Declining pulse production has caused wide concern in recent years. A field experiment was conducted to investigate effects of balance fertilizers based on soil test values and targeted yield equations on soil biological activities, soil quality, nutrient acquisition and grain yield of lentil. Treatments included the use of farmyard manure (FYM), bio-inoculants and inorganic fertilizers at different rates and combinations. The results revealed significant improvement in nodulation, microbial counts, microbial biomass carbon (MBC), soil respiration, soil enzymes and soil organic carbon (SOC) with integrated approaches (i.e. fertilizer plus FYM or bio-inoculants); these improvements led to achievement of the specific target yield of 1.50 t/ha. Although the highest yield was achieved with fertilizers applied for a target yield of 2.0 t/ha, there was significant decline in nodulation, microbial counts, MBC, soil respiration, soil enzymes, SOC and soil quality. Correlation between soil quality index (SQI) and grain yield suggested a significant influence of balanced fertilization based on soil tests and target yield. Principal component analysis revealed the average contribution of soil quality indicators towards SQI was in descending order of SOC > acid phosphatase activity > total culturable fungi > available phosphorus > BMC, which are crucial for sustainable lentil production in alluvial soils.

A critical step in the quantification of soil quality (SQ) is the selection of SQ benchmarks. The benchmarks used in this study were SQ ratings made by 32 farmer collaborators representing a range of farming systems, scales of operation and geographic locations in the Mid-Atlantic region of USA. Soils from 45 pairs of sites identified by their farmers as having good and poor SQ were sampled over three seasons and analyzed for 19 soil parameters. Farmer judgments of SQ were based on many factors, most commonly soil organic matter, crop performance, soil water availability and erosion history. Selected individual soil parameters were normalized and integrated into an additive SQ index (SQI). Three additional indices were developed using discriminant analysis. The level of agreement between individual parameters, SQIs and farmer SQ ratings was evaluated using paired t-tests and mean percent difference values. The additive SQI was found to have the highest level of agreement with farmer SQ ratings (P<0.0001), demonstrating that a linear combination of soil parameters can be assembled that is more in agreement with holistic SQ criteria, such as farmer SQ ratings, than individual soil parameters. Extractable C from microwave (MW) sterilized soil (a measure of microbial biomass) was the individual parameter that best agreed with farmer SQ ratings (P<0.0001). Five additional soil C parameters, as well as aggregate stability, also agreed well with farmer SQ ratings (all P values <0.0005). The three parameters with the highest ratio of mean percent difference to coefficient of variation (an indication of parameter reliability) were extractable C from MW sterilized soil, anthrone reactive C and macroaggregate stability (14.2, 7.7 and 3.7, respectively). Mineral fertility parameters (pH, Ca, Ca:Mg ratio, P and K) were not significantly related to farmer SQ ratings (P values >0.05). The strong relationships observed between soil C parameters, soil structural parameters and farmer SQ ratings suggest that efforts to improve SQ in the study region should focus on monitoring and enhancement of soil C and soil structure.