Rice yields decline with higher night temperature from global warming

The impact of projected global warming on crop yields has been evaluated by indirect methods using simulation models. Direct studies on the effects of observed climate change on crop growth and yield could provide more accurate information for assessing the impact of climate change on crop production. We analyzed weather data at the International Rice Research Institute Farm from 1979 to 2003 to examine temperature trends and the relationship between rice yield and temperature by using data from irrigated field experiments conducted at the International Rice Research Institute Farm from 1992 to 2003. Here we report that annual mean maximum and minimum temperatures have increased by 0.35°C and 1.13°C, respectively, for the period 1979–2003 and a close linkage between rice grain yield and mean minimum temperature during the dry cropping season (January to April). Grain yield declined by 10% for each 1°C increase in growing-season minimum temperature in the dry season, whereas the effect of maximum temperature on crop yield was insignificant. This report provides a direct evidence of decreased rice yields from increased nighttime temperature associated with global warming

Influence of the Cyclic Loading Path on Rock Deformation Memory Effect

Deformation rate analysis utilizes deformation memory effect (DME) that is one of the fundamental properties of rock, to estimate in situ stress underground. It could be influenced by the stress history which has been subjected to in the past. To understand the influence under the cyclic loading path, in the experimental study, different stress levels were applied on sandstone samples and two types of granite samples. In the theoretical investigation, the sliding friction model consisting of multiple microstructure surfaces is considered in this paper. Both experiments and the theoretical model show that when the number of cyclic loading times keeps increasing, (1) the stress read at the DRA inflection is getting closer to the previously cyclic stress; (2) the angle at the DRA inflection becomes sharper, which gives clearer inflection point; and (3) the strain differential amplitude in the DRA curve gradually decreases and then toward a stable value. An upper limit exists for influence, indicating that the best cyclic loading times occur when the pulse amplitude of the strain differential stops changing. It is confirmed that the multiple cyclic loading method provides a better outcome for experiment using artificial preload when DME is utilized for stress reconstruction. Without other factors disturbing, the memory information of the in situ stress would hardly lose under the history of cyclic loading

Responses of Soil Organic Carbon Sequestration Potential and Bacterial Community Structure in Moso Bamboo Plantations to Different Management Strategies in Subtropical China

Moso bamboo is one of the fastest-growing plants in the world. The objective of this study was to investigate the impact of converting secondary broadleaf evergreen forests (CK) to Moso bamboo plantations, and the impact of different management strategies, including no disturbance (M0), extensive management (M1), and intensive management (M2), on the soil organic carbon (SOC) sequestration potential, and relevant characteristics of the soil bacterial community. Our results showed that, in comparison with CK, M0 and M1 had significantly higher SOC and recalcitrant organic materials (aliphatic and aromatic compounds), and a lower C mineralization rate, whereas M2 had the opposite effects. The conversion from CK to Moso bamboo plantation significantly decreased the relative abundance of Acidobacteria in both the topsoil and subsoil soil layers. Compared with CK, M0 led to the enrichment of bacteria such as Alphaproteobacteria, Chloroflexi, and Bacteroidetes, which are involved in the decomposition of organic matter and the formation of humus and are, therefore, potentially beneficial for increasing the SOC. Furthermore, the ratio of the microbial biomass C (MBC) to total organic C (TOC), C mineralization rate, and bacterial diversity increased from M0 to M2, i.e., with an increase in the disturbance intensity. These findings indicate that the conversion of secondary broadleaf forest to bamboo forest alter the soil bacterial community structure. Reducing disturbance in bamboo forest management strategies should be actively taken up to improve the SOC, and maintain sustainable development in the forest industry

Grain Yield and Nitrogen Use Efficiency of Late-cropping Rice in Response to Delayed Application of Nitrogen and Altered Plant Spacing in South China

【Objective】In order to further enhance grain yield of rice and nitrogen (N) use efficiency (NUE), N fertilizer was reduced and topdressing was delayed, together with alteration in row and plant spacing and planting density.【Method】In two late seasons, comparison trials were conducted with 8 treatments, including zero applied N (T1), farmers' practice (T2, control), 3 moderately-delayed N topdressing (T3-T5) and 3 highly-delayed N topdressing (T5-T8). T3-T8 also had alteration in N application rate, planting density and row and plant spacing.【Result】In comparison to T2, the average grain yields under T3-T5 were increased by 29.7% and 15.9%, and those of T6-T8 were increased by 26.4% and 18.6% in two late seasons, respectively. In both late seasons, nitrogen uptake and plant growth under T3-T5 and T6-T8 were slower before panicle initiation and they were both increased or accelerated thereafter. Based on average results in two late seasons, leaf area indexes at heading stage were enhanced by 8.5% and 11.8% respectively under T3-T5 and T6-T8 compared with that under T2. Leaf nitrogen contents at heading stage were enhanced by 16.8% and 23.5%, respectively. The numbers of panicles per hectare were increased by 14.5% and 15.2%, panicle size remained unchanged or was increased by 12.5%, sink sizes were increased by 13.6% and 29.3%, seed setting rate was enhanced by 9.0% or remained the same, 1000-grain weight remained identical or was decreased by 9.0%, biomasses were increased by 14.8% and 15.5%, and harvest indexes were increased by 7.2% and 6.4%, respectively. The total amounts of N uptake were increased by 27.6% and 40.7%, N uptake efficiencies were increased by 85.9% and 124.2%, agronomical efficiencies were increased by 99.1% and 102.5%, and partial factor productivity was increased by 32.1% and 36.2%, respectively. Additional N input, dense planting and alteration in row and plant spacing had little effect on yield and NUE. Highly-delayed N topdressing could further expand sink size and improve NUE, but could not enhance grain yield anymore.【Conclusion】With reduced N input, both source and sink of rice were substantially enlarged, and the yield and NUE were dramatically increased under moderately-delayed and highly-delayed N topdressing

Effect of different inter-satellite range on measurement precision of Earth’s gravitational field from GRACE

The precision of Earth’s gravitational field from GRACE up to degree and order 120 was studied for different inter-satellite ranges using the improved energy conservation principle. Our simulated result shows that; For long wavelength (L ⩽ 20) at degree 20, the cumulative geoid-height error gradually decreased with increasing range, from 0. 052 cm for 110 km to 1. 156 times and 1. 209 times as large for 220 km and 330 km, respectively. For medium-wavelength (100 ⩽ L ⩽ 120) at degree 120, the cumulative geoid-height error decreased from 13. 052 cm for 110 km, to 1. 327 times and 1. 970 times as large for the ranges of 220 km and 330 km, respectively; By adopting an optimal range of 220±50 km, we can suppress considerably the loos of precision in the measurement of the Earth’s long-wavelength and medium-wavelength gravitational field

Parameterization, Validation and Comparison of Three Tillering Models for Irrigated Rice in the Tropics

Tillering plays an important role in determining rice grain yield. Several models have been developed to predict tiller production in irrigated rice. In this paper we tested three models using data drawn from a wide range of plant densities and N inputs in two field experiments conducted at the International Rice Research Institute, Philippines during the 1997 and 1998 dry seasons. Two rice cultivars (IR64 and IR72) were used in the experiments. Plant samples were taken at intervals to determine number of tillers, leaf area index (LAI), biomass, relative growth rate (RGR) and leaf N concentration. The models were parameterized using an iteration procedure of the simplex method. Previous models (TIL and SINK) using the original values of parameters for IR64 failed to predict the number of tillers of IR64 in 1997. However, when re-parameterized, both models described the 1997 data well for both cultivars. The two models also predicted fairly well the number of tillers of different transplanting spacing and N input treatments of IR72 in 1998 using IR72 parameters derived from the 1997 experiment. A simple RGR model was comparable with the TIL and SINK models in descriptive and predictive ability. It appears that all three models could be used for predicting tiller production of irrigated rice

Analysis on Screening of Suitable Varieties for Rice Ratooning and Yield Components under Different Cutting Heights in North Guangdong

【Objective】Based on the evaluation of growth period and grain yield performance of ratooning rice under different cutting heights, suitable varieties were selected for ratooning rice production in North Guangdong.【Method】Thirty-four rice varieties (bred or approved in Guangdong Province) were selected for tests under mid- or low-stubble cutting heights. The growth period, grain yield and yield components under different cutting heights among the tested varieties were investigated.【Result】The main crop yield was 5 210.9-8 566.8 kg/hm2, and grain yield of Huangguanghuazhan 1 was the highest. The ratoon crop yield of low-stubble ratooning rice was 3 335.0-6 357.3 kg/hm2, 16.1% higher than that of mid-stubble ratooning rice (2 084.4-5 940.5 kg/hm2). Qingxiangyou 19 Xiang was the highest in ratoon crop yield under both cutting heights. According to cluster analysis, the ratoon crop yield and total annual grain yield under mid-stubble ratooning rice mode could be categorized to four major groups, namely, high-yield, mid-high-yield, medium-yield, and low-yield levels. Each group contained 4, 7, 18, and 5 varieties for ratoon crop yield and contained 1, 14, 14, and 5 varieties for total annual grain yield under mid-stubble ratooning rice mode. Under low-stubble cutting height, the ratoon crop yield was also categorized to four major groups with 2, 17, 14 and 5 varieties, while the total annual grain yield was divided into three major groups, containing 10, 21, and 3 varieties, respectively. In ratoon season of low-stubble ratooning rice, the growth period was prolonged by an average of 9.1 days, the number of spikelets per panicle was increased, and the effective panicles and seed setting rate were reduced compared with those in ratoon season of mid-stubble ratooning rice. Under mid-stubble cutting height, the ratooning rice regenerated from the 3rd, 4th, and 5th nodes from the top (D3, D4 and D5) contributed 4.7%, 33.3%, and 62.0% of the total grain yield per plant, respectively. Under low-stubble cutting height, the ratooning rice regenerated from D3, D4, and D5 contributed 0%, 11.9%, and 88.1% of the total yield per plant.【Conclusion】If assessed with the criteria of high- or mid-high-level ratoon crop yield and high-level total annual grain yield, 9 rice varieties, including Huangguangyouzhan, Huangguanghuazhan 1, Huangguangtaizhan, Wuyouyuehesimiao, Guang 8 Youjinzhan, Hengfengyou 387, Qingxiangyou 003, Qingxiangyou 132, and Qingxiangyou 19 Xiang are recommended for production of mid-stubble ratooning rice. Ten rice varieties, including Erguangyouzhan 3, Huangguangyouzhan, Huangguanghuazhan 1, Huangguangtaizhan, Yuehesimiao, Nanjingzhan, Yuetaiyouzhan, Wuyouyuehesimiao and Guang8youjinzhan are suitable for production of low-stubble ratooning rice. For mid-stubble ratooning rice, new tillers mainly regenerate from the 4th nodes from the top and other lower nodes below. For low-stubble ratooning rice, new tillers mainly regenerate from the 5th nodes and other lower nodes below

Leaf-Associated Shifts in Bacterial and Fungal Communities in Response to Chicken Rearing Under Moso Bamboo Forests in Subtropical China

Integrated bamboo-chicken farming (BCF) systems are a traditional agroforestry pattern with large economic benefits in subtropical China. However, little is known regarding the effect of this integration on the bamboo leaf-associated microbiome, which can be very important for disease control and nutrient turnover. In the present study, we compared the leaf-associated bacterial and fungal communities of moso bamboo (Phyllostachys edulis) in a BCF system and an adjacent moso bamboo forest (MBF). The results showed that Cyanobacteria and Ascomycota were the predominant microbial phyla associated with bamboo leaves. Chicken farming under the bamboo forest significantly increased the bacterial and fungal alpha diversity (observed operational taxonomic units (OTUs) and Simpson’s index) associated with bamboo leaves. Principal components analysis (PCoA) further confirmed the shifts in the bacterial and fungal communities caused by chicken farming. Based on the observed relative abundances, the phyla Bacteroidetes, Actinobacteria, TM7, and Basidiomycota were significantly increased on BCF-associated leaves compared with MBF leaves, while Acidobacteria and Ascomycota were significantly decreased. An ecological function prediction analysis based on metabolic processes indicated that BCF could accelerate nutrient (C, N, and S) cycling but may increase the risk of fungal-associated diseases. Our findings suggest that shifts in leaf-associated bacterial and fungal communities can be important indicators for the scientific management of BCF systems

Changes of Root Endophytic Bacterial Community Along a Chronosequence of Intensively Managed Lei Bamboo (Phyllostachys praecox) Forests in Subtropical China

Endophytic bacteria widely exist inside plant tissues and have an important role in plant growth and development and the alleviation of environmental stress. However, little is known about the response of root-associated bacterial endophytes of Lei bamboo (Phyllostachys praecox) to intensive management, which is a common management practice for high bamboo shoot production in subtropical China. In this study, we comparatively investigated the root endophytic bacterial community structures in a chronosequence of intensively managed (5a, 10a, 15a, and 20a) and extensively managed plantations (as control, Con). The results showed that endophytic Proteobacteria was the dominant bacterial phylum in the bamboo roots. Intensive management significantly increased (p < 0.05) the bacterial observed species and Chao1 (except 5a) indices associated with bamboo roots. The relative abundances of Firmicutes, Bacteroidetes, and Actinobacteria (except 15a) in the intensively managed bamboo roots significantly increased (p < 0.05) compared with those in Con, while the relative abundance of Proteobacteria significantly decreased in intensively managed bamboo roots (p < 0.05). The phyla Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes were the biomarkers in Con, 5a, 15a, and 20a, respectively. Redundancy analysis (RDA) showed that soil alkali-hydrolysable N (AN), available phosphorus (AP), available K (AK), and total organic carbon (TOC) were significantly correlated (p < 0.05) with the bacterial community compositions. Our results suggest that the root endophytic microbiome of Lei bamboo was markedly influenced by intensive management practices, and the available nutrient status could be the main driving factor for such shifts. Although heavy fertilization in the intensive management system increased the diversity indices, the rapid changes in root endophyte communities and their relevant functions might indicate a high risk for sustainable management