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Estimating Indigenous Nutrient Supplies for Site-Specific Nutrient Management in Irrigated Rice

A. Dobermann^,*,a, C. Witt^a, S. Abdulrachman^b, H. C. Gines^c, R. Nagarajan^h, T. T. Son^d, P. S. Tan^e, G. H. Wang^f, N. V. Chien^d, V. T. K. Thoa^d, C. V. Phung^e, P. Stalin^g, P. Muthukrishnan^g, V. Ravi^h, M. Babu^h, G. C. Simbahan^a, M. A. A. Adviento^a and V. Bartolome^a

^a Int. Rice Res. Inst. (IRRI), DAPO Box 7777, Manila, Philippines
^b Res. Inst. for Rice (RIR), Sukamandi, Indonesia
^c Philippine Rice Res. Inst. (PhilRice), Maligaya, Nueva Ecija, Philippines
^d Natl. Inst. for Soils and Fert. (NISF), Hanoi, Vietnam
^e Cuu Long Delta Rice Res. Inst. (CLRRI), Omon, Cantho, Vietnam
^f Zhejiang Univ. (ZU), Hangzhou, P.R. China
^g Tamil Nadu Rice Res. Inst. (TNRRI), Aduthurai, Tamil Nadu, India
^h Soil and Water Manage. Res. Inst. (SWMRI), Thanjavar, Tamil Nadu, India

View larger version (36K): [in a new window]   Fig. 1. Relationships between soil tests and grain yield or nutrient uptake measured in N (0-N), P (0-P), and K (0-K) omission plots. Values shown are field averages of four successive rice crops grown from 1997 to 1999.

View larger version (57K): [in a new window]   Fig. 2. Relationships between plant nutrient accumulation and grain yield in N (0-N), P (0-P), and K (0-K) omission plots. Values shown are data of three to four consecutive rice crops grown from 1997 to 1999 in 155 farms at seven sites, including low- and high-yielding climatic seasons. INS, indigenous N supply; IKS, indigenous K supply; IPS, indigenous P supply.

View larger version (59K): [in a new window]   Fig. 3. Correlation between plant N accumulation in two types of paired N omission (0-N) plots in the same field. Unfertilized (-F) plots did not receive any fertilizer, whereas +PK plots received a full dose of P and K. Values shown are data of four consecutive rice crops sampled from 1994 to 1996.

View larger version (40K): [in a new window]   Fig. 4. Correlation between plant N accumulation measured in two N omission (0-N) plots within the same field. Values shown are data of three to four high-yielding seasons sampled from 1997 to 2000 in 155 farms at eight sites. The solid line shows the 1:1 line.

View larger version (44K): [in a new window]   Fig. 5. Precision of estimating the average indigenous nutrient supply in irrigated rice domains as a function of the number of farms and the number of years sampled. Contour lines show the relative error of estimating the domain mean (%) at three sites. All data are based on variance component analysis of grain yield measured in N (0-N), P (0-P), and K (0-K) omission plots in four (N) or two (P and K) high-yielding cropping seasons in each domain and assuming one omission plot per field.