Effects Of Localized Supply Of Water And Nitrogen On Physiology And Biochemistry Characteristic Of Maize

Agricultural water use still takes up a great proportion in water using in China. Food production mainly depends on irrigation. Efficient water use has become an important issue in recent years because the lack of available water resources is increasingly becoming a serious problem. Nowadays, China lacks of water resources, especially in arid and semi-arid areas northwest, so improving irrigation methods is the greatest potential to improve water use efficiency.Controlled alternate partial root-zone irrigation (CAPRI), also called partial root-zone drying (PRD) in other literature, is a new irrigation technique and may improve the water use efficiency in the indoor and field test in the arid and semi-arid areas. This new irrigation technique has broad application prospects in the development of water-saving agriculture. At the same time, the lack of soil fertility in the northern dry areas is also a serious problem, and the effect of fertilizer supply on improving crop production can not be ignored. It is ubiquitous in the world that low water and fertilizer use efficiency lead to the waste of resources and environmental pollution problems.The focus problem such as that how to give full play to crops own ability to adapt to the environment, that how to achieve high-efficient use of water and fertilizer, high-yield of crops, environmental protection, and that how to rationally irrigate and fertilize are taken into attention. Moreover, investigating crop conditions inherent physiological mechanism under different supply of irrigation and fertilization become the key problem.Therefore, this paper focuses on the effects of the crop protection enzyme activity and lipid peroxidation of maize on the local supply of water and nitrogen. At the same time, the physiology, growth and yield of maize were analysed in order to save water and fertilizer, to lay a foundation for formulating an high-efficient irrigation system, to provide a theoretical basis for the application of CAPRI technology in the arid and semi-arid areas.In this studay,(1) Plants were raised in split-root containers and irrigated on both halves of the container (conventional irrigation,CI),on one side only (fixed partial root zone irrigation,FPRI),or alternatively on both sides (alternate partial root zone irrigation,APRI);The intimidated intensities included: mild stress(soil moisture was 60±5% of field capacity),moderate stress (soil moisture was 50±5% of field capacity)and severe stress (soil moisture was 40±5% of field capacity).the effect of different irrigation methods on physiological and biochemical response, dry biomass and WUE of maize to drought and rehabilitation of water was studied.(2)The design in the field experiment consisted of three fertilization methods:①fertilized on both sides of the row (Conventional fertilization,CF),②on one side only (fixed partial root zone fertilization,FPRF),③alternatively on both sides (alternate partial root zone fertilization,APRF)and three levels of fertilization amount: high level, moderate level and low level。Physiological and biochemical response of maize leaf, plant height, stalk diameter, N uptake in seeds and stalk, 100-seed weight and yield were measured. The main results as follows:1. In the FPRI conditions, the MDA content of corn leaves and on both sides of roots are all significantly increased than CI in three intimidated intensities; In the APRI conditions, compared with the CI, MDA content of leaves has mo change , in mild and moderate stress, MDA of root has no significant difference ,but in severe stress, decreased significantly. After rewatering, the MDA of leaves and roots are obviously reduced in APRI conditions; In the FPRI conditions, however, MDA of leaves and roots of non-irrigated zone remained relatively high level, little changed the irrigation district root. These indicate that APRI can significantly reduce the harm of activated oxygen, but FPRI increased damage of lipid peroxidation role to the crop.2. During drought,root SOD activity increased significantly in non-irrigated zone of FPRI, had no change in irrigated zone of FPRI and dry zone of APRI, reduced in wet zone of APRI when compared to that of CI. After rewatering,SOD activity in the non-irrigated zone of FPRI were enhanced markedly, and in the irrigated zone of FPRI was similar to that of CI, but that in both root zones of APRI was decreased significantly as compared to CI. Leaf SOD activity, during drought and after rewatering, had no significant difference among 3 irrigation methods. The change of POD activity was different: leaf POD activity of APRI was much higher then that of FPRI and CI in moderate stress. In the mild and moderate stress, there was no significant difference among 3 irrigation methods; For the mild and moderate stress, there was a significantly increase in the irrigated zone of FPRI and APRI, while a decrease or no significant difference occurred to the non-irrigated zones when compared to CI. After rewatering, for leaf, there was no significant difference among 3 irrigation methods when mild stress; In moderate stress ,leaf POD activity of APRI was similar to that of CI .leaf POD activity of APRI and CI were significantly higher than that of FPRI; But when severe stress, a marked increase occurred to leaf POD activity of APRI as compared to that of FPRI ,and decrease significantly compared to that of CI.For root, FPRI increased POD activity in the irrigated zone significantly while caused no effect on that in the non-irrigated zone when compared to CI. As for APRI, no significant difference when mild and moderate stress but a marked increase when severe stress occurred to POD activity in both root zones as compared to CI. In view of the fact that SOD and POD are inducing enzyme, and POD express in the early stage, it can be speculate that whether in drought or normal supply conditions, active oxygen damage to crop increase when fixed irrigate compared to CI. However, active oxygen damage decreased when fixed irrigation.3. During drought and 12 hours after rewatering, Leaf relative water content of APRI has a increase or no significant difference and that of FPRI has a decrease or no significant difference when compared to CI. After rewatering, Leaf proline of APRI and FPRI and root proline of APRI are significantly higher than that of CI; compared to CI, FPRI increased proline content in the irrigated zone significantly while caused no effect on that in the non-irrigated zone when mild stress; It has no difference in the irrigated zone and decrease in the non-irrigated zone when moderate and severe stress.This further illustrates that the use of APRI is conducive to raising crops osmotic adjustment ability, enhancing water retaining capacity, thereby improving crop water use efficiency.4. For the three fertilization methods, MDA content decreased with the increase of nitrogen, POD activity significantly enhanced with the amount of nitrogen increased. Maize leaf MDA increased significantly for FPRF treatment but decreased for APRF treatment when compared to that of CF treatment. POD activity of APRF was obviously higher than that of CF. As for high N level, increased significantly, but there were no significant differences under low and medium N levels compared to that of CF. Thus, regardless of which fertigation, increasing use of nitrogen can increase crop resistance of the ability of oxygen free radicals, lessen membrane damage, and this effect of the application of nitrogen fertilizer is different because of the amount of fertilizer and the different methods. Generally speaking, APRF is superior to FPRF and CF.5. The effect of different fertilization methods and amount of fertilization on crop growth showed that the effect of fertilization on the plant height indicated in the latter stage, and there is no significant difference among the3 fertilization methods;Maize stem diameter increase with the increase of the fertilization, localized fertilization methods are conducive to the growth of stem diameter, especially in the most obvious APRF.Stem N uptake is not significant in 3 fertilization methods, seed and the total nitrogen uptake of APRF significantly increased, there was no difference in the FPRF when compared to that of CF. For 100_seed weight was significantly enhanced for APRF under all three fertilization levels but for FPRF only under high level when compared to that of CF.Both two methods of localized supply of nitrogen increased significantly maize yield when compared with that of CF and the increase for APRF was more significant. Thus, a partial application of nitrogen fertilizer can be realized to reduce the volume of fertilizer without affecting or even increase crop yields, especially the APRF was more increase significantly.