Study On Resource Use Efficiency And Relative Advantage Of Productivity In Spring Maize-later Rice Planting Model On South China Paddy Field

The major objective of this study was for exploring the productive potentials in double rice cropping system in South China so as to ensure food security, deal with seasonal drought problems caused by global climate warming in South China, promote harmony development of the "grain crop-cash crop-feed crop" structure, enhance the comprehensive benefits in rice field productive system, accelerate sustainable, healthy and low carbon development of the agriculture as well as provide scientific accordance to strategic adjustment of the current rice field planting structure. This study was conducted under high yield cultivation conditions on a fixed field for 2 years with conventional double-rice cropping model (R-R) as check by a method of combination of soil with crop system. We discussed the annual productivity, resource use efficiency and nitrogen utilization characteristics in "spring maize-late rice" rotation pattern (M-R), analyzed the effect of background soil nitrogen supply on annual soil nutrient property and the dynamic changes in M-R planting pattern as well as the effects of different applied-N levels and tillage methods on yield formation of late rice in M-R cropping system. The main results were as follows:1. The experiments showed that M-R model had significantly advantages in annual productivity and resource use efficiency over the conventional R-R model. The annual yield and matter production efficiency in M-R model increased by 20.0% and 23.2%, respectively, compared to the traditional R-R planting model. And the annual soil resource use efficiency, the production efficiency of light, temperature, and water resources as well as radiation use efficiency (RUE) also increased by 9.75%,14.7%,20.4%,12.1% and 19.1%, respectively. Furthermore, the annual total output and the ratio of output/input increased by 16.7% and 8.04%, respectively. These results indicated that the M-R model was of higher yield, higher efficient and higher resource use efficiency.2. The results also showed that nitrogen fertilizer use efficiency in M-R planting model differed from that in R-R planting model. The M-R planting model was much better than R-R planting model in terms of nitrogen recovery efficiency (RE) and productive efficiency. The nitrogen recovery efficiency, whole nitrogen grain and matter production efficiency increased by 13.0%-23.0%,10.8%-12.6% and 12.7%-20.6%, respectively; the nitrogen harvest index (NHI) increased by 3.01%-3.98%; whereas the nitrogen partial factor productivity (PFP), agronomy use efficiency (AE) and physical utilization those of R-R planting model even these were not at significant level. 3. With same tillage method, compared to late rice of R-R planting model, the yield of late rice of M-R planting model increased by 2.13%-6.74%. The reasons for the yield increase were due to the increase of leaf area index (LAI), and the enhancement of the SPAD value and the effective PSⅡquantum yield (EQY) of flag leaf, the reduction of the non-photochemical quenching index (qN) after heading stage in M-R planting model, as well as the good performance of the photochemical utilization efficiency, which led to 3.7%-6.8%increase of the final total dry matter accumulation of M-R planting model at maturing stage. Moreover, compared with conventional tillage (CT) treatment, the yield of late rice under no-tillage(NT) treatment in M-R increased by 10.5%, which reached significant difference. The reasons for this yield increasing came from both the effective tiller number and spikelet number per unit area increases (by 8.53% and 6.77%, respectively); The yields of late rice in conventional tillage+ carbon(CTC) treatment, in conventional tillage+ straw-retuning to field(CTS) treatment under M-R planting model could be increased by 6.4% and 3.3%, respectively.4. There had no significant differences in soil total nutrient content including total N, total P and total K after late -season rice harvest between M-R cropping system and traditional R-R cropping system. However, the soil available K and available P contents got some improvements. Under conventional tillage method, the soil organic matter content after late rice harvest in M-R cropping system decreased by 4.44% coupled with the soil pH value lowering compared to the R-R cropping system. With no-tillage in straw-retuning to field and organism carbon application treatments, the soil organic matter content in M-R cropping system could be increased by 10.8%,3.41% and 44.4%, respectively.5. Compared with R-R planting pattern with the same N fertilizer rate, the yield of late rice in M-R planting patter increased by 2.41-6.32%. The reasons for increasing yield were due to the increases of grain number per hill and spikelets number per unit area. Also compared with R-R planting pattern during late growth stage (15 days after 80% heading), the leaf area index(LAI) of M-R planting patter was 1.34% to 17.5% higher; the SPAD value of flag leaf of M-R planting pattern,0.75% to 2.64% higher; the net photosynthetic rate (Pn)of flag leaf in M-R planting model,7.77% to 11.1% higher. Meanwhile, M-R planting pattern showed much better in terms of effective PS II quantum yield (EQY), electron transports rate (ETR) and coefficient of photo-chemical quenching (qP) which can reduce the coefficient of non-photochemical quenching (qN), and enhance the radiation use efficiency (RUE), and contributed the final total dry matter weight of M-R planting pattern to an increase of 1.64 to 4.42% over R-R planting pattern. 6. Compared with NoNo under low indigenous soil N-supply, the yield of later-season rice of the NoN treatment in M-R planting pattern increased significantly by 41.8% due to the effective panicle number per unit obviously increase by N-fertilizer application; the LAI and the SPAD value of flag leaf in the N0N treatment were 52.0% and 13.0% higher, respectively, during later growing stage; the net photosynthetic rate (Pn)of flag leaf of NoN treatment was 13.2% higher during later growth stage; the effective PSⅡquantum yield (EQY), electron transports rate (ETR) and coefficient of photo-chemical quenching (qP) which can reduce the coefficient of non-photochemical quenching (qN) showed strong advantage; the radiation use efficiency(RUE) was 4.49% higher. All these contributed to an increase of the final total dry matter accumulation of NON treatment at maturity stage to 21.2%, reaching significant difference. While under high indigenous soil N-supply, the yield of the late rice of NNM treatment in M-R planting pattern increased by 4.73% due to the effective panicle number increase and the spikelets increase per unit area.7. Under different indigenous soil N-supply for later -season rice, the total soil N content and organic matter content in M-R cropping pattern with same N-fertilizer application rate decreased by 1.4%-10.3% and 5.44%-10.5%, respectively, compared with R-R planting pattern. However, the soil pH value of M-R model was higher than that of R-R model. Under low indigenous soil N supply, the available soil nutrients including available N, available P and available K in M-R cropping system decreased by 4.65%, 13.7% and 3.04%, respectively, compared with traditional R-R planting model. However, with high indigenous soil N supply, the content of available N in M-R cropping pattern was 2.33% higher but 12.0% lower of the content of available K compared with R-R planting model. With zero N-fertilizer application to the 2 cropping seasons, the content of soil available N after later-season rice harvest in M-R cropping pattern was 9.30% lower than that R-R planting model, and N application to second cropping season could dramatically increase the soil organic matter and soil available N content, but decrease the soil available K content. With N-fertilizer application to 2 cropping seasons, the content of available N after later-season rice harvest in M-R cropping pattern increased by 2.50% compared with R-R planting model, and organic fertilizer application to the second season in M-R cropping pattern could enhance the soil organic matter and the total N contents, but decrease the soil available nutrient contents, especially for the soil available K content.8. During whole crop growing season in late rice field, the dynamic change tendency in soil nutrient contents appeared the same both in M-R and R-R planting system:soil pH value showed a tendency curve like "down-up-down"; the soil organic matter content showed a tendency curve like "down-up-stable finally"; the total nutrient content showed constant; with low indigenous soil N, the available soil nutrient content in M-R planting pattern showed a trend curve like "up-down "; with high indigenous soil N, the available soil K and available P in M-R planting pattern had the same tendency as with low soil N background; the available N content in M-R planting pattern showed a tendency curve like "down-up-down".