Tian Yc

Climatic warming increases winter wheat yield but reduces grain nitrogen concentration in east China.

Climatic warming is often predicted to reduce wheat yield and grain quality in China. However, direct evidence is still lacking. We conducted a three-year experiment with a Free Air Temperature Increase (FATI) facility to examine the responses of winter wheat growth and plant N accumulation to a moderate temperature increase of 1.5°C predicted to prevail by 2050 in East China. Three warming treatments (AW: all-day warming; DW: daytime warming; NW: nighttime warming) were applied for an entire growth period. Consistent warming effects on wheat plant were recorded across the experimental years. An increase of ca. 1.5°C in daily, daytime and nighttime mean temperatures shortened the length of pre-anthesis period averagely by 12.7, 8.3 and 10.7 d (P<0.05), respectively, but had no significant impact on the length of the post-anthesis period. Warming did not significantly alter the aboveground biomass production, but the grain yield was 16.3, 18.1 and 19.6% (P<0.05) higher in the AW, DW and NW plots than the non-warmed plot, respectively. Warming also significantly increased plant N uptake and total biomass N accumulation. However, warming significantly reduced grain N concentrations while increased N concentrations in the leaves and stems. Together, our results demonstrate differential impacts of warming on the depositions of grain starch and protein, highlighting the needs to further understand the mechanisms that underlie warming impacts on plant C and N metabolism in wheat.

Super Rice Cropping Will Enhance Rice Yield and Reduce CH4 Emission: A Case Study in Nanjing, China

A pot experiment was performed to learn the differences in plant productivity and CH4 emission between two rice cultivars, super rice variety Ningjing 1 and traditional variety Zhendao 11, which were currently commercially applied in Nanjing, China. Similar seasonal changes of CH4 emission fluxes and soil solution CH4 contents were found between the tested cultivars. Although there was no significant difference in plant biomass production between the cultivars, the grain yield of Ningjing 1 was significantly higher by 35.0% (P < 0.05) than that of Zhendao 11, whereas the total CH4 emission from Ningjing 1 was 35.2% lower (P < 0.05). The main difference in the amounts of CH4 emission between the cultivars occurred in the period from the tillering stage to the heading stage. The biomass-scaled and yield-scaled CH4 emissions were respectively 3.8 and 5.2 mg/g for Ningjing 1, significantly lower than those for Zhendao 11 (7.4 and 12.8 mg/g, respectively). According to the relationships between the plant growth characteristics and the CH4 emission, a stronger root system contributed mainly to the lower CH4 emission of Ningjing 1, as compared with Zhendao 11. Our results demonstrated that super rice has advantages not only in grain productivity but also in CH4 emission mitigation. Further expansion of super rice cropping will enhance rice yield and reduce greenhouse gas emission in China.

Effect of rice panicle size on paddy field CH4 emissions

Developing large rice (Oryza sativa L.) panicles has been widely regarded as an effective approach to increasing rice yield. However, it is unclear whether panicle size affects CH4 emissions from rice fields, especially during the reproductive stage. Here, we conducted two experiments (rice variety and mutant) to examine the effects of rice panicle size on CH4 emissions. The variety experiment under field conditions at two sites showed that rice yield was significantly and positively correlated with the spikelet number. Mean CH4 emissions during the reproductive stage were significantly and negatively correlated with spikelet number. The rice mutant experiment under pot and field conditions using a wild-type rice variety (WT) and its mutant (Mutant) demonstrated that CH4 emissions were significantly lower in the former with large panicles than in the later with small panicles, during the reproductive and grain filling stages (P < 0.01), whereas the rice yields showed an opposite. Root exudates and soil dissolved organic C concentration were significantly lower under the WT than under the Mutant. Soil CH4 production potential and mcrA gene copy number of the soil under Mutant were significantly higher than those of the soil under WT. There was no significant difference in soil CH4 oxidation potential and pmoA gene copy number between soils of these two rice varieties. Our results suggest that developing large panicles would benefit rice production for high yield with low CH4 emission.

Impacts of Nighttime Warming on the Soil Nematode Community in a Winter Wheat Field of Yangtze Delta Plain, China

Abstract Changes in the soil nematode community induced by global warming may have a considerable influence on agro-ecosystem functioning. However, the impacts of predicted warming on nematode community in farmland (e.g., winter wheat field) have not been well documented. Therefore, a field experiment with free air temperature increase (FATI) was conducted to investigate the responses of the soil nematode community to nighttime warming in a winter wheat field of Yangtze Delta Plain, China, during 2007 to 2009. Nighttime warming (NW) by 1.8°C at 5-cm soil depth had no significant impact on the total nematode abundance compared to un-warmed control (CK). However, NW significantly affected the nematode community structure. Warming favored the bacterivores and fungivores, such as Acrobeles, Monhystera, Rhabditis, and Rhabdontolaimus in bacterivores, and Filenchus in fungivores, while the plant-parasites were hindered, such as Helicotylenchus and Psilenchus. Interestingly, the carnivores/omnivores remained almost unchanged. Hence, the abundances of bacterivores and fungivores were significantly higher under NW than those under CK. Similarly, the abundances of plant-parasites were significantly lower under NW than under CK. Furthermore, Wasilewska index of the nematode community was significantly higher under NW than those under CK, indicating beneficial effect to the plant in the soil. Our results suggest that nighttime warming may improve soil fertility and decrease soil-borne diseases in winter wheat field through affecting the soil nematode community. It is also indicated that nighttime warming may promote the sustainability of the nematode community by altering genera-specific habitat suitability for soil biota.