Vertical Assessment of Soil Quality In Permanent Manurial Experiment of Dryland Ecosystem, Tamil Nadu, India

A study was conducted to assess the impact of different nutrient management practices on soil quality in a permanent manurial experiment cotton field established in 1982 at the Agriculture Research Station of the Tamil Nadu Agricultural University, which falls under the dryland ecosystem of Kovilpatti in Tamil Nadu, India. The experiment was carried out in a randomized block design with nine different treatments. The effect of these treatments in different depths (0–15, 15–30 and 30–45 cm) was compared, and the soil quality index was developed with a total of 27 parameters, including physical, chemical and biological parameters. Principal component analysis was carried out and the principal components with eigenvalue >1 were selected to determine the indicators to be retained in the minimum data­set. The highly weighted variables, viz. field capacity, available water content, cation exchange capacity, nitrogen, phosphorus, potassium, calcium, magnesium, etc. with a variance of 93.57% were retained for MDS. Linear scoring functions were used to transform them into unitless scores ranging from 0 to 1. Three different methods of soil quality were analysed, viz. weighed additive soil quality index (SQI_w), additive soil quality index (SQI_a) and Nemoro soil quality index (SQI_n). In all three methods, the treatment receiving farmyard manure at 12.5 t ha^–1 showed superiority in maintaining soil quality