| The study was conducted to determine the development of above-ground and under-ground biomass, soil water and salt transport regularity, effect of soil water and salt transport regularity on development of above-ground biomass and root distribution in drip irrigation under mulch on saline-alkaline land at Agriculture Ecology Engineering Station of Gansu Agricultural University during crops grow season of 2005 and 2006, different irrigation treatments (maize: high irrigation (4875 m3/hm2),medium irrigation (4275 m3/hm2),low irrigation (3750 m3/hm2);cherry tomato: high irrigation (5426 m3/hm2),medium irrigation (4419 m3/hm2),low irrigation(3700 m3/hm2) and different salt supply levels (maize: high salt supply (0.998%),medium salt supply (0.978%),low salt supply(0.958%);the same salt level (0.958% ) was supplied for cherry tomato) were employed in column and field experiments, maize and cherry tomato as an indicator crops. The results are followed:1. Evaporation and salt upper movement were reduced, formed 20– 40 cm light salinity root area, which is good for crop growth, indicated that drip irrigation under mulch had a effective of washing desalinization, especial on saline-alkaline land.2. Soil water moisture was affected by amount of drip irrigation, evaporation and water absorption of root. Mulch reduced evaporation of surface soil layer, the growth state and distribution of root was influenced by soil water content and soil fertilization, the affect of soil water content on deep root growth was evidence.3.Salt supply level was same, in different irrigation treatments, the highest soil moisture level (19.76%) was reached 60-100 cm soil layer at maize emerging stage; at maize jointing stage, the highest soil moisture level (11.42%) was reached 40-600 cm soil layer. Irrigation was same, in different salt supply levels treatments, the highest soil moisture level (19.36%) was reached 40-60 cm soil layer at maize different growth stages.The maize experiment indicated that maize production can be obtained on saline-alkaline land with soil salt level under 0.998%, amount of irrigation (4275 m3/hm2) was optimum management for maize production in similar experimental conditions.4. Salt supply level was same, in different irrigation treatments, the highest soil moisture level was reached 60-100 cm,40-60cm and 60-100cm soil layer under high irrigation, medium irrigation and low irrigation treatments respectively, there values were at 20.47%, 21.29% and 20.07% related to corresponding irrigation treatments, at different cherry tomato growth stages. The highest soil moisture level (21.06%) was reached 60-100 cm soil layer at cherry tomato emerging stage; at flowering and fruit-bearing stage, the highest soil moisture level (24.04%) was reached 20-40 cm soil layer. In horizontal direction, the soil water content was decreased with distance from drip sprinkler, soil moisture (9.58%) in 55 cm was reached the highest level. The cherry tomato experiment indicated that cherry tomato production can be obtained on saline-alkaline land with soil salt level under 0.958%, amount of irrigation (4419 m3/hm2) was optimum management for cherry tomato in similar experimental conditions.5. Salt supply level was same and irrigation was different, the leaching depth of Cl-, SO42-, and Na+ were increased with irrigation. At maize emerging stage, the highest Cl- content (0.386 g./kg ) was reached 60-100 cm soil layer, the highest SO42- content (1.332 g./kg ) was reached 40-60cm cm soil layer; at maize jointing stage, the highest level of Cl- content and SO42- content was reached 40-60cm cm soil layer. At different maize growth stages, the highest Na+ content (4.21 g./kg ) was reached 20-40cm soil layer. Irrigation was same and salt supply level was different, at maize emerging stage, the highest levels of Cl- content (0.389 g./kg ), SO42-content (0.517 g./kg ), Na+ content (1.766 g./kg ) was reached 60-100 cm soil layer; at maize jointing stage, the highest levels of Cl- content (0.863 g/kg),SO42- content (0.833 g/kg) and Na+ content (1.766 g/kg) were reached at 40-60cm soil layer. Medium irrigation treatment has higher effect of salt leaching than high irrigation treatment and low irrigation treatment. It indicated that main roof grow within 40 cm soil layer, salt leaching below 40 cm soil layer after medium irrigation, medium irrigation treatment can reduce salt toxicity to plant root, leading higher maize production.6. Salt supply level was same and irrigation was different, the highest Cl- content (0.199 g./kg ) was reached 40-60 cm soil layer, the highest SO42- content (1.22 g./kg ) and the highest Ca2+ content (0.96 g./kg ) was reached 60-100cm cm soil layer. At cherry tomato emerging stage, the highest levels of Cl- content, SO42- content and Ca2+ was reached about 60cm soil layer; at flowering and fruit-bearing stage, the highest levels of Cl- content and SO42- content was reached 40-60cm soil layer. Medium irrigation treatment can reduce salt toxicity to plant root, leading higher cherry tomato production.7. The experiment was showed the root of maize and cherry tomato was decreased with amount of irrigation, the depth of root distribution in high irrigation was shallower than in low irrigation. About 85 % of dry maize root weight was distributed within 0-60cm soil layer, the root length and dry root weight was highest at maize heeding stage; about 75 % of dry cherry tomato root weight was distributed within 0-20cm soil layer, the root length and dry root weight was highest at cherry tomato flowering and fruit-bearing stage. The root extinction coefficient was also showed similar results. 8. The grow tendency of canopy biomass of maize and cherry tomato with growth date is"S"curve, the equation is cubic curve. The grow tendency of fruit yield of cherry tomato biomass with growth date is"Unimodal type"curve, the equation is cubic curve.9. Drip irrigation under mulch was best management in semiarid area of Northwest of China. Drip irrigation under mulch had higher water use efficiency (WUE) than traditional furrow irrigation, the more WUE increase was 69.34%, 141.27% and 144.81 in high irrigation treatment, medium irrigation treatment and low irrigation treatment than in traditional furrow irrigation, respectively. After economical evaluation, the medium irrigation treatment (4419 m3/hm2) had higher evaluated parameters than high irrigation treatment and low irrigation treatment. Drip irrigation under mulch was best choice on saline-alkaline land with salt under 0.958%, medium irrigation treatment obtained the highest fruit yield for cherry tomato in semiarid area of Northwest of China.
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