Upland Crops Research Articles

Impact of clod (aggregate) size on evaporation rate and soil moisture profile during the drying process

AbstractLarge clods (centimetres in size) can be formed by tillage in clayey paddy fields where upland crops are planted. These clods cause early water depletion near the soil surface, which decreases crop germination and emergence rates. Because of the difficulty in reducing clod size, desiccation damage to seeds can be avoided by adjusting the seeding depth based on the clod size‐dependent soil moisture profile. This study aimed to clarify the effect of clod size on (1) the evaporation rate (E) and soil moisture profile and (2) the mobility of soil water during the drying process. Evaporation experiments were conducted in an air‐conditioned greenhouse with natural light using cylindrical columns filled with artificially made clods 3 (L columns) and 1 cm (S columns) in diameter. We measured E, potential evaporation rate (PE), and total soil moisture content (wtot) throughout the experiment and the soil moisture profiles at the end of the experiment. The water diffusivity (Dw) and apparent vapour diffusion coefficient (dvap) were calculated as the mobility of soil water and water vapour, respectively. We found that wtot was lower in the L column than in the S column, although not at the onset of the experiment. At the end of the experiment, the soil moisture content was lower in the L column than in the S column throughout the soil layer. In contrast, E/PE was higher in the L column than in the S column throughout the experiment and even at the same wtot. Regarding mobility, Dw was slightly greater in the L column than in the S column in the soil moisture content range, where vapour movement could be greater than liquid water movement. In addition, the ratio of dvap to the diffusion coefficient of water vapour in soil was higher than unity in both columns and was 2.4–3.2 times higher in the L column than in the S column. In summary, larger clods caused a higher evaporation rate and lower soil moisture content, owing to the increased enhancement of water vapour movement probably induced by wind.

Direct Seeded Rice as Resource Efficient Technology

In Asia, seedlings are typically transplanted into puddled soil to cultivate rice (Oryza sativa L.). Due of the manpower, water, and energy requirements of this manufacturing system, it is becoming less lucrative as these resources become more scarce. Additionally, it impairs the soil's physical qualities, negatively impacts the performance of succeeding upland crops, and increases methane emissions. Different issues, such as a declining water table, a manpower shortage during peak seasons, and worsening soil quality, need the use of alternate establishment techniques to maintain both natural resource and rice yield. Due to its low input requirement, ability to reduce greenhouse gas emissions, and ability to adjust to climatic hazards, the direct seeded rice (DSR) technique has gained a lot of attention and popularity in recent years. Dry seed must be sown into a ready seedbed, while pre-germinated seed must be sown into standing water and puddles of soil. Many farmers have switched from transplanted to DSR culture as a result of the introduction of early maturing cultivars, the application of effective fertiliser management techniques, and increased adoption of integrated weed management strategies. In certain industrialised nations, such the USA, Australia, Japan, China, and Korea, DSR technology is heavily mechanised. By switching from conventional rice to DSR, crop water requirements, soil organic matter turnover, improved nutrient management, carbon sequestration, weed management, greenhouse gas emissions, and crop intensification will all be significantly reduced. The transition from PTR to DSR is hampered by a number of factors, including a high weed infestation, the development of weedy rice, an increase in soil-borne diseases (nematodes), nutritional disorders, poor crop establishment, lodging, the prevalence of blast, brown leaf spot, etc. By addressing these limitations, DSR may show to be a very viable, economically and technically viable substitute for PTR.

Solar radiation utilization of five upland–paddy cropping systems in low-light regions promoted by diffuse radiation of paddy season

Solar radiation affects crop productivity in farmland ecosystems. Global dimming has resulted in decreased incident global radiation over recent decades, with a huge subsequent effect on food security. Attempting to increasing utilization of radiation and production to increase output, especially in multiple cropping systems, is a significant problem in low-light regions. Here, five upland–paddy cropping systems were evaluated in a low-light region during 2016–2017 and 2017–2018: Garlic–rice (GR), wheat–rice (WR), broad bean–rice (BR), rapeseed–rice (RR), and potato–rice (PR). Solar radiation and crop-related indicators were investigated to determine radiation utilization. The results showed that annual global radiation was 4056.97. MJ·m−2 and 3985.43 MJ·m−2 in 2016–2017 and 2017–2018, respectively, 13.69%–26.25% of which was wasted during the fallow season. Furthermore, the seasonal distribution of global radiation was differed to study years. The ratio_dif in paddy season was greater than 75%, whereas in upland season was less than 55%. Additionally, the annual radiation utilization efficiency (RUE) values of the crops investigated in this study were 0.53%–0.80% and RUE during upland season were 0.30%–0.95%, compared to 0.99%–1.35% during paddy season. The ratio_dif during paddy season had a greater contribution to RUE than that of the upland season, whilst the ratio_dif had a positive relationship with RUE. Therefore, in the low light region the high radiation utilization of upland-paddy systems could primarily be attributed to the efficient utilization of diffuse radiation by rice, which had a high radiation interception, net photosynthesis and net assimilation rate. This increase in diffuse radiation will further promote the efficient use of radiation in low-light regions. Furthermore, planting the upland crops with long growth period (garlic) and high planting intensity (wheat and rapeseed) could take advantage of limited global radiation in low-light regions. Our study clarifies RUE magnitude and its causes in upland–paddy cropping systems in low-light regions, while also providing a theoretical reference for grain production prediction and crop RUE improvement within the context of global dimming.

CH4 and N2O Emission and Grain Yield Performance of Three Main Rice-Farming Patterns in Central China

This study focuses on the development of more cropping systems in response to global warming and food security concerns. A two-year field experiment (2017–2018) was conducted to investigate the effects of greenhouse gases (GHGs), soil environmental factors and yield on traditional double-cropping rice (DR), maize rice (MR) and ratooning rice (Rr). The results showed a significant annual effect of temperature and rainfall on GHG emissions under different cropping systems. Annual CH4 emissions under MR and Rr were significantly lower than under DR. Compared to DR, the highest cumulative N2O emissions were observed in MR (14.9 kg·ha−1) with a reduction of 23.7% in Rr. In addition, the upland crops significantly reduced CH4 emissions for late rice, while N2O emissions increased by 20.6%. Compared with DR and Rr, global warming potential (GWP) and greenhouse gas intensity (GHGI) were significantly lower for MR (p < 0.05). Meanwhile, the annual yield of MR (16.40 t·ha−1) was 8.1% and 2.4% higher than that of DR and Rr, respectively. This study further found that soil temperature and NH4+-N content were positively correlated with CH4 and N2O emissions, and soil moisture was positively correlated with N2O emission. Thus, we concluded that MR has the greatest potential to improve crop yield and mitigate GHG emissions in central China.

Effect of replacing synthetic nitrogen fertilizer with animal manure on grain yield and nitrogen use efficiency in China: a meta-analysis.

To reduce reliance on synthetic nitrogen (N) fertilizer and sustain food production, replacing synthetic N fertilizer with animal manure as an effective method is widely used. However, the effects of replacing synthetic N fertilizer with animal manure on crop yield and nitrogen use efficiency (NUE) remain uncertain under varying fertilization management practices, climate conditions, and soil properties. Here, we performed a meta-analysis of wheat (Triticum aestivum L.), maize (Zea mays L.), and rice (Oryza sativa L.) based on 118 published studies conducted in China. Overall, the results indicated that substituting synthetic N fertilizer with manure increased yield by 3.3%-3.9% for the three grain crops and increased NUE by 6.3%-10.0%. Crop yields and NUE did not significantly increase at a low N application rate (≤120 kg ha-1) or high substitution rate (>60%). Yields and NUE values had higher increases for upland crops (wheat and maize) in temperate monsoon climate/temperate continental climate regions with less average annual rainfall (AAR) and lower mean annual temperature (MAT), while rice had higher increases in subtropical monsoon climate regions with more AAR and higher MAT. The effect of manure substitution was better in soil with low organic matter and available phosphorus. Our study shows that the optimal substitution rate was 44% and the total N fertilizer input cannot be less than 161kg ha-1 when substituting synthetic N fertilizer with manure. Moreover, site-specific conditions should also be considered.

Exploring relations between land use changes and agricultural policy implementation in the Mekong Delta of Vietnam: A case of An Giang province

The economy of Vietnam relies mainly on agriculture and the Mekong Delta contributes a crucial part. The region is facing to decline in water resources together with the demand for economic development. Land use changes and policies in agriculture have been implemented in response to natural risks. The study applied a mixed-approach, using both quantitative and qualitative data to explore relations between the status of land use (LU) changes and the implementation of agricultural policies. Multi-temporal Landsat image data including Landsat-5, 7, 8 collected from Google Earth Engine (GEE) database. LU change classification using the Random Forest (RF) method to examine changes in LU in An Giang province from 2000 to 2021. The qualitative data were gathered from individual and group discussions with local authorities, officers and farmers. The results expressed that LU in An Giang province has been changed toward reducing rice areas. Linkages existed between the agricultural policies and the types of LU related to policies of agricultural restructuring. Inappropriate areas for rice have been replaced by upland crops and fruit trees throughout the province. Ecological conditions and specificities of the region contribute to the difference from LU in the province. For agricultural development, value chain and cooperation are necessary to build adaptive and efficient agriculture.

신개발 심층시비장치를 이용한 심층시비의 밭작물 재배 효과

Understanding the Effects of Deep Fertilization on Upland Crop Cultivation and Ammonia Emissions using a Newly Developed Deep Fertilization Device-Ammonia (NH₃),Fertilizer deep placement,Nitrogen,Upland crop,Yield

Responses of arbuscular mycorrhizal fungi to rice–upland crop rotations in an 8‐year paddy ecosystem

AbstractArbuscular mycorrhizal fungi (AMF), which can form symbiotic associations with many terrestrial plants, are critical for crop yields and agroecosystem sustainability. In this study, we assessed the influence of rice–upland crop rotations on soil AMF diversity and composition. We also explored the mechanisms of rice (Oryza sativa L.)–upland crop rotations that affect AMF using trait‐based guild methods. We found that rotations of rice with different plants differentially influenced soil AMF. Rice–wheat (Triticum aestivum L.) (RW) and rice–Chinese milk vetch (Astragalus sinicus L.) (RV) rotations significantly altered the soil AMF composition, with RW and RV significantly increasing and decreasing AMF diversity, respectively, compared with the rice–fallow treatment. In addition, RW and RV affected AMF abundance in intra‐ and extra‐radical portions in different ways. For example, both the RW and RV treatments increased AMF spore density, but decreased AMF colonization rate. Different AMF guilds showed different responses to rice–upland crop rotations. The RW treatment increased the rhizophilic guild by 4.9% and decreased the edaphophilic guild by 27.9%, whereas the RV treatment produced opposite trends. Thus, rice–upland crop rotations changed soil AMF diversity, AMF composition, and trait‐based guilds in different ways, and rice yield was mainly correlated with AMF colonization rate.

Subsurface fertilization boosts crop yields and lowers greenhouse gas emissions: A global meta-analysis

The subsurface application (SA) of nitrogenous fertilizers is a potential solution to mitigate climate change and improve food security. However, the impacts of SA technology on greenhouse gas (GHG) emissions and agronomic yield are usually evaluated separately and their results are inconsistent. To address this gap, we conducted a meta-analysis synthesizing 40 peer-reviewed studies on the effects of SA technology on GHG and ammonia (NH3) emissions, nitrogen uptake (NU), crop yield, and soil residual NO3-N in rice paddies and upland cropping system. Compared to the surface application of N, SA technology significantly increased rice yields by 32 % and crop yield in upland systems by 62 %. The largest SA-induced increases in crop yield were found at low N input rates (<100 kg Nha−1) in rice paddies and medium N input rates (100–200 kg Nha−1) in upland systems, suggesting that soil moisture is a key factor determining the efficiency of SA technology. SA treatments increased yields by more at reduced fertilizer rates (~30 % less N), a shallow depth (<10 cm), and with urea in both cropping systems than at the full (recommended) N rate, a deeper depth (10–20 cm), and with ammonical fertilizer. SA treatments significantly increased NU in rice paddies (34 %) and upland systems (18 %), and NO3-N (40 %) in paddyland; however, NO3-N decreased (28 %) in upland conditions. Ammonia mitigation was greater in paddyland than in upland conditions. SA technology decreased the carbon footprint (CF) in paddyland by 29 % and upland systems by 36 %, and overall by 33 %. Compared with broadcasting, SA significantly reduced CH4 emissions by 16 %, N2O emissions by 30 %, and global warming potential (GWP) by 10 % in paddy cultivation. Given SA increased grain yield and NU while reducing NH3, CF, and GWP, this practice provides dual benefits – mitigating climate change and ensuring food security.

Analysis of Rollover Characteristics of a 12 kW Automatic Onion Transplanter to Reduce Stability Hazards

The rollover tendency of upland farm machinery needs to be carefully considered because upland crop fields are typically irregular, and accidents frequently result in injuries and even death to the operators. In this study, the rollover characteristics of an underdeveloped 12 kW automatic onion transplanter were determined theoretically and evaluated through simulation and validation tests considering the mounting position of the transplanting unit and load conditions. The center of gravity (CG) coordinates for different mass distributions, and static and dynamic rollover angles were calculated theoretically. Simulation and validation tests were conducted to assess the static rollover angle under different mounting positions of the transplanting unit and load conditions of the onion transplanter. The dynamic rollover tendency was evaluated by operating the onion transplanter on different surfaces and at different speeds. According to the physical properties and mass of the onion transplanter, the theoretical rollover angle was 34.5°, and the coordinates of the CG gradually moved back to the rear wheel axle after attaching the transplanting part and under upward riding conditions. The average simulated rollover angle was 43.9°. A turning difference of 4.5° was observed between the right and left sides, where a 3° angle difference occurred due to the load variation. During the dynamic stability test, angle variations of 2~4° and 3~6° were recorded for both high and low driving speeds in the vehicle platform and transplanting unit, respectively. The overturning angles also satisfied the ISO standard. This study provides helpful information for ensuring the safety of upland crop machinery operating under rough and sloped field conditions.

Crop-specific ammonia volatilization rates and key influencing factors in the upland of China - A data synthesis

Ammonia (NH3) is an important alkaline reactive nitrogen (Nr) species which is involved in global nitrogen (N) biogeochemical cycling, but which has negative impacts on the environment and human health. In order to better understand and control the NH3 loss potential in soil-upland crop systems in China, an integrated data analysis including 1302 observations from 236 published articles between 1980 and 2021 was conducted. The typical NH3 volatilization rate (AVR) and the main factors influencing AVR in the major Chinese upland crops (maize, wheat, openfield vegetables and greenhouse vegetables and others) were estimated and analyzed. The mean AVR for maize, wheat, openfield vegetables and greenhouse vegetables were 7.8%, 5.3%, 8.4% and 1.8%. The most important influencing factors were fertilizer placement, meteorological conditions (especially temperature and rainfall) and soil properties (especially SOM). Subsurface N application produced a significantly lower AVR compared to surface application. High N recovery efficiency and N agronomic efficiency were generally associated with low AVRs. In conclusion, high N application rates, inefficient application methods and the use of loss-prone N fertilizer types are the main factors responsible for high AVRs in major Chinese croplands.

Agricultural Water Salinity of Reclaimed Tidelands in Southwestern Coastal Areas of South Korea

Monitoring of the salinity of agricultural soil and water is necessary for sustainable food production in salt-affected reclaimed tidelands (RTLs). Soil salinity has been extensively monitored; however, little attention has been given to water salinity. In this study, agricultural water salinity of five RTLs located in the southwestern coastal area of South Korea was monitored. A total of 215 water samples were collected from estuary lakes and inland streams in Bojeon (BJ), Goheung (GH), Gunnae (GN), Samsan (SS), and Youngsangang (YSG) RTLs in 2018, 2020, and 2022. Water samples were analyzed for electrical conductivity (ECw) and sodium adsorption ratio (SAR) to estimate the suitability of water salinity for agricultural uses based on the FAO guidelines. The ECw (average: 1.6 - 3.6 dS m-1) and SAR (5 - 8) were highly variable being dependent on RTL locations, water type (lake and stream), and sampling year and month. For rice cultivation, ECw of BJ, SS, and YSG RTLs was lower than the threshold ECw (2 dS m-1) for rice growth; whereas ECw of GN (2.1 ± 1.0 dS m-1) and GH (3.6 ± 1.2 dS m-1) RTLs were higher than the threshold ECw. For upland crops cultivation, both ECw and SAR of five RTLs were much higher than the FAO threshold values (ECw < 0.7 dS m-1 and SAR < 3). Therefore, our results suggest that agricultural water salinity of the study RTLs is not suitable for cultivation of upland crop. Therefore, long-term monitoring of water salinity as well as developments of advanced irrigation-drainage are necessary for diversification of agricultural uses of RTLs.Distribution of ECw and SAR of lake and inland stream of five RTLs. On the right side of the panels, FAO guideline for the degree of restriction on the use for irrigation water is depicted.

Vibration Assessment of a 12-kW Self-Propelled Riding-Type Automatic Onion Transplanter for Transplanting Performance and Operator Comfort

Vibration assessment of upland crop machinery under development is essential because high vibrational exposures affect machine efficiency, service life of components, degradation of the working environment, and cause health risks to the operator. It is intensively assessed for automobiles as well as large off-road agricultural vehicles (i.e., tractors). However, it is mostly overlooked in the case of the small or medium riding-type upland utility vehicles. Therefore, the vibration exposures of a 12-kilowatt self-propelled riding-type automatic onion transplanter were measured and evaluated to assess the performance of onion transplantation and the operator’s comfort in this study. Different types of driving surfaces, operating statuses (static and driving), and load conditions were considered to analyze the vibration exposure. The precision of transplantations was evaluated while operating the transplanter on the soil surface with different driving speeds and load conditions. Tri-axial accelerometers and a LabVIEW-coded program were used for data acquisition. The vibrational exposures were evaluated based on ISO standards, and power spectral density (PSD) was estimated to assess the major frequencies. According to the statistical analysis, the daily exposure value (A(8)) and the vibration dose value (VDV) varied from 10 to 15 ms−2 and 20 to 31 ms−1.75, respectively, which exceeded the ISO 2631-1 standards (i.e., A(8): 1.15 ms−2 and VDV: 21 ms−1.75). The calculated health risk factor (RA) was moderate. Moreover, a high weighted acceleration (around 8 ms−2) was observed on the seedling conveyor belt, which might result in missing seedlings during transplanting. The vibration exposures of the developed onion transplanter need to be minimized following the ISO standards, and vibration reduction would also improve the market competitiveness.

First Report of Pseudomonas cichorii Causing Bacterial vein necrosis on Perilla plants [Perilla frutescens (L.) Britton.] in South Korea.

Perilla (Perilla frutescens L.) is the second most important upland crop and the third largest edible oil crop in Korea (Shin and Kim 1994). During a disease survey in Busan, Korea in September 2021, symptoms of vein necrosis were observed in perilla plants, with incidences of approximately 30% and 50% in two fields. Symptoms of spots on the perilla appeared as leaf dryness and spots with water-soaked blotches largely concentrated on the mid-veins of leaves. The lesions were initiated with water-soaked spots on the leaf or stem and gradually turned black or brown. Necrosis was also observed in the stems. A bacterium was isolated on Luria-Bertani (LB) agar from diseased leaf tissues that were surface-disinfected with 70% ethyl alcohol for 3-5 min and then washed with sterile water three times. Three pieces of sterilized leaf tissue (size: 0.5 × 0.5 cm) were mixed with 500 µL sterile water for 30 min, and then the suspension was serially diluted and spread on LB agar. Subsequently, isolates were cultivated on LB agar and King's Medium B agar (KMB) (Schaad et al. 2001), and they were predominantly cream-colored and circular bacterial colonies with undulated margins. The bacterial colonies on KMB displayed fluorescence under 365 nm UV light. The isolates were analyzed with the GEN III MicroPlate (Biolog, Hayward, CA, USA), and all isolates were identified as Pseudomonas cichorii, a devastating plant bacterium that damages a wide range of host plants worldwide, including in South Korea (Hikichi et al. 2013; Ramkumar et al. 2015). To identify the species of the bacterial pathogen, genomic DNA of four isolates (BS4922, BS4167, BS4345, and BS4560) was extracted, and the 16S rRNA gene and hrcRST gene were amplified with universal primers, 27F/1492R and Hcr1/Hcr2, and sequencing was then done (Patel et al. 2019). In the BLAST analysis, the 16S rRNA sequences (GenBank OM060656, OM275434, OM275435, OM275436) showed a 100% and 99% similarity to P. cichorii strains MAFF 302698 (AB724286) and P. cichorii strain Pc-Gd-4 (KU923373), respectively. Further, hrcRST gene sequences (GenBank OM143596, OM268864, OM268865, and OM268866) showed high similarity (>99%) with P. cichorii strain P16-51 (MG518230). A pathogenicity test of the four isolates was performed on 3 - 4 weeks old perilla plants by creating wounds with a needle on the lower leaves and stems, and then the plants were inoculated by spraying inoculum (108 CFU/ml). The plants that served as the negative control were wounded and sprayed with unsterilized water. The inoculated perilla plants were placed in a greenhouse at 28 ± 2oC , 80-85% relative humidity, and a natural photoperiod. The inoculation site began to show symptoms of water-soaked brown lesions. Disease symptoms such as leaf dryness, water-soaked blotches on the mid-vein of leaves, and necrosis on plant stems were observed in the inoculated plants 7-10 days after inoculation, whereas the plants of the negative control group did not show any symptoms. The bacteria were re-isolated from the diseased tissues of the plants, and DNA sequence analysis identified them as P. cichorii. Additionally, all isolates induced hypersensitivity reactions in tobacco and tomato leaves within 24 h after inoculation. To our knowledge, this is the first report of P. cichorii infecting perilla in South Korea. The findings in this study will provide the basic information for the development of diagnostic tools and management measures against P. cichorii in perilla.

Assessing the impact of food trade centric on land, water, and food security in South Korea

The observed and predicted changes in climate, as well as the growth in urban population, are creating severe stress on existing water resources in South Korea. By the importation of agricultural products from more water-rich countries through the virtual water concept, a country could save local water resources for other important uses. However, these imports from other countries could lead to certain vulnerabilities in the importing country derived from climate change. Therefore, through the application of the virtual water concept and the climate vulnerability index ((CVI) - measure of a country's vulnerability to indirect climate impacts), this study assessed the implication of virtual water imports and climate change through food trade, on the water, land and food security status of South Korea over the period of 2000–2017. The results showed that significant amounts of national water and land was saved through the importation of major upland crops. Virtual water imports increased significantly over time, rising from 16.2 Bm3 in 2000 to 16.5, 17.4, and 20.7 Bm3 in 2005, 2011, and 2017 respectively, with the USA, China, Australia, Brazil and Canada being the major exporters to South Korea. The study also revealed high CVI values for the oils and grains category of imported food, implying the high vulnerability of South Korea to climate change effects resulting from the import of these crops. The quantitative impacts and structural changes in virtual water trade, as well as the link between climate change, food security, international trade, and domestic water consumption could be evaluated for the sustainable management and allocation of resources. This study successfully identified and quantified the status of food trade and its environmental implications in the study area, providing insight into a better allocation of locally available resources.

The effect of upland crop planting on field N2O emission from rice-growing seasons: A case study comparing rice-wheat and rice-rapeseed rotations

Paddy fields, especially under flooded rice-upland crop rotation modes, undergo tremendous changes in soil redox conditions. The effects of different upland crop plantations on field N2O emissions from the rice-planting period and the underlying mechanisms are scarce. In this study, two types of flooded rice-upland cropping rotation modes, namely, rice-rapeseed rotation (RR) and rice-wheat rotation (RW), were selected to investigate the effects of different upland crop plantations on field N2O emissions during the rice-growing period, in central China. To confirm the effect of upland crop plantations on soil variables and associated functional genes, conventional rice planting (RR-CP and RW-CP) with a part of the non-rice area (RR-NP and RW-NP) during the rice season was implemented. Results revealed that seasonal N2O emissions from RR-NP and RW-NP treatments were 1.83 ± 0.18 and 1.43 ± 0.25, and 1.41 ± 0.09 and 0.88 ± 0.08 kg N ha−1, respectively, during two consecutive rice-plantation seasons, which were significantly higher than those from RR-CP treatment (1.38 ± 0.16 and 0.91 ± 0.15 kg N ha−1) and RW-CP treatment (0.95 ± 0.08 and 0.50 ± 0.10 kg N ha−1). Higher N2O emissions from RR rotation than from RW rotation, regardless of rice planting, indicated that upland cultivation affected soil N2O efflux. For rice planting treatments, strong positive relationships between N2O fluxes and soil-dissolved organic carbon (DOC), ammonium (NH4+), nitrate (NO3-), and functional genes (nirS, nirK, and nosZ genes) were observed, implying that soil available C and N, and related functional genes are key regulatory factors controlling N2O emissions. Compared with the RW-CP treatment, the higher abundance of the nirK gene and lower nosZ/(nirS + nirK) ratio from the RR-CP treatment may facilitate greater N2O production, while reducing conversion of N2O to N2, resulting in increased N2O emissions. Furthermore, structural equation model (SEM) showed that field flood depth (FD), soil available C and N, and the abundance of nirS gene, together, displayed more than 70 % impact effect on N2O emission for RR-CP treatment, while, FD, soil available N, and nirS and nirK genes, together, displayed more than 60 % impact effect on N2O emission for RW-CP treatment. Our results suggest that suitable upland crop rice cultivation could be beneficial for mitigating soil N2O emissions.

Plant hydraulic resistance controls transpiration of soybean in rotational paddy fields under humid climates

Efficient irrigation and drainage management are highly required for increasing crop productivity in paddy rice and upland crop rotation. However, conventional management does not sufficiently consider the water status of the plants and soil in the root zone. The aim of this study was to evaluate whether the hydraulic resistance of soil (Rs) or plant (Rp) principally controlled transpiration in rotational paddy fields (RPFs) located in humid regions. To achieve this, we conducted field measurements of soil water conditions, evapotranspiration rate, and leaf water potential in RPFs cropped with soybean after the flowering stage and calculated Rs and Rp based on the theory of root water uptake. After the flowering stage, the soil was sometimes saturated owing to intermittent precipitation, and thus Rs was maintained at a low value. By contrast, Rp gradually increased over time and ranged between 5.1 × 108 and 10.3 × 108 s, which was one to three orders of magnitude higher than Rs. The ratio of the actual to the potential transpiration rate decreased throughout the investigation period and hardly reached 1.0, even though the soil was sufficiently wet. These results indicate that Rp, which probably increases with continuous soil saturation, controls crop transpiration in RPFs under humid climates. Our results suggest that drainage systems are essential in RPFs to avoid a change in Rp and improve crop productivity.

Reducing greenhouse gas emission by alternation of the upland crop rotation in the Mekong Delta, Vietnam

Agricultural production is one of the main sources of anthropogenic greenhouse gas (GHG) emissions, contributing 50% and 60% of CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O emissions, respectively. This study evaluated the rice yield and components, the CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O emissions and the global warming potential between the triple rice (R-R-R) and sesame-rice rotation (S-R-R) systems in Can Tho city, Vietnam. The experiments were conducted in three cropping seasons: spring-summer 2016, summer-autumn 2016, and winter-spring 2016–2017. The results showed that there was no significant difference in the yield components and grain yield between the triple rice and sesame-rice rotation systems. The application of a sesame rotation in rice-based system could reduce the CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O emission by 30.5% and 18.7%, respectively. The global warming potential in the S-R-R rotation was 9 860 kg CO&lt;sub&gt;2e&lt;/sub&gt;/ha, significantly lower than the R-R-R rotation (12 410 kg CO&lt;sub&gt;2e&lt;/sub&gt;/ha) by 20.6%. These results show that the S-R-R rotation has the potential to mitigate the GHG emissions, especially CH&lt;sub&gt;4&lt;/sub&gt;, which contributes a large amount of emissions in the rice cultivation.

Diversity and function of soil microorganisms in response to paddy–upland rotation system in sustainable restoration of saline-sodic soils

Context Rapid desalination by planting rice in saline soil consumes large amounts of water, which is not environmentally friendly. Aims Herein, we propose rapid desalination by planting rice, then shifting to cultivating upland plants to attain substantial resource-saving and higher yield simultaneously with restoration of saline-sodic soil. Methods Field experiments were run for two consecutive years with five treatments: unreclaimed wasteland (WL) as control, rice cultivation followed by fallow (RF), rice–rice continuous cropping (RR), rice–ryegrass rotation (RG), and rice–sorghum rotation (RS). Physicochemical properties, including pH, electrical conductivity, and exchangeable sodium percentage were determined, and 16S rRNA sequences were used to evaluate soil microbial composition and stability. Key results The soil total organic carbon, total nitrogen, available phosphorus, and biomass in RR, RG, and RS treatments were all higher than RF and control. Notably, RR, RG, and RS increased the soil microbial biomass carbon and nitrogen, and significantly reshaped the soil communities of bacteria, fungi, and archaea relative to RF and WL. Conclusions Despite the lower efficiency of RG and RS in ameliorating saline-sodic soil, there were dramatic savings in irrigation water, and the improvements in microbial diversity and functionalities indicated that the paddy–upland crop rotation system had substantial influence on sustainability of soil quality. Implications Providing a balance between salt desalination performance with irrigation water input and yield, the paddy–upland rotation system is a robust, replicable, and environmentally friendly practice in saline-sodic soil remediation.

Growth and Productivity of Cauliflower in Aonla Based Multistoried Agroforestry System

Fruit tree vegetable-based agroforestry systems (FVAS) are being introduced in highland cropping systems of Bangladesh. This combined production system is applicable against changing climate, ensuring nutritional requirements along with food security, ecological balance, and economic profitability. The present study explored the performance of cauliflower as lower story crop in aonla based multistoried agroforestry system. The experiment was laid out in randomized complete block design (RCBD) with four replication. The treatments were T1= Aonla + carambola + lemon + dragon fruit + cauliflower, T2= Aonla + dragon fruit + cauliflower, T3= Dragon fruit + cauliflower, T4= Cauliflower in the open field (Control). Among different combinations of agroforestry systems, the highest curd yield of cauliflower (15 t ha-1) was recorded under dragon fruit-based system (T3) whereas most of the morphological parameters were maximum in the aonla + carambola + lemon + dragon fruit-based system (T1). The highest benefit–cost ratio (2.95) was noted in aonla+dragon+cauliflower-based system (T2) followed by dragon fruit based system (T3), while the highest land equivalent ratio (3.78) was calculated in the aonla + carambola + lemon + dragon fruit-based system (T1). This study revealed that, aonla + dragon + cauliflower based agroforestry system showed relatively higher economic returns and maximum land use efficiency in the upland cropping system.