Americas and Oceania Group - International Plant Nutrition Institute

Fruit yield variograms of different sampling scale showed that predicted yield levels within the orchard
remained similar for 10 and 20 m grid sizes, but varied significantly at the 40 m grid size at Nong Khrah. In
Umsaitning, fruit yields remained unchanged up to the 40 m grid, but changed abruptly at 60 m. This suggest
that 20 m grid size is appropriate sampling scale in locations with greater topographical variations in terms of
frequent piedmont (slope) and pediment (valley) variations, while the 40 m grid sampling density is sufficient
where such variations are low. This was well highlighted in the fruit yield variograms where larger grid sizes
often predicted erroneous fruit yield zones as compared to the ground truth data. Similar observations were
found while interpreting variograms for pH, organic carbon as well as available macro and micronutrients.
Variograms of soil test values at a 20 m grid sampling density were superimposed along with fruit yield
variograms and distinct classes of soil properties were found for different yield zones within the orchards
studied. This information will be used for developing SSNM recommendations for the different yield zones
within the orchard. Similar studies will be done in Maharashtra and Madhya Pradesh. India-003 v
86 IPNI Interpretive Summaries