| Mechanical transplanting of rice seedlings has become prevalent in Jiangsu province. The combination of mechanical transplanting of rice seedling and full amount of wheat straw residue incorporation into the soil has become a recommended practice for rice cultivation in Jiangsu province recently. Rice seedlings prepared for mechanical transplanting usually are younger in seedling age, nursed at higher seeding density and weaker in seedling quality, tended to suffer severer mechanical damage, leading to slower rooting and recovery growth in later stage. The situation becomes gravely worse when combined with full amount of wheat straw residue incorporation into soil. Traditionally, the paddy field are prepared after flood tillage harrowing, ploughing and steeping, consequentially the plough layer is usually suspended like a plasma. When employing mechanical transplantation, the rice seedling is inclined to be planted overly deep. The poor soil water permeability leads to bad rooting conditions, delayed tiller growth and poor population quality. Simplified paddy field preparation such as ploughing and raking without flooding water is a helpful practice to alleviate this issue. However, it is not well understood how the impact of combining all wheat straw residue incorporation into soil with the aforementioned practice on the rice plant growth, yield formation, source-sink properties, material production and distribution, nutrient uptake, rice grain quality and soil properties per se. For clarifying these issues, this study aimed at combination of mechanical transplanting and all wheat straw residue incorporation into soil in production season of 2014-2015. The rice variety employed was Zhendao99, a medium season medium maturity japonica rice. The agronomic traits investigated includes tiller dynamics, yield and its components, source-sink relationship, dry matter production and distribution, nutrient uptake, root, rice grain quality and soil characteristics. The influence of dry paddy field preparation and flooded paddy field soil preparation was also compared. This study will provide support information and understanding to mechanical transplanting of rice seedling in high-yield cultivation. The main results were as follows:1. The tiller population dynamics showed some inconsistency between the two experimental years. In 2014, the tiller number increased rapidly during the first 30 days after transplanting, tiller rate slowed down slightly before reaching the maximum tiller number stage, and the tiller diminish rate was low after the maximum tiller number stage. The maximum number of tiller was slightly less in dry prepared field than that of flood prepared field, yet the panicle number was 9.19% more than that of flood prepared field. In 2015 production season, tiller rate was always higher in dry prepared field than that of flood prepared field, with a significant difference at 30 days after transplanting as well as the maximum tiller number. The eventual panicle number was 9.43% more in dry prepared field than that of flood prepared field.2. As to the yield and yield components, theoretical yield and actual yield of dry prepared field were all higher than flood prepared field, with increment of 8.36%,6.27% in 2014 and 2015 respectively. When reviewing by yield components, dry prepared soil achieved more panicles (10.45%) than flood prepared field, whereas the grain number per panicle decreased by 5.75%. The full-filled grain percentage was 4.74% higher in dry prepared field. The differences in 1000-grain weight from plants between dry prepared field and flood prepared field were negligible.3. On the aspect of source-sink relationship, plants from dry prepared field possessed slightly smaller LAI at early growth stage, but it was compensated by a higher LAI at heading stage and grain filling stage by 7.47% and 6.38% respectively. In middle and later period, photosynthetic area increased significantly. Practice of dry prepared field showed limited effect on sink capacity per unit area.4. As to the dry matter production and distribution, the total dry matter production at heading and maturity stage from dry prepared field were slightly heavier than those from flood prepared field. Translocation and redistribution of dry matter accumulated in leaf, stem and sheath were higher for plants in dry prepared field, and panicle dry matter accumulation was greater in dry prepared field as well. Consequentially, the economic coefficient was higher in dry prepared field.5. As to the root system, the rice plants from dry prepared field grew more adventitious root per plant, possessed higher root weight. This may facilitate the tiller growth, slow down the leaf senescence and prolong the photosynthesis activity in later growth stage.6. As to the nitrogen absorption and utilization, the plant nitrogen content showed no difference at heading and maturity between fields prepared differently. But the total plant nitrogen uptake at heading and maturity stage from dry prepared field were more than those from flood prepared field. The nitrogen translocated from leaf, stem and sheath, and nitrogen accumulated in panicles were all higher in dry prepared field than those from flood prepared field. Apparently, this field preparation practice improved the nitrogen grain production efficiency and nitrogen harvest index.7. As to the rice grain quality of rice, (1) The brown rice rate, polished rice rate and complete polished rice rate were higher in dry prepared field than those from flood prepared field, with the latter showed bigger difference; (2)The field preparation exhibited limited effects on chalky grain rate, chalkiness and length-width ratio of rice; (3) The amylose and protein content of rice grain in dry prepared field were lower than those from flood prepared field (nearly to be significant), but gel consistency was higher than these of water soil preparation; (4) From the point of the RVA of rice starch viscosity, the highest viscosity, thermal plasma viscosity and the values of disintegration from dry prepared field were bigger than those of flood prepared field, but the value of cut and the gelatinization temperature were lower in the comparison. These changes may contribute to the improvement of the eating quality; (5) Field preparation method exerted no obvious effect on macro mineral element concentrations, except that Mn and K content were lower, Cu, Zn, Ca, Mg and P were higher in the rice grain from dry prepared field compared with those of flood prepared field.8. As to the soil properties, dry prepared field showed reduced water content, and increased soil redox potential. However, most of the time during rice growing season, the surface soil bulk density was slightly higher in dry prepared field. In general, dry prepared field possessed a significantly improved soil permeability.9. As to the production cost and profit, transplanting costed 4.5?6 yuan less per mu in dry prepared field (at an average of 5.25 yuan), increased grain yield added up another 87.87? 117.92 yuan profit per mu (at an average of 102.9 yuan), totally increased profit was up to 108.1 yuan per mu. |
PDF Full Text Request