Effect of fertilizer application based on soil test crop response approach on active and passive pools of soil organic matter in maize-wheat cropping system

A long-term fertilizer experiment was initiated in kharif 2007 in a maize-wheat sequence at the Experimental Farm of Department of Soil Science, Chaudhary Sarwan Kumar Himachal Pradesh Krishi Vishvavidyalaya, Palampur under the network of All India Coordinated Research Project on Soil Test Crop Response (STCR) Correlation Studies. The experiment consisted of eight treatments (control, general recommended dose, soil test based, farmers' practice, target yield of 25 (rabi)/30 (kharif) and 35 (rabi)/40 (kharif) q ha(-1) either with or without 5 t ha(-1) farm yard manure) replicated thrice in a randomized block design. All the passive and active pools of soil organic matter (SOM) were highest under STCR treatments for target yield 35 q ha(-1) + farmyard manure (FYM). The highest value of both humic and fulvic acids under STCR treatment for target yield 35 q ha(-1) with FYM was statistically at par with treatment for target yield 25 q ha(-1) with FYM. The R-2 value indicated that about 96% to 98% of the total variation in grain yield was attributable to SOM fractions. The contribution of all fractions of SOM towards the total variation in straw yield was 96% to 97%.