Overview of research for water saving irrigation of rice in the world The reduction of water through contributing surface waterlayers proved very effective.. in there: Xhqj is a effectiv
Trang 11 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 productsper 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 dried irrigation to reduce consumption water in order to establish thescientific basis and practic to establish irrigational procedure
–open-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 theimpact of Shallow–open-dried irrigation, the level of reserves andirrigation, 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
Trang 2winter season and 2 summer season) to demonstrate for results oftheoretical research
5 MEANING OF SCIENCE AND PRACTICE OF THEMES
Meaning of science
- Establishing a scientific basis of influence between theirrigational formula and water reserve levels to the levels of irrigationalwater and the level of season’s irrigation
- Establishing the scientific basis of the relationship betweeneffective 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-driedirrigation regimes combined Reserve 100mm
- Developing software to calculate water-saving regime for ricewith two basic importation on calculating volume of rain-water inefficiency and ETO when dry field
6 NEW CONTRIBUTIONS OF THESIS
- Theme showed potential of reducing volume of irrigationalwater, it is reduced greatly if applied Shallow –open-dried irrigationregime and reserve rain-water to 100mm without reducing output ofrice
- Theme showed that there is no close correlation betweenactual rainfall and effective rainfall in the south of Ha Nam
7 STRUCTURE OF THE THESIS
The thesis is presented in four main chapters, comprised 149pages, 32 tables, 59 figures, 62 references
Trang 3Chapter I Overview OF the impact of Shallow–open-dried
to volume of water, volume of Consumption1.1 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 ofacid of soil (pH) change of mechanical properties, status of exist ofnutrition in the soil and the relationship between reducing output andirrigation regime
In the soil, reducing reduction-oxidation reaction (Eh) depends
on the time and nature of submerged land and fertilizer regime Besidesthe dependence on these factors, Eh also depends on rice
In the soil For pH, when the soil with value of pH > 7, theprocess 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 pHincreases 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 importantfor the tree When soil change the phase from anaerobic (flooded) toAerobic (dried), Chemical reactions in soil occured according todirection of oxidation The nutrients in soluble regime, good for ricedevelops
1.2 Overview of relationship between the lack of water to rice’s output
Theoretical and experimental researchs, practical of agriculturalproduction shown, the regime of surface water directly affects to the
Trang 4productivity of rice In general, when dehydrated, evaporation ofreduction 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 rainfallthat was announced Which notably:
Research of the United State’s land protect organization:
is surface water layer at the end of period; Wo is a surface water layer atthe the first of period; α is rainfall using Coefficient
Trang 5Phq = c*P - d (for P > z mm).
Coefficient a, b, c, d and z are confirmed by user
Plan 4: Phq = P/125 (125 - 0,2*P) for P < 250 mm,
Phq = 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 experimentalmaterial in Tuy Phuoc district - Binh Dinh in 1998 2000 shownusing coefficient of rainfall reached from C = 0.57 - 0.7
1.4 Overview of research for water saving irrigation of rice in the world
The reduction of water through contributing surface waterlayers proved very effective Notably, research in many countries asJapan, China, Philippines, India, Spain, America etc shown that ifreasonable regulation can reduce in maximum on the water from 20% to45% compared with continuously flooded irrigation, output is notreduced
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 thatvolume of water for irrigation fluctuates quite large In formulars of
Trang 6Shallow –open-dried irrigation, dried time of field is many, the rainfallusing coefficient is increased
- 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 applyappropriate irrigation regime will not reduce output of rice
Rice is hygroscopic plant but if in full-water field is also limitedgrowth, so reducing output
On the surface of field, both basic research and applications, resultsshowed is fairly good But in Vietnam, so far, no research of any researchannounces on the impact of Shallow –open-dried regime to reducing water inseasons in rainy condition and detail of operational management regimes
Affects of the Shallow –open-dried irrigation regime to losevolume of water is also not mentioned in the published research This is also
a problem need to detail in this thesis
Trang 7Chapter 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 200 34'18'' to
210 18'26'' in the north latitude, 1050 17'18'' to 1060 0’28'' in the eastlongitude, including 1 city and 5 districts with a total area of 85,958hectares, population of 785,057 people Irrigation system is almost bydynamic
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% forspring and 82% for harvest season), it is disadvantage for increasingusing coefficient of rainfall
Table 2-1: Rules on the average rainfall distribution at Phu Lystation
Unit: %
20mm
20<X≤50mm
50<X≤
100mm
X> 100mm
Trang 8in there: Xhqj is a effective rainfall in period from j-1 to j, Xj is
a actual rainfall in period from j-1 to j, DRj is a consumption rainfall inperiod from j-1 to j, aj, aj-1 is a surface water layer at period j and j-1,
ETj is lose evaporation at period from j-1 to j, Sj: is a lose byimpregnated in long time in period from j-1 to j,
On base of equation (2-1), with formulas NTX (aj =30-50mm),NLLT (aj =0-50mm), or NLP (aj = 0-50mm), effective rainfall is period
2.2.2.2 The relationship between effective rainfall and actual rainfall by month
Trang 9Except some months in the spring season with rainfall is acorrelation from average to closely (R2 = 0,5 -:- 0,98), remainingmonths are not tightly correlated (Table 2-2a,b).
Table 2-2a The statistical parameter relations Xtt and Xhq
statistic of spring reason in Ha Nam
Month Regression equation Numberof
Table 2-2b Statistical parameters with correlation Xtt và Xhq
parameters of rain reason in Ha Nam
Month Regression equation
Numberofexample
Table 2-2c Statistical parameters with correlation Xtt và Xhq
reasons system in Ha Nam
reason Regression equation Number Correlation coefficient
Trang 102.4 Influence of actual rainfall to irrigational water
Analysis Results of correlation between rainfall and irrigationalwater showed a closed correlation (R2 > 0,9) (Table 2-2d)
Table 2-2d: statistical parameters related to the actual rainfall
Xtt and irrigational water DR and reason system in Ha Nam
Reason Regression equation
Numberofexample
- Although in some cases with correlation coefficient is veryclosed (rain under time with Xtt ≤ 20mm; rain under month with Xth <30mm) but in general,
Trang 11-Correlation between the actual rainfall and effective rainfall ofthe remain cases are not closed Therefore, there is no scientific basis toestablish the relationship between the actual rainfall and effectiverainfall on the system of Ha Nam
- Analysis of the distribution of rain by time under total ofvolume, results showed that rate of rain by time with 20mm<X≤100mmreached high rate This rate reached about 78% rainfall by reason inspring reason and 92,6% rainfall by reason in harvest reason Rain withrainfall > 100mm only reached about 26,4% rainfall in harvest reasonand reached 15% rainfall in Spring reason This is meaning indetermine the volume of water containing in reasons
Trang 12Chapter III research on the effects OF Shallow –open- dried irrigation AND volume of reserve to
irrigational 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)
In there : t is one time of irrigation, ∆t is time of stop between 2time of irrigation, Xj is a actual average rainfall which pour out on totalarea of irrigation, DRj is a average Consumption rainfall on total area ofirrigation DRj is period base on basis of surface water layer at caculatedtime Detail as follows:
DRj = Xj khi Wj-1 >= amax + areserve;
DRj = Xj – (amax + areserve – Wj-1) khi Wj-1 < amax + areserve;
DRj = 0 khi Xj – (amax + areserve – Wj-1) got a nagetive value
In case of sowing by order, average values etj, Sj, Xj và DRj areajusted by multiply with coefficient K as follows:
K = j/tg khi j < tg,
K = 1 khi tg < j < tst,
K = 1 – j/(tst+tg) khi tst < j < (tst+tg)
Trang 13In there : tg is time to sow, tst is growth time,
On base of soluting equation (3-1), the rainfall and rainfall in zoneunder Ha Nam province within 24 years according to different equation ofirrigation 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
Ly Level of irrigation throught years at the face of field corresponds tothe irrigational formula NTX, NLLT, NLP and the level of reserves(50mm, 100mm, 150mm), is identified by WSI software Results asfollows
3.1.2.1 Influence of irrigational formula and volume of reserve to to potential of reducong the level of irrigation
Spring's season start on 15th to February 28th, harvests fromMay 20th onwards Autumn's season sows start on 15th to June 30th,harvests 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 andharvest 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 Highestlevel at the formula NTX in two the season of spring and harvest (andaverage 5612 m3/hectare and 4206 m3/hectare) In NLLT formula, theaverage of irrigational level in 24 years in Spring reason with 4514m3/hectare (down 19.6% compared with NTX) to 2875 m3/hectare ofharvest season (down 31.6% compared with NTX) In Shallow –open-dried formula, the average irrigational level about 3926 m3/hectare (forSpring, down 30% compared with NTX) and 2583 m3/hectare (harvestreason downs 38.6% compared with NTX)
Trang 14Regarding the relationship between depth of water reserve andlevel of irrigation: if the depth of water storega is high so irrigationallevel is low Reduction of water level(compared to reserve 50mm)received in the depth of 100 mm and 150 mm respectively with 21% to24% (for Spring) and 43% to 53% (for harvest).
0 500 1,000 2,000 3,000 4,000
Spring reason Harvest reason
Figure 3-3c: Influence of depth of reserve water layer to the irrigationallevel
3.1.2.2 Influence of irrigational formula and the depth of water reserve
to potential of reducing the volume of Consumption water
There is a closely related between the rainfall water andformula of production increase, between the rainfall water and the depth
of rain water reserve, the volume of Consumption water is reduced fromformula of agricultural irrigation inregular, Shallow–open-Continues toShallow–open-dried The level of Reducing irrigational water reachedabout 23% of the harvest reason and about 29% to 30% of spring reasonrespective with Shallow–open-Continues and Shallow –open-driedformulas
For the relationship between the depth of rain water reserve andvolume of Consumption water, results showed that reduction ofConsumption water between different depths are very different Thedifference between the reserve with 50mm and 100mm are very large,this difference reached 35% to 70% In contrast, the difference betweenreserve with 100mm and 150 mm is not much Between these two