| It is difficult to cultivate paddy rice in conventional waterlogged condition in a high position of field or a place where water resource is deficient, due to the terrain of red soil regions being mainly low hill and hillock in the south China. Here, seasonal drought is very serious because of the uneven distribution of the rainfall. The popularly accepted cultivation of paddy rice variety in aerobic soil condition is very useful in development of rice cultivation in the low hill area of southern part of China. Almost the same yield of rice grain could be obtained in aerobic as in waterlogged cultivation and furthermore 60%~100% of irrigated water can be saved. However, phosphorus availability is becoming a more serious problem since the shift of waterlogged to aerobic. Therefore, it is of great importance to investigate the effect of soil water content on the transformation of soil phosphorus in this new rice cultivation system. In this paper, we are trying to clarify the interaction between soil water and phosphorus and its effect on phosphorus nutrition of rice plant and thus, provide an appropriate way to manage the water and phosphorus in the system of rice cultivation in aerobic soil condition in the red soil area.Field, pot and incubation experiments were conducted to study the effect of soil water and phosphorus (P) supply on paddy rice cultivated in aerobic soil. The results obtained were as follows.1. The results in the field experiment indicated that soil water and P had remarkable effect on the leaves' area and the interaction of soil moisture and P was significant. Rice leaf emergency was the fastest at moderate water (80% of saturated water content, SWC) and moderate P (26.5kg/hm2). There was also a remarkably interactive effect of water and phosphorus on the valid radiation of photosynthesis (VRP) and the VRP values were enhanced with the increase of P application rates and soil moistures.Net photosynthesis velocity (NPV) was also affected but interaction was small. No significant effect was found in the air vent conducting degree (AVCD) and rising velocity (RS), but the interaction was distinct. The transpiration of paddy rice cultivated in aerobic soil was slight, which was useful for saving water. The greatest transpiration took place when the soil moisture was high. To some extent, P application in soil had effect on NPVR, NPV and AVCD. Moderate or high moisture regime could produce higher dry matter of paddy rice and increasing yield and enhancement of P application rates could improve the transpiration of rice leaves.2. Soil water and P application had an interactive effect on rice biomass and grain yield, the biggest effect being in grains followed by shoots and roots. When soil moisture was 60% of SWC, biomass and grain yield of the rice were significantly reduced. No difference of the biomass and grain yield was found when soil moisture was at 80% and 100% of SWC. The biomass and grain yield of rice cultivated in aerobic soil increased with the increase of P application rates. More P fertilization should be done in aerobic cultivation to get good yield of rice grain than in waterlogged cultivation.3. Soil moisture had no significant effect on phosphorus uptake while phosphorus application had asignificant effect. In pot experiment, phosphorus uptake in grain was the largest at soil moisture of 80% of SWC but the average of total phosphorus uptake was in the order of shoots > grains > roots; in field experiment, the order was grains > shoots > roots. In field experiment, amount of phosphorus uptake by the rice plant was ordered by moderate moisture > high moisture > low moisture. When moisture was at 80% of SWC, phosphorus uptake by the rice plant increased with the increase of P application rates. It was important to maintain a good soil moisture condition if rice is to be cultivated in aerobic soil.4. Soil moisture and P had no significant effect on total P (TP) and organic P (OP) in soil but on available P (AP). After planting (or incubating) paddy rice, soil OP content i...
|
PDF Full Text Request