Crop Productivity And Resource Use Efficiency Under Conservation Tillage In A Dry Land Spring Wheat-field Pea Rotation System

To introduce conservation tillage into western Loess Plateau, the applicability of conservation tillage for Loess soil regarding crop productivity, the effects of conservation tillage on soil conditions and resource use efficiency under the local semi-arid conditions, and underlying mechanism of yield effects of conservation tillage need to be studied. To address these issues an experiment on different conservation tillage systems was designed for a one-year one-crop rotation of spring wheat and field pea, and implemented from August, 2001 to 2005 in Dingxi, a typical semi-arid area on the western Loess Plateau. Six different tillage system were involved in the experiment, they are: conventional tillage (T); no-till without stubble (NT); conventional tillage with stubble incorporated (TS); no-till with stubble retention (NTS); conventional tillage with plastic film mulch (TP) and no-till with plastic film mulch (NTP). Main aims of this thesis are: 1) to analyze different conservation tillage effects on soil temperature and soil water; 2) to explore harmony of soil water and temperature to provide a better growing environment for crops; 3) to analyze different conservation tillage effects on crops productivity and its underlying mechanism; 4) to analyze water use efficiency, nitrogen use efficiency and profitability of crops production under different tillage systems.Field experiments in 2001-2005 showed that:7) NTS improved the rotation grain yield significantly while no-till without stubble retention had the worst grain yield compare to conventional tillage system. The average yield of field pea under NTS was 14%, 24%, 17%, 5% and 9% higher than T, NT, TS, TP and NTP respectively. The average yield of spring wheat under NTS has 16%, 26%, 14%, 3% and 6% of yield advantage than T, NT, TS, TP and NTP respectively. The average system yield of NTS within 2rotation cycles has 16%, 25%, 15%, 4% and 7% of system yield advantage than T, NT, TS, TP and NTP respectively.8) Stubble retained on the no-tilled soil surface did decrease soil temperature at the profile of 0-25cm at 14:00 in wheat growing season, but, this soil temperature decrease didn't delay or/and reduce wheat emergence, germination and crop yield obviously. Average soil temperature at the profile of 0-25cm at 14:00 was 0.9°C, 1.1°C, 1.0°C, 0.3°C, 0.3°C and 0.6°C lower than that of T, NT, TS, TP and NTP respectively, probably because that heat fluxes was reduced under residue mulch thus resulting in lower soil temperatures. But, wheat growing was even better under NTS, so this soil temperature decrease under NTS won't impede its adoption.9) Water stored in surface layers is more available for crops than that of deeper layers, surface (0-10cm) soil water content under no-till with stubble retention was greatly improved up to 90% compare to conventional tillage, no big difference among different treatments'water storage at 0-200cm, but, more water is available for crops and crops are able to extract more water from the soil under no-till with stubble retention. Average water storage of T, NT, TS,...