Effect of Long-term Cropping Systems on Soil Hydrophobicity of a Clay Loam Soil Under Dryland Conditions in Southern Alberta

The objective was to quantify the effect of crop rotations, crop type, life cycle, nitrogen fertilizer, manure application, and fallow on soil hydrophobicity (SH). The SH was measured for a long-term (16 yr) dryland field experiment on a Dark Brown clay loam soil in southern Alberta, Canada. Mean SH was significantly (P ≤ 0.05) greater in rotations with grass, perennial crops, manure application, and continuous cropping; whereas cereal-legume rotations and N fertilizer effects were undetectable. A strong, positive correlation occurred between SH and soil organic carbon concentration (r=0.73). Soil water repellency should be measured on these plots using water-based methods.

Land-use intensification differentially affects bacterial, fungal and protist communities and decreases microbiome network complexity

Background Soil microbial communities are major drivers of cycling of soil nutrients that sustain plant growth and productivity. Yet, a holistic understanding of the impact of land-use intensification on the soil microbiome is still poorly understood. Here, we used a field experiment to investigate the long-term consequences of changes in land-use intensity based on cropping frequency (continuous cropping, alternating cropping with a temporary grassland, perennial grassland) on bacterial, protist and fungal communities as well as on their co-occurrence networks. Results We showed that land use has a major impact on the structure and composition of bacterial, protist and fungal communities. Grassland and arable cropping differed markedly with many taxa differentiating between both land use types. The smallest differences in the microbiome were observed between temporary grassland and continuous cropping, which suggests lasting effects of the cropping system preceding the temporary grasslands. Land-use intensity also affected the bacterial co-occurrence networks with increased complexity in the perennial grassland comparing to the other land-use systems. Similarly, co-occurrence networks within microbial groups showed a higher connectivity in the perennial grasslands. Protists, particularly Rhizaria, dominated in soil microbial associations, as they showed a higher number of connections than bacteria and fungi in all land uses. Conclusions Our findings provide evidence of legacy effects of prior land use on the composition of the soil microbiome. Whatever the land use, network analyses highlighted the importance of protists as a key element of the soil microbiome that should be considered in future work. Altogether, this work provides a holistic perspective of the differential responses of various microbial groups and of their associations to agricultural intensification.

A Polysaccharide of Ganoderma lucidum Enhances Antifungal Activity of Chemical Fungicides against Soil-Borne Diseases of Wheat and Maize by Induced Resistance

Ganoderma lucidum polysaccharide (GLP), which is the primary active ingredient in G. lucidum, has been widely used in functional food and clinical medicine. However, it is rarely reported in the prevention and control of plant diseases. In this study, we found that the GLP can increase the germination rates and seedling heights of maize and wheat. We also found that the combination of GLP and chemical fungicides as a seed coating chemical compound has a control effect of more than 75% on the primary soil-borne diseases of the wheat and maize growing areas in both greenhouse and field trials. Furthermore, the combination of GLP and chemical fungicides prolongs the lasting period and reduces the application dosage of the chemical fungicides by half. In addition, GLP seed dressing could increase the resistance-related gene expression of the TPS and WRKY53 in maize and WMS533, NbPR1a, and RS33 in wheat. The combination of GLP and low-dose chemical fungicides proved to be an effective way to effectively prevent wheat sharp eyespot, root rot, and maize stalk rot in the wheat and maize continuous cropping areas in the North China Plain and to reduce pesticide use and increase crop yield.

Assessing Impacts of Different Land Use Types on Soil Properties ın Asa and Moro Local Government Area, Kwara State, Nigeria

Successful agriculture requires the sustainable use of soil resource, because soil can easily lose its quality and quantity within a short period of time. Agricultural practices, therefore, needed basic knowledge of sustainable use of land. This research was conducted in Asa and Moro Local Government Areas of Kwara State to assess the impacts of different land use types on soil properties in the study area. Six villages noted for farming were randomly visited and in each village, three farms planted each with maize-cassava intercrop, cashew plantation and natural forest were sampled at 0-20 cm depth for laboratory analysis of particle size, pH, carbon, nitrogen, phosphorus, exchangeable cations and extractable micronutrients. The bulk density at 0-5 cm, 5-10 cm and 10-15 cm depths were determined. Soil properties were analysed using descriptive statistics. The soil texture was sandy loam with soil pH ranging from slightly acid to acid (6.4 to 5.1). Irrespective of the local government areas and land use, organic carbon (1.83 g kg-1), Sodium (0.12 cmol kg-1), Nitrogen (0.12 g kg-1) and Phosphorus (6.15 mg kg-1) were low while Fe (134.80 mg kg-1), Mn (122.80 mg kg-1) and Zn (19.22 mg kg-1) were high. Across the local government areas, Potassium and Magnesium varied from medium to high while Calcium and Copper were low to medium. The bulk density range was medium to high (1.36 to 1.57 g cm-3) for cashew plantations and maize-cassava intercrop while it was medium (1.40 to 1.47 g cm-3) for natural forest. In conclusion, most of the cultivated soils were low in fertility, with low carbon stocks which is assumed to be due to emission losses arising from continuous cropping. The carbon sequestration status of land uses in the study area was very low. Management practices like composting, green manuring, use of organic fertilizer and residue retention is recommended.

Continuous Cropping Changes the Composition and Diversity of Bacterial Communities: A Meta-Analysis in Nine Different Fields with Different Plant Cultivation

Chinese goldthread (Coptis chinensis Franch.) represents one of the most important medicinal plants with diverse medicinal applications, but it easily suffers from continuous cropping obstacles in the plantation. In this study, we have selected eight different continuously cropped fields with C. chinensis and fallow field, providing detailed information regarding the diversity and composition of the rhizospheric bacterial communities. We have found a significant difference between fallow field (LH) and other continuously cropped fields in soil pH; the total content of nitrogen, phosphorus, and potassium; and soil enzyme activities. The results indicate that continuous cropping had a significant effect on soil physicochemical properties and enzyme activities under different plant cultivations. The relative abundance of bacterial phyla was significantly altered among the fields; for example, proteobacteria and Actinobacteria were observed to be higher in continuous cropping of maize (HY6) and lower in sweet potato continuous cropping (HH). Alpha diversity analysis showed that different plants with different years of continuous cropping could change the diversity of bacterial communities, among which the effect of maize and Polygonum multiflorum continuous cropping were most significant. Principle coordinate analysis (PCoA) showed that continuously cropped C. chinensis (LZ) and cabbage continuously cropped for 2 years (HS) were slightly clustered together and separated from LH and others. The results showed that the similarity of the bacterial community in the same crop rotation was higher, which further indicated that the bacterial community structure was significantly altered by the continuous cropping system and plant species. Our study provides a foundation for future agricultural research to improve microbial activity and increase crops/cash-crops productivity under a continuous cropping system and mitigate continuous cropping obstacles.

Decoupling of P from C, N, and K Elements in Cucumber Leaves Caused by Nutrient Imbalance under a Greenhouse Continuous Cropping System

There is insufficient information regarding the stoichiometric variation and coupling status of carbon (C), nitrogen (N), phosphorus (P), and potassium (K) in the leaves of nutrient-enriched greenhouse agroecosystems with increasing planting time. Therefore, we assessed the variation in elemental stoichiometry ratios in soil and cucumber (Cucumis sativus L.) leaves, and the coupling status of elemental utilization in the leaves under continuous cropping systems using natural (only soil; i.e., control soil, CO) and artificial (soil + straw + chicken + urea; i.e., straw mixture soil, ST) soil via monitoring studies for 11 years in a solar greenhouse. Soil organic C, total N, and total P concentrations increased by 63.4%, 72.7%, and 144.3% in the CO, respectively, after 11 years of cultivation (compared to the first year), and by 18.1%, 24.3%, and 117.7% in the ST under continuous cropping conditions, respectively. Total K concentrations remained unchanged in both soils. Moreover, the availability of these soil elements increased to different degrees in both soils after 11 years of planting. Additionally, the leaf P concentration increased by 9.8% in the CO, while leaf N and K concentrations did not change, suggesting decoupling of P utilization from that of N and K in leaves under a continuous cropping system. These findings suggest that imbalanced soil nutrients under continuous cropping conditions results in decoupling of P from N and K in the utilization of leaf nutrients.

Effects of tillage methods on soil physical properties and crop yield in arid area of northwest China

Effects of no-tillage, deep tillage and tillage on soil physical properties and maize yield in Weibei dryland were studied through field experiments from 2008 to 2010. The results showed that the soil bulk density was the highest under no-tillage treatment. The maximum field water holding capacity and saturated water content were both the highest under deep-plowing treatment, which were 29.66 and 31.31%, respectively. Under the condition of balanced fertilization, during the growth period of maize, the average soil water storage of no-tillage and deep-plowing treatment was 44.2 and 34.6 mm higher than that of ploughing treatment. The yield, water use efficiency and net income of deep-plowing treatment with balanced fertilization were the highest among three combinations of tillage. It can be seen that the treatment of deep loosening with balanced fertilization is the best combination of tillage and fertilization in continuous cropping corn field in Weibei Arid Plateau. Bangladesh J. Bot. 50(3): 819-829, 2021 (September) Special

Continuous monocropping highly affect the composition and diversity of microbial communities in peanut (Arachis hypogaea L.)

Continuous cropping systems are the leading cause of decreased soil biological environments in terms of unstable microbial population and diversity index. Nonetheless, their responses to consecutive peanut monocropping cycles have not been thoroughly investigated. In this study, the structure and abundance of microbial communities were characterized using pyrosequencing-based approach in peanut monocropping cycles for three consecutive years. The results showed that continuous peanut cultivation led to a substantial decrease in soil microbial abundance and diversity from initial cropping cycle (T1) to later cropping cycle (T3). Peanut rhizosphere soil had Actinobacteria, Protobacteria, and Gemmatimonadetes as the major bacterial phyla. Ascomycota, Basidiomycota were the major fungal phylum, while Crenarchaeota and Euryarchaeota were the most dominant phyla of archaea. Several bacterial, fungal and archaeal taxa were significantly changed in abundance under continuous peanut cultivation. Bacterial orders, Actinomycetales, Rhodospirillales and Sphingomonadales showed decreasing trends from T1>T2>T3. While, pathogenic fungi Phoma was increased and beneficial fungal taxa Glomeraceae decreased under continuous monocropping. Moreover, Archaeal order Nitrososphaerales observed less abundant in first two cycles (T1&T2), however, it increased in third cycle (T3), whereas, Thermoplasmata exhibit decreased trends throughout consecutive monocropping. Taken together, we have shown the taxonomic profiles of peanut rhizosphere communities that were affected by continuous peanut monocropping. The results obtained from this study pave ways towards a better understanding of the peanut rhizosphere soil microbial communities in response to continuous cropping cycles, which could be used as bioindicator to monitor soil quality, plant health and land management practices.

Steady agronomic and genetic interventions are essential for sustaining productivity in intensive rice cropping

Intensive systems with two or three rice (Oryza sativa L.) crops per year account for about 50% of the harvested area for irrigated rice in Asia. Any reduction in productivity or sustainability of these systems has serious implications for global food security. Rice yield trends in the world’s longest-running long-term continuous cropping experiment (LTCCE) were evaluated to investigate consequences of intensive cropping and to draw lessons for sustaining production in Asia. Annual production was sustained at a steady level over the 50-y period in the LTCCE through continuous adjustment of management practices and regular cultivar replacement. Within each of the three annual cropping seasons (dry, early wet, and late wet), yield decline was observed during the first phase, from 1968 to 1990. Agronomic improvements in 1991 to 1995 helped to reverse this yield decline, but yield increases did not continue thereafter from 1996 to 2017. Regular genetic and agronomic improvements were sufficient to maintain yields at steady levels in dry and early wet seasons despite a reduction in the yield potential due to changing climate. Yield declines resumed in the late wet season. Slower growth in genetic gain after the first 20 y was associated with slower breeding cycle advancement as indicated by pedigree depth. Our findings demonstrate that through adjustment of management practices and regular cultivar replacement, it is possible to sustain a high level of annual production in irrigated systems under a changing climate. However, the system was unable to achieve further increases in yield required to keep pace with the growing global rice demand.