Effects Of Integrated Crop Management,Climatic Conditions,and Soil Fertility On Dry Matter Production And Yield Formation Of Double-Season Rice And The Related Mechanism

Rice is the staple food for more than half of the world’s population,making a significant contribution to global food security.Rice production is facing great challenges due to the growing population and the threat of climate change.China has huge rice planting areas with significant differences in soil fertility,which results in great effects on the rice grain yield.Super-high yielding practice has been intensively studied for single-season rice cropping system,and has brought about large increase in rice yield.However,little is known about yield performance and resource use efficiency of double-season rice under super-high yielding practice.In order to determine the effects of crop management practices and soil fertility on the grain yield,biomass production,radiation use efficiency,and nitrogen use efficiency(NUE)of double-season rice,field experiments were conducted in the early and late seasons of 2012-2014 at Wuxue County(Hubei Province,China).In the field experiments at Wuxue,Liangyou287 was used in the early season and Tianyouhuazhan in the late season.Field experiments were conducted in one field with high soil fertility in 2012-2014,and in additional two fields with medium and low soil fertility in 2014.There were three crop management practices(NO,FP,and SH)in the experiment.NO,FP,and SH represent zero-N,farmer’s practice,and super-high yielding practice,respectively.Crop management treatments were arranged in a complete randomized block design with four replicates.Moreover,the effects of temperature and radiation on dry matter production and yield formation of double-season rice were examined,through the comparison of double-season rice crops under SH in Wuxue and IRRI(International Rice Research Institute,Los Ba?os,Philippines).The data of IRRI was from the field experiments in the dry and wet seasons of 2008-2010.The results of this research are as follows: 1)Effects of crop management practices on yield formation of double-season riceThe annual grain yield of double-season rice crop under SH reached 18.85-20.19 t ha-1,close to the yield potential of double-season rice.The average rice yield under SH in single season was 9.8-16.0% higher than that under FP.The yield advantage of SH resulted from a combination of increases in sink size due to more panicles per unit area and biomass production due to higher crop growth rate,while it was not related to growth duration,harvest index,and other yield components.The improvements in sink size and biomass production under SH were supported by the increased tillering rate and tiller number during the early growth period,and the increased leaf area index,crop growth rate,and radiation use efficiency(the ratio of dry matter accumulation and total intercepted radiation)during pre-and post-flowering periods compared with FP.Compared with that under FP,dry matter accumulation of rice during pre-and postflowering periods under SH were increased by 15.2-30.6% and 12.1-48.8% in early season,and 30.5-41.7% and 5.6-17.5% in late season,respectively.High radiation utilization efficiency and biomass production of the double-season rice under SH were mainly attributed to the optimal leaf area index,low canopy extinction coefficient,and slow attenuation of leaf SPAD value and leaf area index during post-flowering period.Double-season rice under SH showed great N accumulation and translocation due to large pre-flowering N accumulation and translocation,instead of high post-flowering N accumulation,pre-flowering N translocation efficiency,contribution of pre-flowering N translocation to grain N.In high N input and planting density conditions,double-season rice under SH had higher agronomic N use efficiency,and similar N recovery efficiency,physiological N use efficiency,and NUE for biomass production compared with FP.The results indicated that SH had greater yield increase due to its higher nitrogen accumulation and utilization ability compared with FP.2)Effects of temperature and radiation on grain yield of double season rice in subtropical and tropical environmentsIn current study,grain yields of double-season rice in the tropical and subtropical environments were close to the climatic yield potential in a given season.Grain yield was 9-66% higher in the subtropics than in the tropics.Both of sink size and biomass production were responsible for the yield difference between the tropical and subtropical environments.Crop growth duration and harvest index did not explain the high grain yield of double-season rice under subtropical conditions.The improved sink size and biomass production in the subtropics were due to that panicles per m2 and solar radiation use efficiency(the ratio of dry matter accumulation and total incident solar radiation)were 13% and 48% higher than that in tropics,respectively.The average daily minimum and maximum temperatures from transplanting to maturity at IRRI were 3.4 and 1.9 oC higher than that at Wuxue,respectively.Overall,average daily solar radiation and seasonal solar radiation from transplanting to maturity at Wuxue was lower or similar to that at IRRI.Across sites,seasons,and years,both grain yield and solar radiation use efficiency were significantly correlated with average daily minimum and maximum temperatures,but were not correlated with average daily solar radiation from transplanting to maturity.Grain yield declined significantly when average daily minimum and maximum temperatures were greater than 22.0 and 29.5 oC,respectively.Among the climatic parameters,temperature rather than solar radiation was responsible for the differences in grain yield and radiation utilization between the two environments.Higher temperature in the tropics reduced solar radiation use efficiency significantly,which led to the lower biomass production and grain yield in the tropical environment.3)Effects of soil fertility on yield formation of double-season riceRice yield significantly decreased with the decrease of soil fertility.Grain yield of double-season rice under SH was affected by soil fertility.High soil fertility was an important factor for achieving the yield potential of the double season rice.The rice yield under SH was consistently higher than that under FP in high,medium,and low soil fertility conditions.However,the yield differences between SH and FP showed inconsistent trend among the soil fertility conditions.Soil fertility mainly affected biomass production and sink size instead of harvest index,spikelets per panicle,grain filling rate,and grain weight.The differences between SH and FP in tiller number per unit area,leaf area index,radiation use efficiency,dry matter accumulation were consistently increased with the increase of soil fertility.Double-season rice under different soil fertility conditions showed great differences in N accumulation,but not in N translocation and utilization.The differences in N translocation and utilization between SH and FP showed inconsistent responses to soil fertility conditions.High soil fertility together with optimized crop management practice were the essential factors for the super high yielding rice production.4)ConclusionCrop management practices,climatic conditions,and soil fertility have significant effects on double-season rice yield by affecting source and sink production.Solar radiation utilization efficiency and panicles per unit area are the main factors resulting in the difference insource and sink production between SH and FP,respectively.High temperature significantly reduces solar radiation use efficiency and biomass production capacity.High soil fertility significantly improves biomass production capacity.Therefore,optimized crop management practice,cool temperature,and high soil fertility are indispensable factors to super high yielding rice production.The future studies should pay more attentions on the optimization of crop management,physiological mechanisms of the effects of temperature elevation on grain yield of double season rice,and the interaction between crop management practices and soil fertility on grain yield of double season rice.