The rice dry direct-seeding planting mode is a typical shallow sowing operation, and the traditional compacting mechanism with only longitudinal profiling ability is difficult to ensure the seedbed ...uniformity, resulting in the seedling emergence rate always lower than 80%. This study innovatively proposed a novel bidirectional-micro-profiling compacting device (BMPCD). In this study, the coupled DEM-MFBD simulation technique was utilised to find that the core design parameters k (elasticity coefficient of the reset spring) and t (thickness of the elastic sheet) of the BMPCD would significantly affect the seedbed uniformity by changing the resistance value Fr during the profiling process (P ≤ 0.01). The simulation results showed that when k was taken as 7.8 N mm−1 and t was taken as 1.6 mm, the seedbed uniformity could be most greatly improved. The field experiments showed that compared with the bidirectional profiling compacting device (BPCD) and longitudinal profiling compacting device (LPCD), BMPCD could reduce the coefficient of variation of soil firmness (CVSF) by 33.1% and 40.1%, and the coefficient of variation of sowing depth (CVSD) by 37.1% and 51.8%, respectively, and then improve the seedling emergence rate of dry direct-seeded rice by 5.8% and 12.2%. This indicated that bidirectional and micro-profiling compaction technology could tackle the problem of low seedling emergence rate in rice dry direct-seeding. Meanwhile, the results of the DEM-MFBD coupling simulation were not significantly different from the test results of the field experiments (P > 0.05), indicating that it could be used as an efficient and accurate new method to study the dynamic characteristics between the soil and machinery.
•The BMPCD can improve the compacting stability of rice dry direct-seeding.•The DEM-MFBD coupling simulation can realise high precision optimisation of BMPCD.•The BMPCD can increase the seedling emergence rate of dry direct-seeded rice by 12.2%.
Development of water‐saving techniques for irrigated lowland rice production system is a requirement in the context of increasing irrigation water scarcity. A pot experiment was conducted to evaluate ...the performance of selected lowland Thai rice varieties grown under different cultivation methods subjected to alternate wetting and drying (AWD) irrigation. Treatments consisted of three varieties (Pathumthani 1, RD57 and RD41), three cultivation methods (dry direct seeding DDS, wet direct seeding WDS and transplanting TP) and four AWD irrigation levels (re‐watered when soil water potential reached at 0, −5, −15 and −30 kPa). DDS resulted in higher grain yield at −5 and −15 kPa (74 and 68 g/pot, respectively) with a respective reduction of 15 and 34% under WDS and TP at −5 kPa, and 15 and 28% at −15 kPa. The highest water productivity was recorded at −30 kPa under DDS, which was reduced by 17–61% for other soil water potentials irrespective of varieties; however, grain yield was also reduced by 12–19% at −30 kPa. All varieties responded similarly to water‐saving techniques (direct seeding and different levels of AWD) with non‐significant differences in grain yield and water productivity; therefore, could be recommended to grow these varieties using water‐saving techniques. The optimum threshold level of AWD could be −15 kPa for its high grain yield and water productivity.
The performance of selected lowland Thai rice varieties grown under different cultivation methods subjected to alternate wetting and drying (AWD) irrigation was evaluated. Dry direct seeding (DDS) resulted in higher grain yield at −5 and −15 kPa. The highest water productivity was recorded at −30 kPa under DDS. The optimum threshold level of AWD could be −15 kPa for its high grain yield and water productivity.
•A ∼ 2 °C temperature increase advances oak seedling emergence.•Increased temperatures reduced summer seedling growth and survival.•Larger seeds of Quercus faginea emerged earlier.•Early emerged ...seedlings were most likely to survive, irrespective of temperature.•Restoration projects should consider seed size to promote success under climate change.
Climate change constitutes a major threat to global biodiversity and to the success of natural and assisted tree regeneration. Oaks are among the most emblematic tree species in the Northern Hemisphere, so it is crucial to understand the impact of changing climate on seedling recruitment and early development. In this study, we investigated the effect of air warming on the early development of one deciduous species – Quercus faginea – and one evergreen species – Quercus ilex subsp. ballota. Acorns of both species were seeded in an alluvial valley in southern Spain and subjected to an air warming treatment with Open-Top Chambers (OTC), which increased air temperature by 2 °C. We monitored seedling emergence, growth, chlorophyll concentration, and mortality in the first growing season. The simulated climate change treatment accelerated plant emergence in early spring, reduced spring shoot growth, and increased mortality from ∼ 23 % in control plots to ∼ 40 % inside OTCs. Although Q. ilex and Q. faginea are sympatric species, Q. faginea showed lower performance under simulated climate change in terms of growth. In addition, acorn fresh weight was positively related with the probability and speed of emergence (only for Q. faginea), seedling size, and relative chlorophyll content, and plants that emerged earlier had a greater likelihood of surviving. In short, larger acorns partly counter-balanced the negative impact of temperature increase on plants. This study highlights the importance of understanding plant response to climate change both to forecast potential changes in species composition and to choose adequate species and traits such as acorn size in restoration projects.
•Shelterwood seed cutting combined with soil scarification can help to diversify tree regeneration.•A limited seed source and excessive deer browsing can hinder management efforts.•Limitation of seed ...can be a critical impediment for diversity of natural regeneration.•Integrated approaches may be necessary for increasing tree regeneration diversity.
Silviculture methods such as clearcutting, shelterwood seed cutting, and selection system are used to manipulate the canopy and regenerate new cohorts in hardwood stands. Additionally, site preparation can be utilized to alter seedbed conditions with the aim to promote changes in species composition. However, limited seed availability and increased ungulate browsing may limit successful natural regeneration in some areas. Our objective was to investigate the influence of regeneration method, site preparation, deer exclusion, and direct seeding on the regeneration of a managed northern hardwood forest. Utilizing a randomized split-plot design with three splitting levels, we examined the effects of four different regeneration methods, two site preparation treatments, seed limitation and deer browsing on composition, compositional heterogeneity, and richness of regenerating tree species. We observed significant differences in the resulting species composition related to the regeneration and site preparation methods. Shelterwood seed cutting implemented with 60% and 30% residual canopy cover, along with scarification, increased species richness and species compositional heterogeneity. However, the combination of deer exclusion and direct seeding resulted in the highest species richness across all treatment combinations. Deer exclusion alone did not enhance richness or compositional heterogeneity, highlighting the impeding effect of limited seed availability. We found that direct seeding successfully altered species composition and increased species richness. Our results suggest that while the regeneration and site preparation methods can benefit natural tree regeneration, approaches that also address both seed limitations and deer browsing will be necessary to increase the tree species diversity in some cases.
•Significantly higher ratoon season yields were observed in hybrid rice cultivars than inbred ones in DSR-RR.•Higher regeneration rate contributed to the higher ratoon season yield in hybrid rice ...cultivars than inbred ones.•Higher regeneration rate in hybrid rice cultivars over inbred ones was attributed to the higher dry weight per stem after harvesting of the first crop.•Hybrid rice cultivars may be more suitable for DSR-RR.
Ratoon rice system is one method to increase food production in areas where the annual accumulation of temperature and light resources are considerably more than that required for single‐cropping rice but not enough for double-season rice. Direct seeding rice-ratoon rice (DSR-RR) is an alternative rice planting system to traditional transplanted rice-ratoon rice (TTR-RR) in central China, requiring less labor. Hybrid rice has higher yield potential than inbred rice under TTR-RR. However, little attention has been paid to the differences in growth and yield performance of inbred and hybrid rice cultivars in DSR-RR. Field experiments were conducted to evaluate the performance of widely grown inbred and hybrid rice cultivars in central China in 2016 and 2017. Significantly higher ratoon season yields were observed in hybrid rice cultivars than inbred rice cultivars. The ratoon season yield that was achieved was 4.19 t ha−1 in inbred rice cultivar and 5.71 t ha−1 in hybrid rice cultivar in 2016. Similarly, the ratoon season yields ranged from 2.39 to 3.99 t ha−1 in inbred rice cultivars and from 3.84 to 4.90 t ha−1 for hybrid rice cultivars in 2017. Significantly higher regeneration rates contributed to the higher ratoon season yield in hybrid rice cultivars than inbred ones. Further research indicated that higher regeneration rate was associated with higher dry weight per stem after harvesting of the first crop in hybrid rice cultivars as compared with inbred ones. Furthermore, higher annual grain yields were observed in hybrid than in inbred rice cultivars in both years, indicating that hybrid rice cultivars may be more suitable for DSR-RR. To achieve high ratoon season and annual yields in DSR-RR in central China, cultivars should be selected with comprehensive considerations of high regeneration rates and lodging resistance.
► Dry-seeded rice can be sown after land preparation or under zero-till conditions. ► Weeds are the major constraint to the production of dry-seeded rice. ► The efficacy of herbicides was lower in ...the zero-till system than in the conventional tillage system. ► Grain yield in the herbicide-treated and weed-free plots was similar between the tillage systems. ► Grain yield in the zero-till-weedy plots was lower than in the conventional tillage-weedy plots.
Farmers in many Asian countries are moving from puddled-transplanted rice to dry-seeded rice systems. Dry-seeded rice can be sown after land preparation or under zero-till conditions. Weeds, however, are the major constraint to the production of dry-seeded rice. A study was conducted during the wet season of 2011 and dry season of 2012 at the farm of the International Rice Research Institute to evaluate the effect of tillage systems (zero-till and conventional tillage) and herbicides on weed emergence, weed growth, and grain yield in dry-seeded rice systems. In the zero-till system, the densities of Digitaria ciliaris, Eleusine indica, Eclipta prostrata, and Ludwigia octovalvis increased many-fold from the first season to the second. The efficacy of herbicides (oxadiazon followed by fenoxaprop+ethoxysulfuron and oxadiazon followed by penoxsulam+cyhalofop) was lower in the zero-till system than in the conventional tillage system. Grain yield in the herbicide-treated and weed-free plots was similar between the tillage systems and this response was consistent during both the seasons. However, grain yield in the zero-till-control (one hand-weeded) plots was lower (0.9–1.5tha−1) than in the conventional tillage-control plots. The information gained from this study suggests that yields in zero-till systems similar to those in conventional-tilled systems can be achieved if weeds are effectively controlled. In the absence of effective weed control, zero-till systems may result in poor grain yield.
Rice (Oryza sativa L.), a staple food for more than half of the world population, is commonly grown by transplanting seedlings into puddled soil (wet tillage) in Asia. This production system is ...labor-, water-, and energy-intensive and is becoming less profitable as these resources are becoming increasingly scarce. It also deteriorates the physical properties of soil, adversely affects the performance of succeeding upland crops, and contributes to methane emissions. These factors demand a major shift from puddled transplanting to direct seeding of rice (DSR) in irrigated rice ecosystems. Direct seeding (especially wet seeding) is widely adopted in some and is spreading to other Asian countries. However, combining dry seeding (Dry-DSR) with zero/reduced tillage (e.g., conservation agriculture (CA)) is gaining momentum as a pathway to address rising water and labor scarcity, and to enhance system sustainability. Published studies show various benefits from direct seeding compared with puddled transplanting, which typically include (1) similar yields; (2) savings in irrigation water, labor, and production costs; (3) higher net economic returns; and (4) a reduction in methane emissions. Despite these benefits, the yields have been variable in some regions, especially with dry seeding combined with reduced/zero tillage due to (1) uneven and poor crop stand, (2) poor weed control, (3) higher spikelet sterility, (4) crop lodging, and (5) poor knowledge of water and nutrient management. In addition, rice varieties currently used for DSR are primarily selected and bred for puddled transplanted rice. Risks associated with a shift from puddled transplanting to DSR include (1) a shift toward hard-to-control weed flora, (2) development of herbicide resistance in weeds, (3) evolution of weedy rice, (4) increases in soil-borne pathogens such as nematodes, (5) higher emissions of nitrous oxide—a potent greenhouse gas , and (6) nutrient disorders, especially N and micronutrients. The objectives of this chapter are to review (1) drivers of the shift from puddled transplanting to DSR; (2) overall crop performance, including resource-use efficiencies of DSR; and (3) lessons from countries where DSR has already been widely adopted. Based on the existing evidence, we present an integrated package of technologies for Dry-DSR, including the identification of rice traits associated with the attainment of optimum grain yield with Dry-DSR.
The mechanization of rice production in China has been accompanied by a rapid reduction in agricultural labor forces and increase in machinery purchase subsidies; however, the comprehensive ...performance of several major mechanized production modes regarding output, environmental protection, and profit remains uncertain to the Chinese government and farmers alike. Here, a five-year (2015–2019) field experiment was conducted to analyze the performance of farmers' mechanized seedling transplanting (FMST), farmers' mechanized direct seeding (FMDS), and reduced-input direct seeding (RIDS) concerning grain yield, energy use, greenhouse gas emissions, and economic benefits. RIDS used an unmanned aerial vehicle for sowing, fertilizing, and spraying, while adopting no-tillage, bed-furrow irrigation technology. The quantity and stability of RIDS-produced grain were similar to those of FMST and higher than those of FMDS. Furthermore, RIDS yields required significantly less machinery, human labor, fuel, and water, with 34.72% and 24.03% decreases in total energy input compared to that for FMST and FMDS, corresponding to 1.45- and 1.34-fold increases in energy productivity, respectively. The resulting CO2-eq emissions from agricultural inputs for RIDS were 71.26% and 71.32% of those for FMST and FMDS, while CH4 emissions were 32.60% and 29.24% of those for FMST and FMDS, respectively. Despite the high N2O emissions and decomposing trend of soil organic carbon in RIDS, the net global warming potential still decreased by 48.84–58.36%, and the carbon sustainability index and carbon efficiency ratio increased by 87.67–142.14% and 105.32–188.22%, respectively, compared with those of FMST and FMDS. RIDS had the lowest cost, its net return was USD 298.81 ha−1 higher than that of FMDS (similar to FMST), and its benefit-cost ratio was 10–36.19% higher than that of FMST and FMDS. Generally, RIDS offered a higher-yielding, cleaner, more sustainable rice production technology for meeting the needs of the Chinese government and farmers.
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•The performance of several mechanized rice production modes in China is unknown.•A 5-year field experiment was conducted to assess the performance of three methods.•Yields, energy use, greenhouse gas emissions, and economic benefits were assessed.•Reduced-input direct seeding offered the most advantages in the assessed metrics.
To investigate the development direction of mechanized rice production in China, we compared the differences between two production modes, namely, unmanned aerial vehicle direct seeding (UDS) and ...integrated mechanical transplanting (IMT) in energy use efficiency (EUE) and economic benefits from 2017 to 2019. Fertilizer, fuel, and water account for the top three largest proportions of total energy input under both production modes. The energy inputs in fuel, irrigation water, and plastic film under UDS were 4611.34 MJ ha−1, 1355.21 MJ ha−1, and 3913.02 MJ∙ha−1 lower than those under IMT, respectively. The application of transplanting and fertilizer-pesticide spraying integration machine under IMT contributed to its energy-saving advantages in electricity, fertilizer and pesticide; however, the energy inputs in these three aspects were only reduced by 30.74 MJ ha−1, 355.98 MJ ha−1 and 69.34 MJ ha−1, respectively. The total energy input under IMT from 2017 to 2019 was 45.11%–45.69% higher than that under UDS. There was no significant difference in rice grain yield and straw yield. The EUE, energy productivity and energy profitability under UDS were 41.03%, 41.87%, and 46.69% higher than those under IMT, respectively. The cost under UDS was 13.8% lower than that under IMT. In addition, under UDS, the net return was 7.5% higher, and the benefit-to-cost ratio was 24.7% higher. Energy input and cost under UDS were reduced compared with those under IMT on the premise of stable yield. It can be concluded that IMT is a more promising mechanized rice production mode in China.
•Performances of IMT and UDS were analyzed in a three-year field experiment.•Grain yield and rice straw via UDS was similar to that in IMT.•Energy input under UDS was 31.19% (10061.38 MJ ha−1) lower than that under IMT.•UDS had significant lower cost with net return of US $2253.81 ha–1•UDS is a high-yield and high-profitability production mode.
•Rice yield was not affected by planting method (dry seeding or non-puddled transplanting).•Irrigation input was relatively higher in DSR than in NPTR in all the seasons.•Increase in irrigation water ...productivity and input water productivity with alternate wetting and drying.•High the potential of hybrids for non-puddled system.
Increasing farm labor scarcity and depletion of natural resources such as water are posing a major threat to the sustainability of traditional puddled transplanted rice (PTR) farming in Eastern India. Dry-seeded rice (DSR) or non-puddled transplanted rice (NPTR) could be used as an alternative to PTR. To understand the trade-off with different water management and rice genotypes under non-puddled conditions, a field experiment was conducted during 2014–2015 on a sandy clay loam soil of Bhubaneswar, Odisha. The treatments for water regimes were based on soil water tension (no stress, 10kPa, and 40kPa) at 15-cm soil depth and the cultivars used in the study were inbreds (Lalat and Sahbhagi Dhan) and hybrids (Arize® 6129, 6444, and US 323).
In both years, rice yields were higher in the dry season than in the wet season. However, both establishment methods performed similarly in all the seasons. With an increase in water stress, there was a significant decline in yield and yield attributes in the dry season. Irrigation input in the dry season was roughly more than double that in the wet season. Irrigation input was relatively higher in DSR than in NPTR in all the seasons, which might be because of an extra irrigation required for DSR crop establishment than for transplanting in non-puddled conditions where watering is done only for ease of transplanting. There was irrigation saving of 25% and 58% in 10kPa and 40kPa, respectively, compared to no stress in the dry season. A consistent trend of an increase in irrigation water productivity (WPI) and input water productivity (WPI+R) was observed with an increase in stress. Arize® 6444 produced the highest grain yield, irrigation and input water productivity, and its performance was also better in terms of tiller density, LAI, and biomass. Our findings highlight the potential of hybrids compared with inbreds and their performance under DSR was found to be superior. Even though the yield in no stress was slightly higher than in 10andkPa, the irrigation water savings in 10kPa were distinctly significant.
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