Introduction 1. URGENCY OF THEMES Water is reducing on the volume as well as the quality in most area in the world. For agricultural water, the volume of water is reduced due to critical competition of the other economic which using water. Irrigational water-saving to raise the index of agricultural products per unit of irrigational water which became extremely important. Therefore, “research reveal the influence of irrigated-agriculture to reduce volume of water, reduce consumption volume of water for rice in Ha Nam area” is very urgent now. 2. OBJECTIVES OF THEMES - Research on impact of irrigated agriculture to Shallow –open- dried irrigation to reduce consumption water in order to establish the scientific basis and practic to establish irrigational procedure . 3. RESEARCH METHOD - Inheritance: based on some research results, appling to achieve objective of the project. - Primary analysis: deperiodining the impact of Shallow –open- dried irrigation to rainfall as scientific basis for formulating the process of water-saving. - Field experimenl: to test theoretical research results. - Statistical analysis: to handle the experimental results 4. SCOPE OF RESEARCH The research was conducted within the general theory about the impact of Shallow–open-dried irrigation, the level of reserves and irrigation, the volume of irrigation for the region of Ha Nam Province. Theoretical research is conducted on a database of 24 years (1985- 2008), experimental research was conducted in 4 harvest season (2 1 winter season and 2 summer season) to demonstrate for results of theoretical research. 5. MEANING OF SCIENCE AND PRACTICE OF THEMES • Meaning of science - Establishing a scientific basis of influence between the irrigational formula and water reserve levels to the levels of irrigational water and the level of season’s irrigation. - Establishing the scientific basis of the relationship between effective rainfall and actual rainfall in Ha Nam. • Practical Meaning - Specified the potential to reduce the level of irrigation, irrigational water is very large when apply Shallow–open-dried irrigation regimes combined Reserve 100mm. - Developing software to calculate water-saving regime for rice with two basic importation on calculating volume of rain-water in efficiency and ETO when dry field. 6. NEW CONTRIBUTIONS OF THESIS - Theme showed potential of reducing volume of irrigational water, it is reduced greatly if applied Shallow –open-dried irrigation regime and reserve rain-water to 100mm without reducing output of rice. - Theme showed that there is no close correlation between actual rainfall and effective rainfall in the south of Ha Nam. 7. STRUCTURE OF THE THESIS The thesis is presented in four main chapters, comprised 149 pages, 32 tables, 59 figures, 62 references. 2 Chapter I Overview OF the impact of Shallow open-– dried to volume of water, volume of Consumption 1.1 Overview of water regime on surface of field and main processes in rice-soil Under the influence of water regime on the surface of field, occured process in rice-soil very diverse. Those processs includes: changes of dynamics of reduction-oxidation reaction (Eh) changes of acid of soil (pH) change of mechanical properties, status of exist of nutrition in the soil and the relationship between reducing output and irrigation regime. In the soil, reducing reduction-oxidation reaction (Eh) depends on the time and nature of submerged land and fertilizer regime. Besides the dependence on these factors, Eh also depends on rice. In the soil For pH, when the soil with value of pH > 7, the process of full water, pH is decreased gradually and approach to value = 7. When the soil with value pH <7, due to the weak phase so pH increases and gradually and approach to value = 7. time of Flood is long so, pH is increasing on the value. The metabolism of nutrients in the soil plays a very important for the tree. When soil change the phase from anaerobic (flooded) to Aerobic (dried), Chemical reactions in soil occured according to direction of oxidation. The nutrients in soluble regime, good for rice develops. 1.2 Overview of relationship between the lack of water to rice’s output Theoretical and experimental researchs, practical of agricultural production shown, the regime of surface water directly affects to the 3 productivity of rice. In general, when dehydrated, evaporation of reduction affects to rice’s output. 1.3 Overview of effective rainfall in the world 1.3.1 Overview of effective rainfall in the world In the World had many research on volume of effective rainfall that was announced. Which notably: • Research of the United State’s land protect organization: Po = P(125 - 0,2P)/125; when P < 250 mm; Po = 125 - 0,1P; when P > 250 mm. in there: Po is the efficiency rainfall, P is the actual rainfall. • Russian’s researchs: with P ≤ E + (W dr - W o ) take α = 1, with P > E + (W dr - W o ) take α = [E + (Wdr - W o )] / P. Among them: P is the actual rainfall, E is actual evaporation; Wdr is surface water layer at the end of period; W o is a surface water layer at the the first of period; α is rainfall using Coefficient. • Research of China: for P < 5 mm, take α = 0; for 5 mm < P < 50 mm, take α = 0,8 ÷ 1; for P > 50 mm, take α = 0,7 ÷ 0,8. • Programmer of CROPWAT: offer 4 open Plan. Plan 1: P hq = % P Plan 2: P hq = 0,6*P - 10 (for P < 70 mm) P hq = 0,8*P - 24 (for P > 70 mm). 4 Plan 3: P hq = a*P - b (for P < z mm), P hq = c*P - d (for P > z mm). Coefficient a, b, c, d and z are confirmed by user. Plan 4: P hq = P/125 (125 - 0,2*P) for P < 250 mm, P hq = 125 + 0,1*P for P > 250 mm. 1.3.2 Effective rain research in Vietnam Nguyen Duc Chau (2001) [7] on the basis of experimental material in Tuy Phuoc district - Binh Dinh in 1998 ÷ 2000 shown using coefficient of rainfall reached from C = 0.57 - 0.7. 1.3.3 Comments - The research results in-home and out-home shown that efficiency closely depended on research area. - Most of research results in home only stop at results of experiment that were not provide the way to period line effective rainfall from the actual rainfall. 1.4. Overview of research for water saving irrigation of rice in the world The reduction of water through contributing surface water layers proved very effective. Notably, research in many countries as Japan, China, Philippines, India, Spain, America etc. shown that if reasonable regulation can reduce in maximum on the water from 20% to 45% compared with continuously flooded irrigation, output is not reduced. 1.5 Overview of water saving research for rice in Vietnam Within the system, researchs [8] [15] [18] shown that it is possible to save the water from 5 to 10%. On the surface of field, Some researchs [11] showed that volume of water for irrigation fluctuates quite large. In formulars of 5 Shallow –open-dried irrigation, dried time of field is many, the rainfall using coefficient is increased 1.6 Shapter’s conclution • In the surface of neutrality-soils, applicating field dried mode, process occured in the soil is good for rice. Includes: - Eh up, harmful substances such as Fe2 +, CO2, organic acids, H2S is reduced. - Increasing oxygen in the soil, beneficial to the development of roots. - Strengthening activities of beneficial bacteria in the root zone of rice. • Although rice are very sensitive with the lack of water. but if apply appropriate irrigation regime will not reduce output of rice. • Rice is hygroscopic plant but if in full-water field is also limited growth, so reducing output. • On the surface of field, both basic research and applications, results showed is fairly good. But in Vietnam, so far, no research of any research announces on the impact of Shallow –open-dried regime to reducing water in seasons in rainy condition and detail of operational management regimes. • Affects of the Shallow –open-dried irrigation regime to lose volume of water is also not mentioned in the published research. This is also a problem need to detail in this thesis. 6 Chapter II RESEARCH on rule of rainwater distribution and affecting to effective rainfall, volume of water, Consumed WATER 2.1 Research on rule of distribution volume of rain-water by the time of the research area 2.1.1 Some characteristics on research area Ha Nan is located the south of Hanoi, extend from 20 0 34'18'' to 21 0 18'26'' in the north latitude, 105 0 17'18'' to 106 0 0’28'' in the east longitude, including 1 city and 5 districts with a total area of 85,958 hectares, population of 785,057 people. Irrigation system is almost by dynamic. 2.1.2 Distributional rule of rainfall in the research area Analyzing rain documents of Phu Ly station within 24 years (1985-2008), results showed that: the distributional rule of rain on (Table 2-1) with precipitation> 50mm got large proportion (60% for spring and 82% for harvest season), it is disadvantage for increasing using coefficient of rainfall. Table 2-1: Rules on the average rainfall distribution at Phu Ly station Unit: % TT Season X ≤ 20mm 20<X≤50 mm 50<X≤ 100mm X> 100 mm 1 spring 16,6 23,9 44,5 15 2 harvest 5,8 12,2 55,6 26,4 7 2.2 Effect of rain distribution rules to efficiency of rainfall under the current irrigation regime 2.2.1 Scientific basis From equation: Xhq j = (a j - a j-1 ) + ET j + S j - m j (2-1) with: Xhq j = X j - DR j in there: Xhq j is a effective rainfall in period from j-1 to j, X j is a actual rainfall in period from j-1 to j, DR j is a consumption rainfall in period from j-1 to j, a j , a j-1 is a surface water layer at period j and j-1, ET j is lose evaporation at period from j-1 to j, S j : is a lose by impregnated in long time in period from j-1 to j, On base of equation (2-1), with formulas NTX (a j =30-50mm), NLLT (a j =0-50mm), or NLP (a j = 0-50mm), effective rainfall is period by SWI software. 2.2.2 Research the relationship between rainfall and effective rainfall according to the actual irrigation 2.2.2.1 The relationship between effective rainfall and actual rainfall by rainstorm Based on actual rainfall distribution into 3 groups: with X tr ≤ 20mm; 20 mm< X tr ≤ 50mm; and X tr > 50 mm. Results of analysis has over 3000 rainstorms within 24 years of 2 spring and autumn in Ha Nam showed that , excluded group with X tr ≤ 20mm (R 2 > 0,9), remaining groups related to effective and actual rainfall (R 2 < 0,5). 2.2.2.2 The relationship between effective rainfall and actual rainfall by month Except some months in the spring season with rainfall is a correlation from average to closely (R 2 = 0,5 -:- 0,98), remaining months are not tightly correlated (Table 2-2a,b). 8 Table 2-2a. The statistical parameter relations X tt and X hq statistic of spring reason in Ha Nam Month Regression equation Number of example Correlation coefficient R 2 I X hq = 0,23 X tt + 8,4 24 0,49 II X hq = 0,73 X tt + 3,7 24 0,97 III X hq = 0,46 X tt + 12,2 24 0,76 IV X hq = 0,24 X tt + 15,6 24 0,5 Table 2-2b. Statistical parameters with correlation X tt và X hq parameters of rain reason in Ha Nam. Month Regression equation Number of example Correlation coefficient R 2 VI X hq = 0,125 X tt + 41,2 24 0,24 VII X hq = 0,164 X tt + 79,8 24 0,48 VIII X hq = 0,2 X tt + 74,6 24 0,36 IX X hq = 0,25 X tt + 53 24 0,48 X X hq = 0,042X tt + 10,1 24 0,1 2.2.3 The relationship between effective rainfall and actual rainfall according to reason Analysis Results on the relationship between effective and actual rainfall showed that this relationship is less close in both Spring harvest reasons (R 2 = 0,32 -:- 0,41) ( Table 2-2c). Table 2-2c. Statistical parameters with correlation X tt và X hq reasons system in Ha Nam reason Regression equation Number of example Correlation coefficient R 2 Spring X hq = 0,173 X tt + 152 24 0,32 harvest X hq = 0,141 X tt + 207 24 0,41 9 2.3 Effects of rainfall distribution rule to the volume of irrigation water under the current regime results of correlation analysis between rainfall and irrigational water levels in the Ha Nam's system showed there is no correlation between these two quantities (R 2 = 0,04 -:- 0,05). 2.4 Influence of actual rainfall to irrigational water Analysis Results of correlation between rainfall and irrigational water showed a closed correlation (R 2 > 0,9) (Table 2-2d). Table 2-2d: statistical parameters related to the actual rainfall X tt and irrigational water DR and reason system in Ha Nam Reason Regression equation Number of example Correlation coefficient R 2 Spring DR = 0,823 X tt - 150 24 0,91 Harvest DR = 0,856 X tt - 203 24 0,96 2.5 Conclusions of chapter -Rainfall in Ha Nan with rainstorms > 20mm predominant absolute on total volume (83% for spring reason and 94% for harvest season). So if the formula is applied irrigation NTX (30-50mm), will not take advantage of rainfall which satisfies with the water regime of the rice. So the rainfall and necessary volume of water is high. - Although in some cases with correlation coefficient is very closed (rain under time with X tt ≤ 20mm; rain under month with X th < 30mm) but in general, -Correlation between the actual rainfall and effective rainfall of the remain cases are not closed. Therefore, there is no scientific basis to establish the relationship between the actual rainfall and effective rainfall on the system of Ha Nam. 10 [...]... On base of soluting equation (3-1), the rainfall and rainfall in zone under Ha Nam province within 24 years according to different equation of irrigation are period by WSI software 3.1.2 Research on effects of irrigational formula to potential of reducing the volume of Consumption water and the rainfall for rice field in Ha Nam province On the basis of meteorological data for weather stations in Phu... tSTAT ≤ t(α/2)(n-1): allowed to concludes that 2 statistical samples is not different with statistical meaning p= α 3.2.2 Content of experimental arrangement Placement of experiment in Liem Tiet, Thanh Liem, Ha Nam Experiment time from the Harvest reason in 2005 to Spring Season in 2007 Experiments with 10 cells, size 1.5 x 1.5 m with 9 watering formula Layout cells following experiments: - Cell No 1:... formula combines NLP reserves 100mm This is the basis for selection regimes in irrigated fields to reduce water, reducing consumption water for irrigation in Ha Nam province 2) The potential for irrigation to reduce the average area of Ha Nam for the service (if applicable rate reserve formula and NLP 100 mm) can be reduced by 40% for the irrigation service and over 55% for Spring reason 3) The potential... if Appling minimize Shallow 26 –open-dried combined with rain water reserve This is a basis for selection regimes in irrigated fields to reduce water, reduce consumption water in Ha Nam province Potential of rainfall in Ha Nam in average for all reason are (if Appling formula of Shallow–open-dried and level of reserve with 100 mm) can achieve 40% irrigational level for Spring reason and over 55% for... from October 20th onwards Based on meteorological data, volume of water of 3 irrigational formulas: NTX, NLLT and NLP with 3 reserve mode (50mm, 100mm, 150mm), of the season of spring and harvest in Ha Nam within 24 years (1985-2008) , is period The analytical results show a closely related between the levels of irrigation and irrigation formula of productional increasing Highest level at the formula... volume of field 3.1 The theory of effects of Shallow–open-dried irrigation to the rainfall, irrigational volume of rice fields 3.1.1 Basis to determine the volume of water and the rainfall to rice in Ha Nam To determine the rainfall mj and volume of Consumption DRj needing to solute the equation (3-1a) with conditions required (3-1b,c,d) includes: aj = mj + aj-1 - ETJ - Sj + (Xj - DRj) (3-1a) amin ≤ aj . p= α. 3.2.2 Content of experimental arrangement Placement of experiment in Liem Tiet, Thanh Liem, Ha Nam. Experiment time from the Harvest reason in 2005 to Spring Season in 2007. Experiments. reduce water, reducing consumption water for irrigation in Ha Nam province. 2) The potential for irrigation to reduce the average area of Ha Nam for the service (if applicable rate reserve formula. Establishing the scientific basis of the relationship between effective rainfall and actual rainfall in Ha Nam. • Practical Meaning - Specified the potential to reduce the level of irrigation, irrigational