《葡萄栽培学英文资料：lecture 1 irrigation》由会员分享，可在线阅读，更多相关《葡萄栽培学英文资料：lecture 1 irrigation（40页珍藏版）》请在金锄头文库上搜索。
1、Lecture 1 plant water relations and soil moisture At the end of this lecture you should be able to: recall the meaning and significance of various terms and units of measure used to describe water loss and levels of soil moisture e.g. evapotranspiration Describe a range of methods/approaches to dete
2、rmine soil moisture status and explain the principles involved Describe a range of methods/approaches to determine Et and crop Et and explain the principles involved Describe and explain the principles of water budgeting and keeping a water balance4/2/2015MMB - WINE 201-20141Introduction - water is
3、unique as substance indispensable for plant life. Plants absorp H2O, translocate H2O, metabolise with H2O, transpire H2O. constituent of all cells, varying in % composition - in living growing tissue may be as much as 80 - 95% a solvent - provides medium for compound transfer through the plant. prov
4、ides turgor - tugor pressure acts as mechm for plant & tissue support. 1/3 of many CHOs & proteins include chemically combined H2O within CHO/protein molecules. 4/2/2015MMB - WINE 201-20142water constraints A continuing net loss of H2O from plants can Close stomata cause growth to stop Cause loss of
5、 structural integrity (wilt) Cause a final irreversible change in plant body & metabolism - result in death. Some plants grow where H2O is scarce - may have mechanisms & physiological processes to assist survival & reproduction.4/2/2015MMB - WINE 201-20143Transpiration and photosynthesis4/2/2015MMB
6、- WINE 201-20144transpiration & evaporation plants loose H2O from aerial tissues by evaporation termed transpiration (main source of transpiration loss - thru leaf stomata) The soil looses H2O by evaporation from the soil surface. combined loss from plant and soil termed evapotranspiration term norm
7、ally applied to the plant & the area of soil beneath the leaf canopy. 4/2/2015MMB - WINE 201-20145Soil moisture1.Soil moisture as a source of water for plant growth, 2.Methods for measuring soil moisture4/2/2015MMB - WINE 201-20146H2O resources for crop plant growth most H2O absorption thru roots. s
8、oil moisture primary source of H2O for crop plants. Soil moisture reservoir may be added to by rainfall, other precipitation events, H2O overflow from other areas & irrign reservoir depleted by Drainage and run off, Evaporation from plant and soil, organisms other than the crop plants drawing on the
9、 reservoir. 4/2/2015MMB - WINE 201-20147descriptn of soil moisture content include max soil moisture content field capacity - FC, min level for plant growth permanent wilting point - PWP. diff between the 2 levels is the available moisture content -AMC (or AWC). value of AMC can be calculated for 1.
10、 soil as a whole or2. volume of soil occupied by the plant (determined by depth and radial spread of plant roots). (note: latter more useful)4/2/2015MMB - WINE 201-20148Measuring soil moisture determine soil moisture level to assure selves that plant can obtain water to replace transpiration loss am
11、ount of H2O in soil can be measured in many ways (1) directly and (2) indirectly. workers use a range of units of measure - Cos of approach direct or indirect measures of water present different soil moisture properties being measured - differences with use/non use of SI units. eg. Typically soil H2
12、O amount described by tension measurement values potential energy measurement values. 4/2/2015MMB - WINE 201-20149Measuring water potentialFree water has -1. a low tension, 2. Free water can move freely in the soil, -3. Therefore free water can be said to have high potential energy.Convention - soil
13、 H2O potential is written ysoil. 4/2/2015MMB - WINE 201-201410y.= psiunits of measurement Some of the units of measurement used to relate H2O quantity include - Bars, mm of mercury, mms of water, kilopascals, Binding force (Pf). Value for free H2O set at 0 bars (benchmarking convention). values for
14、remaining soil H2O - after some H2O has been lost - stated in negve bars.4/2/2015MMB - WINE 201-201411Direct determination of soil moisture1. Gravimetric determination of soil moisture Lab determination most accurate direct way to determine H2O content record wt difference between wet & dry soil.2.
15、Soil feel A practical determinatn but of limited accuracy. Janick cites descriptns of hand held soil sample condition for a med -fine textured soil (sandy loam?) relates “feel” to % field capacity (see upcoming slide)4/2/2015MMB - WINE 201-201412Soil feel of med -fine textured soil with varying % H2
16、O content soil condition % field capacity With firm pressure some water can be squeezed from a ball of soil - 100 + Forms a durable pliable ball. If pressed firmly some will stick to the thumb - 75 - 100% Forms a ball that will remain intact when tossed, sticks slightly under pressure - 50 - 75% Forms a ball but will crumble with a few tosses - 25 - 50% Crumbly, will not form a ball - below 25%4/2/2015MMB - WINE 201-201413Moisture content, soil types and water potential values4/2/2015MMB - WINE
