-based variation partitioning analysis. At the genus level, the well-known plant-growth-promoting rhizobacteria Acinetobacter (31%–41%) and Pseudomonas (14%–28%) were the preponderant groups in green manure rotation treatments but accounted for only 4.4% and 2.5% in the winter fallow treatment. Overall, long-term rice-rice-green manure rotation shaped the microbial community in the rice rhizosphere; in particular, some beneficial bacteria, Acinetobacter and Pseudomonas, accumulated in the rhizosphere of green manure treatments.

Durum Wheat Productivity in Response to Soil Water and Soil Residual Nitrogen Associated with Previous Crop Management

Green manure may have potential uses in dryland agroecosystems. This study determined the effect of green manure on residual soil water and soil N and the subsequent durum wheat (Triticum turgidum L.) performance in comparison with the effect of preceding dry pea (Pisum sativum L.), silage pea (Pisum sativum L.), and spring wheat (T. aestivum L.). Three green manures [black lentil (Lens culinaris Medik.), chickling vetch (Lathyrus sativus L.), and forage pea (Pisum sativum L.)] were grown in 2006, 2007, and 2008, along with pea, wheat, and a summerfallow (check) in Saskatchewan, Canada. Durum wheat was grown the year after these treatments. At durum wheat planting, the green manure treatments had the same amount of water in the 0‐ to 1.2‐m soil profile as the summerfallow in 2007 and 2009 but less water compared with the summerfallow in 2008. Summerfallow provided highest soil N among all treatments in 2007 and 2008 but lower soil N than green manure treatments in 2009. Green manure treatments increased subsequent durum wheat grain yield by 19% compared with preceding silage pea or dry pea and by 54% compared with preceding spring wheat but decreased yield by 12% compared with summerfallow treatments. The green manure with late planting and termination enhanced soil‐water conservation and offered input‐saving advantages compared with the early‐ and mid‐planting and termination treatments. Overall, green manure treatments enhanced soil water storage, provided N benefits, and increased subsequent durum wheat yield compared with crops harvested for grain.Core Ideas Green manures conserve a similar amount of water in the 0‐ to 1.2‐m soil profile as summerfallow. Green manures provides less N benefits as summerfallow to the crops the following year. Durum wheat after green manures yielded 19 to 54% more than the other preceding crops. Delay planting of green manures offers water‐saving advantages in dry environments.

Effect of organic by-products amendments on quality of heavy metal-contaminated soil treated using aided phytostabilization

In organic farming it is crucial to reach the best compromise between yield and sustainability of agronomical strategies. To this end, this two-year study evaluated the effects of legume cover crop management (no cover; vetch grown as green manure; roller crimped vetch) and organic amendments (no fertilizer; compost; animal manure; digestate fertilizer) application on organic transplanted zucchini and weed biomass productions, N dynamics, N balance and competitive interactions. In the first year, the vetch incorporated as green manure treatment showed the highest zucchini yield and weed biomass, as well as the highest crop N uptake reduction in presence of weeds. The roller crimped cover crop showed a decrease in weed biomass by more than 65% compared to green manure, and higher productivity than the no cover treatment. Animal manure and digestate fertilizers showed the highest yield, soil mineral N contents and crop N uptake, even if no variation in competitive ability was recorded. Conversely, the second year showed the potential limits of the roller crimping technique under cooler conditions, implying a reduction in zucchini yield performances and competitive ability. Among the experimental fertilizers, the digestate showed comparable results than commercial fertilizer for yield, but significantly higher than N0 (by 31%) and, when combined to vetch management, also in terms of N balance. This study illustrates the effectiveness of combination of different agronomical strategies to obtain adequate yield and weed impact reduction.

Green manure crops for integrated pest management in upland taro fields in Hawaii

Taro (Colocasia esculenta) is a non-graminaceous monocot consumed primarily for its starchy corm. To determine the best green manure crops to rotate with upland-grown taro, 10 genotypes of seven green manure species were evaluated in a greenhouse study to determine their ability to suppress root-knot nematode Meloidogyne javanica. These species were: black hollyhock (Alcea rosea L.); canola (Brassica napus L.); cabbage (B. oleracea L.); French marigold (Tagetes patula L.), sorghum-sudangrass [Sorghum bicolor (L.) Moench nothosubsp. drummondii (Steud.) de Wet ex Davidse]; sunn hemp (Crotalaria juncea L.); and yellow mustard (Sinapis alba L.). Plants were inoculated with eggs of M. javanica and after 6 weeks, nematode eggs, and reproduction factor (Rf) of M. javanica were determined. Marigolds were non-hosts to M. javanica; other crop species that were poor hosts to M. javanica included canola 'Dwarf Essex', sorghum-sudangrass cvs. Piper and Sordan 79, black hollyhock 'Nigra', and sunn hemp. Based on results of this greenhouse study, eight green manure treatments (yellow mustard cultivar 'Ida Gold', French marigolds cultivars 'Nema-gone' and 'Golden Guardian', sorghum-sudangrass cultivar 'Sordan 79' and 'Tastemaker', sunn hemp, an unplanted plot, and a clean fallow control plot) were selected and grown for 3 months in a field trial in Pepeekeo, Hawaii. Each treatment was blocked four times in a randomized complete block design. Based on this field trial, marigold cultivars, sorghum-sudangrass hybrids, and sunn hemp appeared to be the best green manure crops for rotation in an upland taro cropping system.

Measurement of Nitrous Oxide Emissions on the Cultivation of Soybean by No-Tillage and Conventional-Tillage in Upland Soil

The impact of 1 pound of nitrous oxide (N₂O) on warming the atmosphere is almost 310 times that of 1 pound of carbon dioxide. Agricultural soil management is the largest source of N₂O emissions, accounting for about 73% of total N₂O emissions. This study was conducted to evaluate the nitrous oxide emission in the cultivation of soybean during the first year of No-tillage (NT) and Conventional-tillage (CT) practices, under the various conditions such as different kinds of fertilizers, soil temperature, and moisture level. In the experiment, we set CT and NT treatments into 4 different groups - control treatments (no fertilization), green manure treatments, chemical fertilizer treatments and organic manure treatments. In the case of chemical fertilizer treatments, N₂O emission of NT treatment was 7.78 to 22.59% lower than CT treatment. In organic manure treatment, N₂O emission of NT treatment was 6.62% higher than CT treatment in August. But In July and September, N₂O emission of NT treatment was 9.50% 28.38% lower than CT treatment, respectively. Soil temperature was correlated with N₂O emission positively. In the future, continued long-term research on influence of various environmental factors on the generation of N₂O and the economic value of no-till farming is required.

Long-term rice-rice-green manure rotation changing the microbial communities in typical red paddy soil in South China

On the basis of a long-term (30 years) field experiment that involved four rotation systems, rice-rice-winter fallow (RRF), rice-rice-ryegrass (RRG), rice-rice-rape (RRP), and rice-rice-milk vetch (RRV), this study described the effects of green manure on the microbial communities in the red paddy soils using 454 pyrosequencing for the 16S rRNA gene. The Chao1 richness and non-parametric Shannon's index increased in all soil samples that received green manure treatments. The communities’ structures with the green manure applications were significantly dissimilar from that under the winter fallow. Using Metastats tests, many genera in the RRG, RRP and RRV soils were significantly different from those in the RRF soil, including a number of genera that functioned in the nitrogen and sulfur cycles. Analyses of the genera with these functions revealed the shifts in microbial ecosystem functions after long-term green manuring. Changes in the microbial communities increased the ammonium supply and decreased the soil acidification in green-manure-amended soils. Together, these data suggested powerful effects of green manure on both the microbial communities and the biogeochemical cycle driven by the shifts in bacterial functional groups.

Fertility practices and rhizosphere effects alter ammonia oxidizer community structure and potential nitrification activity in pepper production soils

Increasing nitrogen use efficiency is critical to the productivity and long-term sustainability of vegetable production systems in the US Midwest. Understanding the impact of alternative fertility sources on the ecology of the soil nitrogen cycle has potential to allow for management that will increase crop N uptake and reduce loss. We determined how repeated applications of urea, composted chicken litter, hairy vetch green manure with alfalfa meal, and an unfertilized control affected the structure and potential nitrification activity (PNA) of ammonia oxidizers in bulk and rhizosphere soil when N needs were expected to be high. PNA was greater in animal and green manure treatments relative to urea and the unfertilized control in bulk soil, and greater in the rhizosphere relative to bulk soil regardless of fertility treatment. A strong correlation was observed between PNA and ammonia oxidizing bacteria (AOB) abundance, suggesting that AOB rather than ammonia oxidizing archaea (AOA) controlled nitrification in this system. However, AOB abundance did not differ between bulk and rhizosphere soil, and PNA was lower in the urea treatment despite greater AOB abundance indicating that other factors could have affected PNA. For example, greater availability of labile carbon (C) could have stimulated PNA through various mechanisms, and lower pH and/or specific nitrification potential per AOB cell could have reduced PNA in the urea treatment. AOB community structure was more diverse in all fertility treatments relative to the unfertilized control in bulk soil, and community structure differed between bulk and rhizosphere soil indicating niche differentiation. However, differences in AOB community structure and PNA were only observed in rhizosphere relative to bulk soil indicating that the rhizosphere had a greater effect on nitrification dynamics than fertility practices. These findings indicate that organic fertility amendments stimulate PNA, but they could also increase N loss and should be investigated further. The rhizosphere appears to play a greater role in nitrification dynamics than fertility practices, and more detailed investigations at this key plant-soil interface are warranted.

Direct seeding of Brazilian savanna trees: effects of plant cover and fertilization on seedling establishment and growth

Direct seeding is a promising technique for ecological restoration, but it has been poorly studied in neotropical savannas. Different types of plant cover (no cover, crops, or green manure) and fertilization (unfertilized, synthetic fertilizer, or poultry litter) were used to verify if survival and growth of different tree species after direct seeding could be enhanced by the use of any combination of these techniques. Seedling emergence, establishment, and growth were followed for 2 years for six savanna tree species sown in an agricultural field in Central Brazil. Germination was high (52%, on average) for Anacardium occidentale, Aspidosperma macrocarpon, Hymenaea stigonocarpa, Dipteryx alata, Eugenia dysenterica, and Magonia pubescens. Six additional species were planted, but less than 5% of these seeds germinated. Crops (60% shade) did not affect seedling survival and biomass compared with the control treatment, supporting the use of this strategy during the initial phase of restoration to involve farmers in the process. In contrast, the excessive shading (95%) from the green manure treatment decreased the survival of two species and the growth in biomass and diameter of five species, especially when combined with fertilization. Seedling growth was very slow throughout the experiment, requiring extended weed management. This study supports the use of direct seeding of the studied species for savanna restoration, but methods could be improved to include a larger number of species.

The effect of green manures and nitrogen fertilizer on yield, yield components and nitrate accumulation of potato tuber

In a two years research, the effect of green manures and nitrogen fertilizer on tuber number, mean tuber weight and tuber yield of potato was investigated. The experiment was carried out as split plot based on a randomized complete block design with three replications. Green manure treatments of barley, canola, clover, vetch and without green manure were allocated to the main plots and nitrogen fertilizer levels of 100, 75, 50 and 25% of recommended fertilizer to sub-plots. Results of each year were statistically analyzed separately and also combined. The effect of green manure and nitrogen fertilizer on the tuber nitrate concentration, number of tubers per plant and mean tuber weight was significant at 1% and also on the tuber yield at 5%. All the green manure treatments increased tubers nitrate within permissible limit. The clover with 75% of recommended nitrogen showed a significant difference with the control (p≤1%) and resulted in 34% increase in the number of tubers per plant, and 25% decrease in nitrogen consumption; and in the term of mean tuber weight, the vetch with 100% of recommended nitrogen was the best treatment and it had significant difference with the control at 1% and resulted in 17% increase in mean tuber weight. Moreover, the interaction of clover with 75% of nitrogen was the best treatment in terms of tuber yield and it had significant difference with the control at 1% and resulted in a 33% increase in tuber yield, and in addition, it decreased nitrogen consumption by 25% .

Effect of roller-crimper technology on weed management in organic zucchini production in a Mediterranean climate zone

AbstractIntegrating cover crops into vegetable cropping systems can provide a wide range of ecological services, of which weed management is a key component. Cover crop effects on weed control, however, are dependent on termination methods and weed species present in specific cropping seasons. A 2-year weed management experiment with two cultivars of organic zucchini (Cucurbita pepo L.) in central Italy was carried out to compare the effect of a barley (Hordeum distichum L.) cover crop terminated with a modified roller-crimper (RC) to incorporated barley as green manure (GM) and a tilled control left fallow (FA) in the off-season. The effects of cover-crop management on crop competitiveness, yields and weed populations were evaluated by direct measurement, visual estimation and competition index methods. Results showed a significant reduction in weed biomass (&gt;80%) and weed abundance with the RC compared to the GM and FA treatments. Moreover, the RC barley mulch maintained weed control in zucchini plots even under high weed pressure, as determined by the agronomic tolerance to competition (ATC) value of 67% in the RC treatment compared to 40 and 34% in the FA and GM treatments, respectively, averaged over both years of the experiment. The competitive balance (Cb), which quantified the ability of the zucchini crop to compete with weed populations, was also greater (+0.37) in the RC treatment compared to FA (−0.87) and GM (−0.69) treatments over the same period. Zucchini crop biomass was greatest in the RC treatment in 2011. Zucchini fruit yields varied from an average over both years of 1.4 Mg ha−1 in the RC treatment to 0.7 Mg ha−1 in the GM treatment, but yields in the FA treatment, 1.2 Mg ha−1, did not differ from the RC treatment. No differences in yield between ‘Dietary’ and ‘Every’ zucchini, or any significant interactions between cultivar and cover management related to fruit biomass, were observed. Our findings suggested the viability of the modified RC in creating a barley cover-crop mulch to effectively manage weeds and enhance yields in transplanted zucchini.

Impact of plastic film mulching on increasing greenhouse gas emissions in temperate upland soil during maize cultivation

Plastic film mulching (PFM) is an agricultural management practice that is commonly used to suppress weed growth. However, its effect on greenhouse gas (GHG) emissions has not been well evaluated. To investigate the effect of PFM on GHG emissions and crop productivities, black PFM and no-mulching plots were installed as the main treatment, and three sub-treatments, chemical fertilizer (NPK) and two green manures, were arranged within each main treatment. Two cover crops (hairy vetch and barley) with different carbon/nitrogen (C/N) ratios were cultivated in the two green manure treatments during the fallow season. The aboveground biomasses of vetch (23–25Mg fresh weight ha−1) and barley (10–11Mgha−1) were incorporated before maize seedling transplanting. Maize was cultivated without chemical fertilization in the two green manure treatments, whereas the recommended chemical fertilizers were applied in the NPK treatment. During two annual cropping seasons, the emission rates of methane (CH4) and nitrous oxide (N2O) gases were simultaneously monitored once a week using the closed-chamber method. Total global warming potential (GWP) was calculated as CO2 equivalents by multiplying the seasonal CH4 and N2O fluxes by 25 and 298, respectively. Irrespective of soil amendments, PFM significantly increased soil temperature and moisture content by a mean of 2°C and 0.04m3m−3 over no-mulching, respectively. Plastic film mulching increased grain productivity by 8–33% over no-mulching. However, PFM significantly decreased soil organic matter content and largely increased the two major GHG emissions. As a result, PFM increased the total GWP by 12–82% over no-mulching, irrespective of the soil amendments. In conclusion, more sustainable mulching systems should be developed that can sustain soil quality and minimize environmental impacts, including GHG emissions.

SIX YEARS OF RESULTS FROM A POTATO ROTATION AND GREEN MANURE TRIAL IN TASMANIA, AUSTRALIA

Irrigated cropping of vegetables and poppies ( Papaver somniferum ) is an important farming system in Tasmania. Green manure crops are often grown between cash crops to provide ground cover and soil organic matter and to retrieve subsoil nitrogen. A field trial was started in 2006 to assess the cumulative effects of three autumn-winter land uses: (a) fallow, and (b) annual ryegrass and (c) brassica (BioQure BQ Mulch TM ) green manures on cash crop production, soil-borne disease inoculum, and other soil properties. The three green manure treatments were established each autumn in a randomized block design. A cash crop was grown over all plots in each spring-summer period except in 2009 when plots were split to accommodate two cash crops, potatoes and onions. Because potatoes were also grown over the whole trial in 2006 and 2012, the split in 2009 allowed 3- and 6-year potato rotations to be compared. Concen¬trations of DNA in soil of the pathogens causing powdery scab, common scab, black scurf and stem canker in potatoes were measured each year, while soil carbon and other chemical properties were measured in 2006, 2009 and 2012. In potato ‘Desiree’ the 3-year potato rotation resulted in more powdery scab and lower total tuber yield than the 6-year potato rotation, the first report of such an effect for this disease. Concentrations of DNA of Spongospora subterranean , the cause of powdery scab, increased in the soil each time potatoes were grown. Concentrations of DNA of the other pathogens were little affected by the presence of potatoes or green manures, but DNA of Rhizoctonia solani AG3 was less on average in fallow compared to green manure plots. Soil carbon decreased across the whole site during the experiment but there was no statistically significant effect of green manures on soil carbon or cash crop production.

Sustaining Soil Quality in Intensively Managed High Tunnel Vegetable Production Systems: A Role for Green Manures and Chicken Litter

Use of high tunnel crop production is expected to increase to meet the growing demand for locally produced fresh market vegetables. These structures have the potential to offer many production benefits; however, managing soil quality in these structures is challenging and work in the area is limited. In this 3-year study, we compared the impacts of organic and inorganic fertility amendments on soil quality, nutrient availability, and the productivity of chard (Beta vulgaris L.) and sweet peppers (Capsicum annuum L.) produced in high tunnel and open field systems. Fertility amendments included a green manure treatment [hairy vetch (Vicia villosa Roth) and dehydrated alfalfa meal], partially composted and pelletized chicken litter, urea, and an unfertilized control. Chard was grown in 2011, and peppers were grown in 2012 and 2013. Soil nutrients, microbial activity, active carbon, pH, electrical conductivity (EC), total soil organic matter, and yield were quantified. Chard yield was lower in the high tunnel compared with the open field in 2011, but pepper yield was greater in the high tunnel in 2012 and 2013. Productivity of chard was lower in the green manure compared with urea in 2011 across high tunnel and open field production systems, but no difference in pepper yield was observed between plants receiving fertility inputs in either 2012 or 2013. Repeated application of green manure and chicken litter resulted in soils with increased microbial activity and active carbon, but the green manure was the only treatment successful at accruing carbon in the high tunnel over time. High tunnel production resulted in greater EC compared with the open field, but levels were not considered inhibitory for chard or peppers. High tunnels can increase vegetable crop productivity in the midwest United States, and organic fertility amendments can improve soil quality as measured by soil microbial activity and active carbon in high tunnel and open field production systems.

Legume cover crop management and organic amendments application: Effects on organic zucchini performance and weed competition

In organic farming it is crucial to reach the best compromise between yield and sustainability of agronomical strategies. To this end, this two-year study evaluated the effects of legume cover crop management (no cover; vetch grown as green manure; roller crimped vetch) and organic amendments (no fertilizer; compost; animal manure; digestate fertilizer) application on organic transplanted zucchini and weed biomass productions, N dynamics, N balance and competitive interactions. In the first year, the vetch incorporated as green manure treatment showed the highest zucchini yield and weed biomass, as well as the highest crop N uptake reduction in presence of weeds. The roller crimped cover crop showed a decrease in weed biomass by more than 65% compared to green manure, and higher productivity than the no cover treatment. Animal manure and digestate fertilizers showed the highest yield, soil mineral N contents and crop N uptake, even if no variation in competitive ability was recorded. Conversely, the second year showed the potential limits of the roller crimping technique under cooler conditions, implying a reduction in zucchini yield performances and competitive ability. Among the experimental fertilizers, the digestate showed comparable results than commercial fertilizer for yield, but significantly higher than N0 (by 31%) and, when combined to vetch management, also in terms of N balance. This study illustrates the effectiveness of combination of different agronomical strategies to obtain adequate yield and weed impact reduction.

تأثير التسميد الأخضر و الآزوتي في امتصاص و محتوى النبات من الآزوت و توزعها على الأجزاء النباتية المختلفة لمحصول القطن ضمن ظروف سهل الغاب = Effect of Green Manure and Nitrogen Fertilizer on Nitrogen Uptake , Content and Its Distribution among Different Cotton Plant Parts in Al-Ghab Plain

The research was carried out at AL-Ghab Research Center during 2009-2011 seasons using split plot design with three replications, to study the effect of mineral and Organic nitrogen fertilization on N uptake of cotton plant. Four levels of mineral nitrogen fertilization (0-80-160-240 kg N/ha) were used and five green manure treatments (GM0: without green manure, GM1: peas, GM2: Faba Bean, GM3: Vetch, GM4: Barley/Vetch mixture). The results showed that cotton crop parts responded differently to treatments, where the N content in the leaves increased significantly at all levels of the nitrogen fertilization compared with control at flowering and maturity stages in both seasons. While effect of nitrogen fertilization and green manure were not significant on the nitrogen content in stem and Fruiting Forms, while the nitrogen uptake affected by the tow kinds of fertilization significantly on all plant parts compared with control at flowering stage in both seasons, and the best treatment which gave the highest productivity was GM1N160 reaching 4784.7, 6141.1 kg/ha of cotton lint in both seasons, respectively.