Continuous Monocropping System Research Articles

Inhibition of continuous cropping obstacle of celery by chemically modified biochar: An efficient approach to decrease bioavailability of phenolic allelochemicals

The accumulation of allelochemicals released by plants is commonly found in continuous monocropping systems. These chemicals, such as phenolic acids, were shown to be the major sources of autotoxin or pathogen accumulation in soils, leading to a direct or indirect continuous cropping obstacle. In this study, three types of agricultural residuals, i.e., rice husk, tea waste, and wood meal, were chosen as feedstocks. Biochar samples were prepared from these feedstocks to examine their abilities to remove gallic acid, a representative phenolic acid. Biochar, which was prepared from wood meal soaked with H3PO4 (1:1.5, w/w) and pyrolyzed at 400 °C (symbolized as WP400), exhibited the highest adsorption capacities of gallic acids and other phenolic acids. The mechanisms of phenolic acid removal by WP400 were evaluated via experimental and spectroscopic investigations to elucidate the notable adsorption capacity of WP400. The adsorption of gallic acids was pH-dependent and followed a pseudo-second-order kinetic model. The combination of high surface area, the existence of O-containing groups, and the enhancement of H bonds between CC groups and phenolic acids may contribute to the high adsorption capacity of WP400. In a pot experiment, we found that celery growth was promoted with the addition of 0.3% (w/w) WP400 to soils that were continuously monocropped with celery. A large decrease in the water-soluble phenolic compound by more than 40% may be responsible for the results. However, WP400 scavenged nitrate, and this study showed that the synergistic actions of WP400 and nutrients exhibited the greatest efficiencies in mitigating the continuous cropping obstacles of celery.

Farm Diversification in Haryana, India: Case Studies

In the late 1960s, the Green Revolution enabled India to overcome a severe food shortage and achieve food grain self-sufficiency, particularly in the case of wheat and paddy. Continuous mono cropping system threatens the sustainability of future agricultural production in terms of soil, water, climate and market parameters which warrants a diversified farming system enabling farmers to use their resources efficiently with its ecological benefits. Recent trends in crop farming witnessed a multifold shift towards paddy and wheat specialization in Haryana. So farm diversification is an important strategy to maintain the sustainability of state agriculture. The present study was undertaken to explore the potential of farm diversification in Haryana. Case studies were conducted among selected farmers from the three districts representing three agro ecological zones of Haryana (Kaithal from AEZ1, Hisar from AEZ2 and Bhiwani from AEZ3). The case study included parameters like area and number of enterprises and cost details and net returns from each diversified enterprise. The study concludes that, various methods utilized by the successful farmers specialized in a particular venture serve as the model for fellow farmers who are similarly interested in the same experience. Subsidies, incentives and training programmes of government agencies promoted the farmers to get involved in the allied enterprises. This study highlights the need for incentives and training programmes for further promoting farm diversification in the state.

Temporal and Habitat Dynamics of Soil Fungal Diversity in Gravel-Sand Mulching Watermelon Fields in the Semi-Arid Loess Plateau of China.

Mulching is an important agricultural management tool for increasing watermelon productivity and land-use efficiency because it helps improve water use efficiency and reduce soil erosion. However, there is relatively little available information regarding the effects of long-term continuous monoculture farming on soil fungal communities and related fungal pathogens in arid and semiarid regions. In this study, we characterized the fungal communities of four treatment groups, including gravel-sand-mulched farmland, gravel-sand-mulched grassland, fallow gravel-sand-mulched grassland, and native grassland, using amplicon sequencing. Our results revealed that the soil fungal communities differed significantly between mulched farmland and mulched grassland as well as the fallow mulched grassland. Gravel-sand mulch significantly impaired the diversity and composition of soil fungal communities. Soil fungal communities were more sensitive to gravel-sand mulch in grassland than in other habitats. Long-term continuous monoculture (more than 10 years) led to decreased abundance of Fusarium species, which contains include agronomically important plant pathogens. In the gravel-mulched cropland, some Penicillium and Mortierella fungi were significantly enriched with increasing mulch duration, suggesting potential beneficial properties of those fungi that could be applied to disease control. We also found that long-term gravel mulching in continuous monoculture farming could potentially form disease-suppressive soils and alter soil microbial biodiversity and fertility. Our study provides insights into the exploration of novel agricultural management strategies along with continuous monoculture practice to control watermelon wilt disease by maintaining a more sustainable and healthier soil environment. IMPORTANCE Gravel-sand mulching is a traditional agricultural practice in arid and semiarid regions, providing a surface barrier for soil and water conservation. However, application of such practice in monocropping systems may lead to outbreaks of several devastating plant diseases, such as watermelon Fusarium wilt. Our results with amplicon sequencing suggest that soil fungal communities differ significantly between mulched farmland and mulched grassland and are more sensitive to gravel-sand mulch in grassland. Under continuous monoculture regimens, long-term gravel mulch is not necessarily detrimental and may result in decreased Fusarium abundance. However, some known beneficial soil fungi may be enriched in the gravel-mulch cropland as mulch duration increases. A possible explanation for the reduction in Fusarium abundance may be the formation of disease-suppressive soils. This study provides insight into the need to explore alternative strategies using beneficial microbes for sustainable watermelon wilt control in continuous monocropping system.

Diversity and abundance of bacterial and fungal communities in rhizospheric soil from smallholder banana producing agroecosystems in Kenya

In agroecosystems, microbial communities play a crucial role in delivery of various ecosystem services. These microbial communities are affected by several factors such as soil physicochemical properties which contribute to the diversity of bacterial and fungal communities. In this study, we investigated the soil physicochemical parameters and the diversity and abundance of bacterial and fungal communities in rhizospheric soil collected from banana growing regions in Kisii, Nyamira and Embu Counties of Kenya. Rhizospheric soil samples from the three regions showed significant differences at (P= 0.01) with the lowest recorded pH being 4.43 in Embu County. Based on Next-generation sequencing results, there was a significant diversity and abundance of bacterial division Proteobacteria while the predominant fungal division was basidiomycota, Several genera in the fungal division such as Penicillium and Cladosporium as well as bacterial genera such as Acidobacterium and Pseudomonas sp. were those associated with soil. There were several plant pathogenic and beneficial bacteria and fungi. Based on redundancy analysis (RDA) the distribution of these microbes was affected negatively by soil parameters such as total organic carbon (TOC) and pH. In conclusion, Soil health and continuous mono-cropping systems play a significant role in the diversity and abundance of both beneficial and harmful soil microbes. Metagenomics approaches in studying microbial communities in agroecosystems is a revolutionary approach which will aid in the development of sustainable tools in agriculture that improve microbiome structures as well as overall productivity.

Soil Macrofauna Abundance and Taxonomic Richness under Long-Term No-Till Conservation Agriculture in a Semi-Arid Environment of South Africa

Soil macrofauna are a critical component for ecosystem function and strongly affect production sustainability. The effect of fertiliser management practices, in different cropping systems, on soil macrofauna communities remains poorly understood in semi-arid to arid regions. The objective of this study was to investigate the effect of tillage practices i.e., no-till (NT), rotational tillage (RT) and conventional tillage (CT) and nitrogen fertiliser application rates (0, 100 and 200 kg/ha N) (urea) on abundance and order diversity of soil macrofauna in a maize continuous monocropping system. The sampling of macrofauna in the trial was conducted in April 2019, August 2019 and March 2020 using 25 cm × 25 cm × 25 cm steel monoliths in randomly selected positions, and this was replicated four times. The study found a significant (p < 0.05) increase in the abundance of soil macrofauna in NT (127 ind/m2) and RT (110 ind/m2) compared to CT (51 ind/m2) treatment. The abundance of macrofauna was also negatively affected by increasing the rate of fertiliser, with 0, 100 and 200 kg/ha resulting in 133, 94 and 62 ind/m2. Orders Haplotaxida and Diplopoda were found to be sensitive to increases in the fertiliser application rate. Haplotaxida (48.4%) was the most abundant order, followed by Coleoptera (18.2%). Other orders included Diplopoda (9.2%), Gastropoda (6.3%), Isoptera (4.7%), Chilopoda (4.7%), Araneae (4%), Hymenoptera (3.2%), Orthoptera (0.9%) and Dermaptera (0.3%). No-till (NT) and rotational tillage (RT) with mulch favoured the establishment of various macrofauna communities in the studied cropping system.

Temporal Bacterial Community Diversity in the Nicotiana tabacum Rhizosphere Over Years of Continuous Monocropping.

Long-term continuous monocropping negatively influences the physicochemical and biological characteristics of cultivated soil, especially for the economically important crop of flue-cured tobacco that is intolerant to continuous monocropping. The underlying mechanism of soil sickness under continuous monoculture and the temporal dynamic changes over the tobacco life cycle among different monoculture time spans remain poorly characterized. In this study, high-throughput sequencing targeting the 16S rRNA gene phylogenetic marker was performed on 60 soil samples of rhizosphere soil from flue−cured tobacco in the replanting, growth and harvest period across 5, 10, and 20 years of a continuous monocropping system. Bacterial community diversity decreased with the increase in duration of continuous monocropping, and the rhizosphere microbiota was highly dynamic in the harvest period. The random forests algorithm identified 17 taxa as biomarkers and a model was established to correlate root microbiota with continuous monocropping time of flue-cured tobacco. Molecular ecological network analysis elaborated the differences and interactions in bacterial co-occurrence patterns under different monocropping systems. The co-occurrence microbial network was larger in size but there were fewer interactions among microbial communities with the increase in continuous monocropping duration. These results provide insights into the changes of flue−cured tobacco root microbiome diversity in response to continuous monocropping and suggest a model for successional dynamics of the root-associated microbiota over continuous monocropping time and development stage. This study may help elucidate the theoretical basis underlying obstacles to continuous monocropping and could contribute to improving guidance for tobacco production.

Influence of No-Tillage on Soil Organic Carbon, Total Soil Nitrogen, and Winter Wheat (Triticum aestivum L.) Grain Yield

No-tillage (NT) can improve soil properties and crop yield. However, there are contrasting reports on its benefits compared to conventional tillage (CT). Dataset (2003–2018) from long-term continuous winter wheat (Triticum aestivum L.) experiments 222 (E222) at Stillwater and 502 (E502) at Lahoma in Oklahoma, USA, established in 1969 and 1970, respectively, was used. Both experiments were managed under CT until 2010 and changed to NT in 2011. In each tillage system, treatments included nitrogen (N) rates at E222 (0, 45, 90, and 135 kg·N·ha−1) and E502 (0, 22.5, 45, 67, 90, and 112 kg·N·ha−1). The objective was to determine the change in wheat grain yield, soil organic carbon (SOC), and total soil nitrogen (TSN) associated with the change to NT. Grain yield was recorded, and postharvest soil samples taken from 0–15 cm were analyzed for TSN and SOC. Average TSN and SOC under NT were significantly above those under CT at both locations while grain yield differences were inconsistent. Under both tillage systems, grain yield, TSN, and SOC increased with N rates. At E222, grain yield, TSN, and SOC under NT were 23%, 17%, and 29%, respectively, more than recorded under CT. At E502, grain yield was lower under NT than CT by 14% while TSN and SOC were higher by 11% and 13%, respectively. Averaged over experimental locations, wheat grain yield, TSN, and SOC were 5%, 14%, and 21%, respectively, higher under NT compared to CT. Therefore, NT positively influenced grain yield, TSN, and SOC and is likely a sustainable long-term strategy for improving soil quality and crop productivity in a continuous monocropping system.

Productivity, Nutrient, and Soil Enzymes Influenced with Conservation Agriculture Practices in Peanut

Core Ideas Peanut–wheat–Sesbania cropping system recorded the highest peanut–pod equivalent yield.Peanut–wheat–Sesbania/ green gram markedly increased soil enzymatic activities.Bulk density decreased in peanut‐CTW and peanut + pigeonpea crop rotations. Peanut (Arachis hypogaea L.) is a soil‐C depleting crop under a continuous monocropping system. A study was conducted comprising combinations of tillage practices (zero tillage [ZT] or conventional tillage [CT]), crop rotation (sole peanut, peanut‐wheat [Triticum aestivum L.], or peanut+pigeonpea [Cajanus cajan L.]), and green manuring (GM) (green gram [Vigna radiata L.], sesbania [Sesbania aculeata Willd.], or wheat straw incorporation [WSI]). Peanut pod yield was found higher in peanut followed by wheat either zero tilled (ZTW) or conventional tilled (CTW), and GM either with sesbania/green gram/WSI. Green manuring in peanut–ZTW and peanut+pigeonpea recorded higher grain yield of wheat (3.11 t ha−1) and pigeonpea (1.76 t ha−1), respectively. Sesbania GM increased root biomass of peanut, wheat, and pigeonpea in all the systems. Peanut‐pod equivalent yield recorded significantly higher in peanut–ZTW or CTW when included GM with either sesbania or green gram (3.64 t ha−1). Found higher accumulation of soil N in peanut–ZTW–sesbania (33.8 kg ha−1), P in peanut–CTW (6.4 kg ha−1), and S in peanut–CTW (3.7 kg ha−1) crop rotations. Activities of urease, β‐glucosidase, acid phosphatase, and alkaline phosphatase were increased in all the crop rotations that included green manuring or WSI over sole peanut. Soil bulk density (0–15 cm depth) was recorded lower in peanut–CTW, however, higher in peanut–ZTW. Peanut followed by ZTW or CTW and green manuring either with sesbania or green gram found more sustainable than sole peanut in terms of peanut‐pod equivalent yield and improved soil enzyme activities.

Long-term simulation of temporal change of soil organic carbon in Denmark: comparison of three model performances under climate change

AbstractThe temporal change in soil organic carbon (SOC) was analysed over an 80-year period based on climate change predictions of four regional circulation models under the International Panel on Climate Change (IPCC) A1B emission scenario in the 21st century. A 20-year (1991–2010) set of observed climate data was used to form the baseline, and generate synthetic data for future scenario analyses. With increasing carbon dioxide (CO2) levels, and under continuous winter wheat production with conventional tillage at different nitrogen (N) input rates, three crop-soil models were used to study the temporal changes of SOC. Results indicated that soil carbon (C) generally decreased over the simulation period. In addition, increased N losses through leaching and denitrification were estimated. Decline in soil C under continuous mono-cropping systems indicated increased focus on N fertilization strategies. The results also suggested significant interactive effect of N input rate and climate variables on soil C and denitrification in response to climate change. The uncertainty was addressed by including the crop-soil models in a mixed-effect analysis so that the contribution of the models to the total variance of random variation was quantified. Statistical analysis showed that the crop-soil models are the main source for uncertainty in analysing soil C and N responses to climate change.

The long-term effect of climate change on productivity of winter wheat in Denmark: a scenario analysis using three crop models

SUMMARYThe response of grain yield, grain nitrogen (N), phenological development and evapotranspiration of winter wheat to climate change was analysed over an 80-year period based on climate change predictions of four regional circulation models (RCMs) under the IPCC (International Panel on Climate Change) A1B emission scenario for the 21st century using three process-based models; A 20-year set (1991–2010) of observed daily climate data from Aarslev, Denmark was used to form the baseline, from which the RCM data were generated. The simulation of crop growth was performed with increasing carbon dioxide (CO2) levels and under continuous mono-cropping system at different N input rates. Results indicated that grain yield and grain N will be reduced in the future despite increased CO2 concentration in the atmosphere. While the increased N input may increase yield, it will not increase grain N. The present study suggested that in Denmark, alternative strategies for organic N acquisition of plants must be developed. Statistical analyses showed that while the crop models were the main source of uncertainty in estimating crop performance indicators in response to climate change, the choice of RCM was the main source of uncertainty in relation to baseline estimations.

Identification and Bioassay of Allelopathic Substances from Plant and Rhizosphere Soil Extracts of Adzuki Bean (Vigna angularis [Willd.] Ohwi & H. Ohashi.)

<p class="Abstract">The soil sickness of Adzuki bean [<em>Vigna angularis </em>(Willd.) Ohwi & H. Ohashi] have been getting attention seriously under a continuously mono-cropping management-system in China. To investigate the allelopathy of rhizosphere soil and plant of Adzuki bean, culture dish and pot experiments were conducted. The compounds in the products were identified by High Performance Liquid Chromatography (HPLC).The aqueous extracts from rhizospheric soil and whole plant inhibited seed index (seed germination and seed potential) and plant growth under different degrees, and it showed concentration gradient effect on the inhibition of seed germination. Inhibition was stronger with increasment in extract concentration with the highest effect at 0.16 parts aqueous extract to 1 parts deionized water (0.16g·mL<sup>-1</sup>). The impact on growth varied among aqueous extracts from rhizospheric soil and the whole plant. Five phenolic compounds, cinnamic, phthalic, <em>p</em>-hydroxybenzoic, and isobutyricand glutaric acids, were detected from the rhizosphere soil and plant extract of Adzuki bean by HPLC method. Cinnamic, phthalic, and <em>p</em>-hydroxybenzoicacids were higher than that of the other phenolic acids. This result suggests that autotoxicity effects of phenolics on Adzuki bean probably happen in continuous mono-cropping systems.</p>

Responses of Soil Microbial Communities in the Rhizosphere of Cucumber (Cucumis sativus L.) to Exogenously Applied p-Hydroxybenzoic Acid

Changes in soil biological properties have been implicated as one of the causes of soil sickness, a phenomenon that occurs in continuous monocropping systems. However, the causes for these changes are not yet clear. The aim of this work was to elucidate the role of p-hydroxybenzoic acid (PHBA), an autotoxin of cucumber (Cucumis sativus L.), in changing soil microbial communities. p-Hydroxybenzoic acid was applied to soil every other day for 10 days in cucumber pot assays. Then, the structures and sizes of bacterial and fungal communities, dehydrogenase activity, and microbial carbon biomass (MCB) were assessed in the rhizosphere soil. Structures and sizes of rhizosphere bacterial and fungal communities were analyzed by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) and real-time PCR, respectively. p-Hydroxybenzoic acid inhibited cucumber seedling growth and stimulated rhizosphere dehydrogenase activity, MBC content, and bacterial and fungal community sizes. Rhizosphere bacterial and fungal communities responded differently to exogenously applied PHBA. The PHBA decreased the Shannon-Wiener index for the rhizosphere bacterial community but increased that for the rhizosphere fungal community. In addition, the response of the rhizosphere fungal community structure to PHBA acid was concentration dependent, but was not for the rhizosphere bacterial community structure. Our results indicate that PHBA plays a significant role in the chemical interactions between cucumber and soil microorganisms and could account for the changes in soil microbial communities in the continuously monocropped cucumber system.

Variation of soil enzyme activities and microbial community structure in peanut monocropping system in subtropical China

The changes in soil microbial community are supposed to be one of key factors for peanut yield decline in long-term continuous monocropping systems. A series of peanut fields, where peanut were continuously monocropped for 3, 6, 10 and 15 years in subtropical China, were selected to investigate the effect of continuous monocropping on peanut yield, soil microbial community structure and enzyme activity. Peanut yield, urease and invertase activities decreased with time, but the activity of polyphenol oxidase decreased in the first several years and then increased. The results of both culture dependent methods and phospholipid fatty acids (PLFA) analysis showed that bacteria (Gram-positive and Gram-negative bacteria) and actinomycetes decreased, while fungal colony-forming units (CFUs) increased with time. Canonical Correspondence Analysis (CCA) showed that with increasing peanut monocropping years, soil microbial structure became more correlative with fungi compositions. The proportion of bacteria in total PLFA decreased from 67.4% to 53.0%, meanwhile the proportion of fungi was increased from 16.9% to 32.8%. Denaturing gradient gel electrophoresis (DGGE) analysis indicated that bacteria diversity decreased and fungi diversity increased with time, and changes in fungi diversity were much greater than those of bacteria. Key words: DGGE, enzyme activities, monocropping, peanut, PLFA, red soil.

Intercropping peanut with traditional Chinese medicinal plants improves soil microcosm environment and peanut production in subtropical China

Many environmental issues affect peanut production in continuous monocropping system. Deterioration of soil microbial communities, especially for decrease in fungal diversity and increase in fungal pathogens, is widely hypothesized as a key factor for decreasing peanut production. In this study, a pot experiment was conducted to investigate the changes in soil microbial communities and peanut yield under the scheme of peanut intercropped with traditional Chinese medicinal plants, including Atractylodes lancea , Dioscorea zingiberebsis , Euphorbia pekinensis , Ophiopogon platyphyllum and Pinellia ternate . The results showed that soil microcosm environment was improved, and the fungal diversity and fungal pathogens such as Fusarium sp. and Verticillium sp. were restrained when peanut intercropped with A. lancea and E. pekinensis . The DGGE analysis of 18S-rRNA from DNA of the total soil communities showed obvious transferring of species of fungi between peanut monocropping and the intercropping systems. Compared with the control, the superoxide dismutase activity of peanut was increased by 43% in A. lancea and 37% in E. pekinensis intercropping systems, along with 37 and 16% yield improvement of peanut, respectively. Based on the result of the pot experiment, A. lancea and E. pekinensis were intercropped with peanuts in a field experiment. A considerable agreement was found between the results obtained from the field and pot experiments. Compared with peanut monocropping system, colony form unit of mould decreased by 31% in A. lancea and 18% in E. pekinensis intercropping treatments, where peanut yields were respectively increased by 39 and 35%. Further research should include integrated PCR-DGGE analysis to determine the transfer of peanut soil-born pathogens and its mechanism, and the optimization of intercropping system and planting density of medicinal plants to obtain the best benefits, and the understanding of the long-term effect of the intercropping systems.

2005~2006 년도 경북지역 담배 병 발생상황

경상북도 북부지역 7개 시 군의 담배재배 농가를 대상으로 병해 발생상황과 농민들의 병해방제법과 관련된 재배방법을 조사하였다. 육묘기와 본밭초기의 담배에서 발생되는 전염성 병해는 극히 미미하였으며, 수확기의 담배에 가장 피해를 주는 병은 감자바이러스 Y에 의한 모자이크병과 세균성마름병(Ralstonia solanacearum)이었다. 담배모자이크바이러스(TMV)에 의한 모자이크병은 저항성 품종의 확대 보급으로 인하여 10년 전에 비하여 크게 감소되었으며, 세균성마름병 발생은 감수성 품종 보급으로 인하여 증가하였다. 30% 이상의 담배 재배 농민들이 농약을 오용하고 있었으며, 같은 수의 농민들이 10년 이상 담배를 연작하고 잘못된 윤작 작물을 선택하였다. Major diseases of tobacco and farmer's control practices were surveyed in the Kyeongbuk province area from 2005 to 2006. Mosaic caused by potato virus Y and bacterial wilt caused by Ralstonia solanacearum were most severe during the harvest season. Compared with the disease occurrence of ten years ago, the damage by tobacco mosaic virus reduced but bacterial wilt increased. These changes in the disease occurrences may probably be due to releasing the resistant tobacco cultivar to the mosaic virus but susceptible to the bacterial wilt pathogen. More than thirty percentage of the farmers have misused fungicides and also have applied the continuous mono-cropping system for more than ten years, and have chosen the incorrect crops for the rotation.

Weather and Management Impact on Crop Yield Variability in Rotations

Crop rotation offers several advantages to improve farmers' systems worldwide. The positive attributes of rotations are usually dependent upon crop choices, cropping sequence, soil fertility management, and weather factors. Of these, weather is most uncontrollable, but its effects can be partially manipulated through management. This study presents information on how weather affected cropping systems in a 12-yr span. The study also illustrates the use of indices of weather (composite) variables to predict yields. The composite variables are three biological windows (BW) and a standardized precipitation index (SPI). Biological windows based on soil temperature and soil moisture indicate the number of days favorable for or detrimental to crop growth. Biological window 2 (temperature > 41°F+moist soil) in combination with May temperature explained more than 80% of the variability in corn (Zea mays) and soybean (Glycine max) yields. August temperature negatively affected corn and soybean yields, especially in continuous monocrops. Preseason 9-mo SPI (September-May) explained up to 50% of the subsequent season's corn yields, and this information could influence crop choice. Overall, yields in rotations were higher than in continuous monocropping systems. Nitrogen fertilization increased cereal yields more in continuous monocropping than in rotations with legumes. Corn and soybean appeared more sensitive to soil moisture and temperature variability (P 0.05). Risk as measured by standard deviation in yields or incomes did not differ significantly among systems.