Americas and Oceania Group - International Plant Nutrition Institute

Asia and Africa Group
South Asia
South India Region and Sri Lanka: Dr. T. Satyanarayana
Fertility Mapping through Spatial Variability in Rice Growing Soils of Cuddalore District, Tamil Nadu
Project Leader: V. Arunkumar, Scientist, Annamalai University Soil Science and Agricultural Chemistry, Chidambaram,
Tamil Nadu. E-mail: varrun1974@gmail.com
Project Cooperator: K.P. Ragunath
In this study, spatial variability maps were created on the GIS platform using soil fertility data of the
known sampled points and GPS readings of individual locations. These maps were then used to determine
the fertility status of unsampled farmer’s plots. Based on the predicted fertility, four management zones were
formed, viz., Zone I (Low N: Low P: High K), Zone II (Low N: Low P: Medium K), Zone III (Low N:
Medium P: High K), and Zone IV (Low N: Medium P: Medium K). On-farm experiments were conducted
during kharif 2011 taking rice as a test crop at 12 locations with three experiments in each management
zone. Fertilizer recommendations for yield targets of 5 and 6 t/ha generated in each management zone using
variability maps and DSSIFER (a computerized fertilizer recommendation system) were compared with
state government recommendations (150:50:50 kg/ha N:P 2 O 5 :K 2 O) and farmer practice (160:140:60 kg/ha
N:P 2 O 5 :K 2 O) across all the locations.
Nutrient application for a yield target of 6 t/ha resulted in an average rice yield of 6.2 t/ha (range 6 to 6.3
t/ha) across the management zones. Similar trend was observed for targeted yield of 5 t/ha with an average
yield of 5.2 t/ha. Thus, target yields were attained at all the experimental locations across the management
zones. Moreover, there was a statistically significant increase in grain yield with 6 t/ha yield target vis-a-vis
state recommendation (5.1 t/ha, 21%) and farmer practice (3.9 t/ha, 57%). In contrast, however, a significant
yield difference between targeted yield of 5 t/ha and state recommendation was noticed only at three of the
four management zones. Recommendations based on fertility maps resulted in a net return of INR 34,990/ha
with a benefit:cost ratio of 2.29 at a yield level of 6 t/ha. This return was INR 9,282/ha higher over the state
recommendation and INR 26,246/ha higher over farmer practice. These encouraging results notwithstanding,
there is a need to scale up the approach for larger areas. This project was completed in 2011. India-012
Site-Specific Nutrient Management for Chilli in Kalliyoor Panchayat of Kerala
Project Leader: C.R. Sudharmaidevi, Kerala Agricultural University Soil Science and Agricultural Chemistry
Department of SS&AC, Thiruvananthapuram, Kerala. E-mail: sudharmaidevi@yahoo.co.in
Project Cooperator: N. Saifudeen, Professor
The study was initiated after recognizing the decline in productivity of chillies in the experimental region
and the need to generate quantitative knowledge on efficient nutrient management strategy in chillies using
the principles of site-specific nutrient management (SSNM). Four representative chilli growing sites were
selected based on the variation in soil fertility. Nutrient omission plot studies were conducted to determine
the yield obtained from indigenous nutrient supply. Results from nutrient omission trials, initial survey
information and soil analysis data were considered to set yield targets of 12 and 16 t/ha. Field-specific
nutrient recommendations were developed using the relationship between yield and nutrient uptake at
multiple harvests, considering the indigenous nutrient supply, yield targets, and nutrient demand as a function
of the interactions between nutrients. On-farm trials were conducted to assess the recommendations generated
in this study which were compared with state recommendation and farmer practice.
Omission plot studies averaged over four locations indicated that NPK application (275-140-125) resulted
in 13.2 t/ha of chilli yield, which was 55% higher than obtained under farmer practice (80-55-25). Yields
obtained in plots omitting N, P, and K were 10.6, 13.0, and 10.9 t/ha, respectively, probably because of
high soil test P values. Averaged over three pickings, nutrient application for a yield target of 12 and 16 t/
ha resulted in a chilli yield of 11.8 and 17.3 t/ha. Higher yield in SSNM plots was possibly because of thrice
the number of fruits per plant in these plots than in farmer practice. Similarly, better quality fruits with
IPNI Interpretive Summaries 93