Response of Hybrid Castor Under Different Fertility Gradient: Correlation Between Castor Yield and Normalized Difference Vegetation Index (NDVI) Under Inductive Cum Targeted Yield Model on an Alfisol

ABSTRACT

Precision application of nutrient based on soil test value is important for improving nutrient use efficiency and yield of hybrid castor. Field trial was conducted during 2021 at Tapioca and Castor Research Station, Yethapur, Salem District, Tamil Nadu, India (110${ }^{\circ }$35’ N, 780${ }^{\circ }$ 29’ E). Fertilizer prescription equations (FPEs) were developed for hybrid castor by adopting inductive cum targeted yield model approach under irrigated condition on Alfisol. Initially, soil fertility gradients were established with respect to soil available N, P and K nutrients, and 24 treatments were imposed in three fertility strips under factorial randomized design. Principle component analysis revealed that all the variables accounted for developing the FPEs of hybrid castor are present at the positive quadrant which mean that all the variables are highly important toward the castor seed yield production. From the field experimental data, the basic parameters [nutrient requirement (NR) and nutrients contributions from farmyard manure (Co), fertilizer (Cf), and soil (Cs)] were computed. The nutrient required for producing one quintal of hybrid castor seed yield was evaluated as 3.20 kg of nitrogen, 1.23 kg of phosphorus pentoxide (P₂O₅), and 3.28 kg of potassium oxide (K₂O). The study revealed that soil nutrient contribution was high in case of available phosphorus (41.87%), available nitrogen (21.56%), and available potassium (19.12%), respectively, toward P, N, and K nutrient uptake by hybrid castor. The nutrient contribution from farmyard manure (Co) toward the total uptake was 21.40% of N, 10.35% of P₂O₅, and 26.06% of K₂O, respectively. FPEs for hybrid castor and a ready reckoner of fertilizer dosages were developed using basic data for operational range of soil test values for intended yield target under inorganic fertilization alone and Integrated plant Nutrient System (IPNS) (NPK and FYM).

KEYWORDS:

• Fertilizer prescription equations
• hybrid castor
• NDVI
• nutrient requirement
• precision agriculture

Acknowledgements

The help and cooperation of scientists at All India Co-ordination Research Programme on Soil Test Crop-Response (AICRP-STCR), TNAU, Coimbatore, India in taking up the field experiment and analyzing field data are gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.