Water And Nitrogen Utilization Characteristics In Dryland Rice

Field experiment and exact water-controlled pot experiment were conducted to learn about the characteristics water of and nitrogen utilization in dry-land rice. The field experiment was a split design with three replications. The main treatments included: traditional flooding cultivation (TF), non-flooded plastic film mulching cultivation (PM) and non-flooded and non-mulching cultivation (NM). The split plots was nitrogen rate: 0 kg N·hm^-2 (N1), 124kgN·hn^-2 (N2) and 150 kgN·hm^-2(N3). With TF and NM as control, PM were carried out to learn about its biological traits, N nutritional physiology, N, P and K use characteristics , some rice grain quality traits, under almost no irrigation condition during growth stage;The pot experiment was a randomized block design with five replications. The treatments included: traditional flooding (TF), plastic film mulching and flooding (MF), plastic film mulching and saturated water content (MS), plastic film mulching and 100% field water capacity (FWC) (M100), plastic film mulching and 90% FWC (M90), plastic film mulching and 80% FWC (M80), plastic film mulching and 70% FWC (M70). With TF as control, some studies were done about rice biological and yield traits, water utilization, anti-stress physiology, N, P, K utilization in rice, and soil fertility traits. The results showed as follows.Compared to NM, initiatory tillering was happened earlier and high-speed under PM, and the tillers, fertile ears, biomass and yield were significantly increased. Compared to TF, tillers and fertile ears under PM were almost no changed, and rice plant height and biomass decreased to some degree, available tiller rate and yield declined markedly. More N fertilizer, the biology and yield traits were improved, but the effect was less than cultivations, especially the water management.During growth stage, amino acid-N (AA-N) and nitrate-N(NO₃^--N) contents, nitrate reductase (NR), glutamine synthetase (GS), glutamic oxalacetic transferase (GOT), glutamic pyruvic transferase (GPT) activities in rice leaves of all treatments showed high at earlier stage. PM could increase the AA-N and NO₃^--N contents and the four enzymes activities over NM. As compared with TF, PM promoted the two forms N contents, NR and GS activities during earlier stage, and almost no change during later growth stage. During whole growth stage, GOT and GPT under PM had a declining and elevatory trend over TF respectively. With more N utilization, the two form N contents and four N- metabolizing enzymes were lightly higher.At mature stage, N concentrations and uptakes in rice grain and top three leaves blade (TTLB) were higher than other organs. P concentrations in leaves sheath on lower position (LSLP) under TF and in rice grain under dryland treatments (PM and NM) were highest of the rice organs, and P uptakes in grain under all treatments was higher than other organs. K concentration and uptakes in rice stem was highest, and that in grain was least of the rice organs. Compared with TF, total N, P and K uptakes of rice under PM significantly decreased by 19.5%, 30.4% and 20.8%, which was mainly due to the different biomass. Moreover, relative more N, P and K were stored in root and leaves on lower position (LLP). N, P concentration and uptakes in stem and top three leaves (TTL) were less for the more was transported to grain, so that of grain was increased relatively than TF. In that case, PM could promote N and P absorbed and transported to grain to some degree. However, K concentration and uptake, the percentage of K. uptake in grain were declined compared to TF. PM increased N, P and K uptakes markedly by 77.8%, 69.7% and 72.7% over NM, but the more was stored in root and source organs, the less was transported to grain, so Kconcentration and ratio were decreased slightly. In addition, fertilizer-N-recovery efficiency (REN), agronomic-N- use efficiency (AEN), physiological-N-use efficiency (PEN) and partial factor productivity of applied N (PFPN) under PM were slightly, significantly, significantly increased and markedly decreased compared to TF respectively. In comparison with NM, PM clearly increased REN, AEN and PFPN, but decreased PEN clearly.Gelatinization temperature (GT) and gelatinization enthalpy (GE) were no changed between different treatments. Cultivation and N level had large effect on rapid viscosity analyzer (RVA) profile of rice grain. Peak viscosity (PV), hot viscosity (HV), final viscosity (FV), breakdown (BV) and consistency (CV) of rice grain under NM increased over PM and TF. Compared to TF, PM significantly decreased the PV, markedly increased SV. Low and high N rate (N2 and N3") promoted HV in RVA profile of rice grain than zero N rate (Nl). Nl, N2 significantly increased and decreased BV and SV compared to N3 respectively. Generally, texture of dyland rice grain seemed to become hard and eating and flavor quality to inferior, and so did N fertilizer. In all, N rates have more effect on eating and flavor quality of rice than cultivation. Protein content of rice under PM clearly increased over NM, which significantly higher than TF. N rates had a positive effect on protein content of rice grain across all treatments.In pot experiment, MF could promote the tillers and rice plant height. With soil water content (SWC) declining, they were decreased, flag leaf chlorophyll and area were increased and decreased respectively. Proper SWC was helpful to increase available tillers. Biomass and yield in MF were significantly higher than other treatments, and biomass and yield decreased as FWC declined. Compared to MS, Ml00 and M90, the traits in TF almost no changed, but markedly increased over M70 and M80. As the FWC decreased, biomass of organs was declined too, and grain had most nearly correlation to flag leaf. Harvest index had little shift across the different FWC treatments, and film mulching treatments increased it over TF to different degree.Film mulching could promote soil temperature in pot (ST), which differed with weather and FWC. ST raised as FWC declined. Evaporation and transpiration (ET) of rice was least before middle tillering stage (MTS), much more from booting stage (BS) to flowering stage (FS), most during middle filling stage (MFS), and declined during two weeks to mature than MFS. ET of rice was decreased as FWC declined, and ET in MF slightly increased over TF. hi addition, ET had marked plus correlation with yield and biomass. Water use efficiency (WUE) for grain and biomass in M90 was higher than other treatments, significantly higher than TF and M70.Besides, SOD activity of leaf increased at filling stage (FS) than at BS, but POD and CAT activities decreased. As FWC declined, SOD activity increased at begain, then decreased from MS and M100 at BS and FS respectively. At BS, POD activity had higher sensitivity than at FS. It increased alone with FWC at BS, at FS it was contrary. POD activity under MF was markedly increased at BS and no change at FS compared to TF. At BS and FS, CAT activity was declined in company with FWC. Moreover, together with FWC, MDA, Pro and soluble protein contents of rice leaves were improved, but SS no regular dynamics.N concentration and uptake, P uptake in grain were clearly higher than other organs across all pot treatments. P concentration in root under flooded treatments (TF and MF) and in grain under the other treatments was highest. K concentration and uptake in stem was the highest of the organs among the treatments. N concentrations in all rice organs under M70 were significantly higher than other treatments. In company with FWC declining, N concentration of rice grain was increased, and that under TF was apt to least. Proper SWC promoted P concentrations in all rice organs. And P concentration in grain under MS was highest. K concentration in grain declined with FWC falling, and stem etc was in the contrary. As FWC dropping, N uptakes of rice plant decreased and then increased, P and K decreased, respectively. N, P and K uptakes of plant under MF were most, and N, P uptakes under Ml00 but K uptakes under M70 was least. N, P and Kuptakes in grain under MF and MS were more than other treatments. N uptake of grain under Ml00 was least, and so did P, K uptakes in grain under M70. Alone with FWC declining, the percentages of N, P uptakes in grain improved, and percentage K uptake in grain decreased. The PFP of applied N, P and K under MF treatments were highest than the other.At mature stage, different pot FWC had little effect on soil nutrient traits;Compared to transplanting stage, available K, P and N had some decline to a degree, and pH significantly increased at harvest stage. Film mulching treatments markedly increased the urease and alkaline phosphatase activities of soil, and those under M80 and M90 was highest across all treatments, respectively. Film mulching and flooded treatment increased catalse avtivity of soil, but other non-flooded treatments have little effect on it. At harvest stage, urease and catalase activities of soils were higher than transplanting stage, alkaline phosphatase activity under TF decreased clearly and that under the other treatments was increased to different degree. Bacteria and fungi quantities under TF were evidently increased over those under higher FWC for film mulching treatments. Actinomyete quantity of soil hadn't regular trend across all treatments. Moreover, Bacteria, fungi and actinomyete quantities weren't evident correlation with soil nutrient traits.In general, soil water content, weather and so on had much influence on the benefit of rice under plastic film mulching cultivaton. PM could promoted the N-metabolizing capacity and N absorbtion in rice plant and accumulation in grain. Moreover, under proper soil water content condition, the anti-stress protecting system should work effectively to defend the damage from oxidation. So, the rice under PM improved the rice growth to get sound yiled in company with high nutrient and water use efficiency. Therefore, in practical rice production, if only water and fertilizer management were proper according to local condition, rice yield was apt to increase with water and nutrient high-availability, which was very important to sustaining development of rice cultivation.