Crop Yield Variability in Response to ENSO Phases

Mungari cotton, kharif sorghum; peanut/pigeonpea intercrop systems have been the major crops cultivated in Kurnool during the SW monsoon season. Sunflower, chickpea and post rainy season sorghum are the major sequential crops grown during post rainy (NE monsoon) season. We analyzed the distribution of crop yields for each ENSO phase.

Crop yields were grouped based on the categorization of ENSO phases (Table 17.1) since 1950 to 2002. These yields were calculated from observed crop production in each

Fig. 17.6. Seasonal rainfall distribution of Anantapur as affected by ENSO phase categories from 1963 to 2001

to 2001

Seasonal rainfall distribution of Nandyala as affected by ENSO phase categories from 1963

to 2001

Seasonal rainfall distribution of Nandyala as affected by ENSO phase categories from 1963

district. This analysis provides inferences on the performance and likely adaptability of a crop once the ENSO phase is known, based on historically observed yields in different ENSO phases.

Box plots of crop yield distribution in different ENSO phases (El Niño, La Niña, neutral) indicate yield distribution of 25th percentile from bottom of the box (light gray) and 75th percentile to the top of the box (dark gray), with a circle connected by horizontal line in the middle of the box representing median (50th percentile) of the crop yields time series. Bottom whisker cap indicates 10th and top whisker indicates

95th percentile of yield distribution. Horizontal lines with star or circle away from box plots are out-liers in the data representing a skewed distribution (Figs. 17.6 and 17.7).

In Kurnool, kharif sorghum median yield is above (0.75 t ha-1) during La Niña years, and distribution of sorghum yield in this phase ranged from 0.25 to 1.5 t ha-1 indicating that good rainfall distribution leads to higher yields in 50% of years and that sorghum yield in neutral years is also good compared to El Niño years (Fig. 17.8). Hence sorghum can be a rainy season crop option except in El Niño years. Contrary to expectations, mungari cotton yielded better in El Niño years compared to neutral or La Niña years, and can be a suitable crop option in El Niño years (Fig. 17.9). Peanut and pigeonpea intercrop system is an obvious choice in light soil areas of Kurnool during La Niña phase as the median yield for both the crops is conspicuously higher and yield addition in this phase is >250 kg ha-1 (Fig. 17.1oab). Chickpea and rabi sorghum have been two alternate crops for farmers of Kurnool as a sequential post rainy season crop, and both crops have different suitability options. While Chickpea yields were higher in El Niño years, its performance in La Niña is also consistently better than in neutral years (Fig. 17.11a). As opposed to this, sorghum median yields were higher and is a suitable option for this region in La Niña conditions (Fig. 17.11b).

Fig. 17.8. Rainy season sorghum yield as affected by rainfall in ENSO phases during 1950-2001 in Kurnool

Fig. 17.8. Rainy season sorghum yield as affected by rainfall in ENSO phases during 1950-2001 in Kurnool

Fig. 17.9. Mungari cotton yield as affected by rainfall in ENSO phases during 1950-2001 in Kurnool

Fig. 17.10. a Peanut yield with intercrop as affected by rainfall in ENSO phases during 1950-2001 in Kurnool; b intercrop pigeonpea yield as affected by rainfall in ENSO phases during 1950-2001 in Kurnool

All years El Miño La Niña Neutral ENSO phase

All years El Miño La Niña Meutral ENSO phase

All years El Miño La Niña Neutral ENSO phase

For Anantapur, ENSO phase wise crop yield analysis indicates that peanut/pigeonpea intercrop system (Fig. I7.i2ab) additive performance would be higher in La Niña years (>0.9 t ha-1), but in neutral and El Niño years its median yields are low (<0.7 t ha-1) and remain below district mean yields (Fig. 17.12).

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