Some principles for the “Three Controls” nutrient management technology for irrigated rice
ZHONG Xu-hua,HUANG Nong-rong,ZHENG Hai-bo(Rice Research Institute of Guangdong Academy of Agricultural Sciences,Guangzhou 510640,China)
The"three controls" nutrient management(TCNM) is a new technology with which high and stable yield can be achieved with less fertilizer and pesticide input.Discussed in this paper are some principles of this new technology.(1)Fertilizer-N use efficiency(NUE) is negatively correlated with total N input and N rate at basal and/or at tillering stage.The NUE is greater when fertilizer-N is applied during panicle development and at heading than that applied as basal or at tillering.Therefore the amount of N applied as basal and/or at tillering should be reduced.(2)Tillering rate is determined quantitatively by the existing tiller number,leaf N concentration,and leaf area index.Higher productive tiller percentage(PTP) can be achieved either by reducing maximum tiller number or preventing existing tillers from death.The PTP is closely related with dry matter accumulation dynamics.Limiting dry matter production before panicle initiation is important for reducing maximum tiller number and hence achieving high PTP.(3) The occurrence and development of sheath blight is determined both by climatic factors and canopy indices,i.e.the maximum tiller number,leaf area index,leaf chlorophyll content,and light transmission ratio of the canopy at heading.Thus the disease incidence can be reduced through improved crop management.