Effects Of Long Term Crop Cultivation Techniques On Sustainable Production Of Super Rice Under Rice-Rape Cropping System

1. Tillering Characters and Grain Yield of Super Hybrid Rice LiangyoupeijiuAt maximum tillering (Max.) and at maturity (MA) stage, direct seeding (DS) resulted in22%more tillers than transplanting (TP) irrespective of tillage system. Tiller mortality reached at peak between panicle initiation (PI)-booting (BT) stages, and was16%higher under conventional tillage (CT) than under no-tillage (NT). Transplanting required29%more time for the completion of tillering and less for DS. Tillering rate was43%higher in DS than TP under either CT or NT. There was a positive correlation between panicle number per m2and maximum tiller number per m2, but not to panicle-bearing tiller rate. The panicle bearing tiller rate was higher under DS than TP and higher under NT than CT. Tiller dry weight gradually increased up to heading (HD) stage, and was14%higher under TP than DS. Grain yield was higher under CTTP owing to the larger sink size (heavier panicle, more spikelets in per cm length of panicle) than under2. Functional Leaf Characters and Leaf Photosynthetic Response of Super Hybrid Rice LiangyoupeijiuTP had positive influence on length and width of functional leaf. Taller and wider functional leaf was found in CTTP followed by NTTP. Leaf area of third leaf was higher than second and flag leaf. N concentration was higher in flag leaf than second and third leaf as well as CTTP than other cultivation techniques. There were two peaks in leaf photosynthesis, the first peak was found at Max. and another was at HD stage except NTTP. Source capacity (functional leaf area per spikelet and aboveground biomass per spikelet) were33%and17%higher in DS than TP.3. Growth and Physiological Responses of Super Hybrid Rice LiangyoupeijiuLAI (leaf area index) was higher at BT (booting) in TP and at HD (heading stage) in DS method both in CT and NT system. LAD (leaf area duration) was higher in DS both in CT and NT system. DS produced more above ground biomass than TP but at MA (maturity stage), both CTTP and NTDS had higher above ground biomass. CGR (crop growth rate) was higher at PI (panicle initiation stage)-BT stage in TP either in CT or NT but was higher at PI-HD in DS. NAR (net assimilation rate) was15%and24%higher in NTTP than CTTP at PI-BT stage and BT-HD respectively but CTTP had15%higher NAR than NTTP at HD-12DAH. In CTTP, higher leaf N concentration (2.04%) and uptake (5.9g m-2) were observed at BT stage. In DS, N concentration and uptake was always higher in NT at all growth stages. 4. Grain Filling Pattern of Super Hybrid Rice LiangyoupeijiuSuperior grain weight of TP either in CT or in NT gradually increased up to30days after heading (DAH) and then sharply increased at30-36DAH but in DS, it increased gradually up to24DAH and sharply increased at24-30DAH. Grain weight both superior and middle grain was higher in TP either in CT or in NT than DS up to12DAH but was higher in DS than TP at30DAH. At36DAH, superior grain weight of NT system either in TP or in DS was slightly heavier than CT. Inferior grain weight increased slowly at early grain filling stage but grain filling increased sharply at later grain filling period and was closed to superior grain in DS either in CT or in NT. Grain filling rate of superior and middle grain was higher in TP either in CT or NT at18DAH and NTDS had slightly higher than CTDS but they were statistically identical. Grain filling rate of inferior grain in TP was higher at36DAH but was higher at30DAH in DS. Grain filling rate was higher in superior grain both in TP (1.03mg grain-1day-1) and DS (0.96mg grain-1day-1). In middle grain, it was0.68mg grain-1day-1in TP and0.70mg grain-1day-1in DS. But in inferior grain, it was0.68mg grain-1day-1in TP and0.90mg grain-1day-1in DS.5. Changes of Soil Properties and Root ActivityBulk density (BD) decreased from2004-2012by31.2%in NT and8.1%in CT system but17.8%in TP and22%in DS respectively at0-5cm soil depth. But it was increased from2004-2012by6.3%in NT and2.7%in CT system at5-10cm soil depth. Similarly, BD increased by10.9%in NT and7.8%in CT system but8.3%in TP and10.3%in DS respectively at10-20cm soil depth. NT caused root accumulation in the surface soil layer (0-5cm) under both in TP and DS owing to compaction of soil at the lower horizon and could lead to an accelerated soil acidification compared to CT, especially at the0-5cm soil depth. NT had about10%more OM (organic matter content) than CT at0-5cm soil depth but it was about22%and7%higher in CT than NT at5-10cm and10-20cm soil depth. At the top layer (0-5cm) of soil, NT had higher active organic carbon (AOC) than CT both in TP and in DS owing to content of more OM. Towards deeper soil depth, AOC increased by about23%and14%in CT at5-10cm and10-20cm soil depth respectively owing to content of higher OM. Total N had about16%and14%higher in NT than CT at0-5and10-20cm soil depth and available N had about10%higher in NT than CT at0-5cm soil depth but it was about20%higher in CT than NT at5-10cm soil depth. Available P content was higher in CT than NT at5-10cm and10-20cm soil depth but there was no consistent difference in available P at0-5cm soil depth. Available soil K decreased from surface to lower layer of soil. At all soil depth, CTTP, NTTP and NTDS were statistically similar and CTDS was lower but CTTP had higher amount of available K. CTTP had highest root oxidation activity in all growth stages except PI stage.6. Weed Seed Bank size and composition under Long Term Rice-Rape Cropping SystemThe weed seed accumulation of most species was highest in the0-5cm soil depth. More than60%(%to total) weed seeds were germinated at20days after placement of Tray (DAP). The seed bank size of Echinochloa crus-galli (L) Beauv under DS was53%higher than TP in both years. It decreased67%under CT and87%under NT from0-5to5-10cm soil depth during2011. The ranked of weed species were grass> broad leaf> sedge based on their number per unit area in both years. The rank of Echinochloa crus-galli (L) Beauv (barnyardgrass) was CTDS> NTTDS> NTTP> CTTP among the treatments at0-5cm soil depth in both years. Monochoria vaginalis (Burm.f) Kunth, Fimbristylis miliacea (L) Vahl and C. iria L were fewer in number. The pressure of germination of weed seeds was more at20DAP at0-5cm soil depth. Total number (up to60DAP) of Echinochloa crus-galli (L) Beauv was higher in CTDS at0-5cm soil depth in both years and drastically reduced under NT than under CT towards deeper horizon of soil.7. Impact of Long Term Cultivation Techniques on Sustainable Production of Super Rice under Rice-Rape Cropping SystemMaximum tiller number per m2was about33%higher in DS than TP. CTTP had about12%more tillers than NTTP at Max. stage. TP had15%higher Panicle-bearing tiller than DS. The more panicle number per m2of DS was attributed by higher number of maximum tiller per m2but not by higher panicle-bearing tiller rate. Spikelet production efficiency was about24%higher in TP over DS irrespective of tillage system. At HD, dry matter was8%higher in CTTP than NTTP as well as CTDS than NTDS. At MA, it was5%higher in CTTP than NTTP. Mean panicle number per m2in CTTP was less than CTDS by21%and NTTP was less than NTDS by28%. CTTP had about7.5%more panicles than NTTP. Mean spikelet number per panicle under CTTP was24%higher than CTDS and23%higher in NTTP than NTDS. Finally, long term tillage and crop establishment methods had no significant influence on mean grain yield variation across the years.