S.S. Bawa

Erodibility of Sandy Loam Aggregates in Relation to Their Size and Initial Moisture Content Under Different Land Uses in Semi-Arid Tropics of India

Soil erodibility, an index of ease of detachment of soil aggregates due to beating action of falling raindrops, is generally characterized through soil physical properties-based indices, which may not be applicable universally. The water stability of aggregates as determined by simple shaking under water though a more reliable index, does not simulate the actual field situation. The present study was conducted to determine the erodibility of natural, undisturbed soil aggregates from agricultural, forest, pasture, and eroded land uses from Punjab, India, in relation to their size and moisture status, using simulated raindrops in the laboratory. The mean EISRT (single raindrop technique-based erodibility index) was least under pastures followed by forest, agricultural, and eroded soils. The erodibility of aggregates increased significantly with an increase in aggregate size. Increasing the initial moisture content of aggregates resulted in increased erodibility with air-dry aggregates being the least erodible and the saturated ones the most. The effect of land use on soil erodibility was more pronounced when the aggregates were air-dried. The bigger (4.5 mm) raindrops did not differentiate the erodibility of aggregates from different land uses due to higher kinetic energy of the individual raindrops. The total number of raindrops used to completely disrupt an aggregate decreased with an increase in the size of raindrops. At saturation, even the aggregates from the pasture lands became unstable and their erodibility increased. Thus, the erodibility of bigger (> 10 mm) saturated aggregates was higher than the smaller saturated aggregates.

Combined effect of tillage and organic fertilization on soil quality key indicators and indices in alluvial soils of Indo-Gangetic Plains under rainfed maize–wheat system

Inceptisols in the submountainous region of Indo-Gangetic Plains in India are known as low productive areas due to several constraints like decline in soil organic matter and fertility, deterioration of soil physical and biological properties. The present study was conducted with tillage as main treatments and integrated nutrient management as subtreatments to improve soil quality and to identify the key indicators of soil quality after 5 years of experimentation in maize–wheat cropping system at Ballowal Saunkhri. Conventional tillage (CT) + interculture (IC) maintained significantly higher soil quality indices (SQI) of 1.12 which was at par with 50% CT + IC + chemical weed control (CWC) (1.08). Application of nitrogen (N) through 50% (organic) + 50% (inorganic) maintained higher soil quality with SQI of 1.10 followed by application of 100% N through organics (1.08). The results indicated that reduction in the intensity of tillage to 50% with interculture practices and combined use of organic and inorganic fertilizers maintained higher soil quality in these degraded Inceptisols. The methods of principal component analysis and computation of SQI adopted will be highly useful to future researchers, land managers, and students at locations across the world having similar climatic and edaphic conditions.

Effects of Conjunctive Nutrient Management on Soil Fertility and Overall Soil Quality Index in Submountainous Inceptisol Soils under Rainfed Maize (Zea mays L.)–Wheat (Triticum aestivum) System

The present long-term study was initiated to quantify the long-term effects of conjunctive nutrient management on soil quality, identify key indicators, and assess soil quality indices under a rainfed maize–wheat system in marginal Inceptisol soils in India. Results of the study revealed that soil organic carbon was significantly influenced by the conjunctive nutrient-management treatments. Among the nine treatments, the application of 100% recommended dose of nitrogen (RDN) (80 kg N ha−1), 15 kg N (compost) + 20 kg N ha−1 (inorganic), 25 kg N (compost), and 15 kg N (compost) + 10 kg N ha−1 (green leaf) resulted in greater organic carbon contents of 5.57, 5.32, 5.27, and 5.26 g kg−1, which were greater by 29.5%, 24%, 23%, and 22%, respectively, over the control. The greatest soil quality index (1.61) was observed with application of 25 kg nitrogen (N; compost) as well as with application of 15 kg N (compost) + 10 kg N ha−1 (green leaf). The order of percentage contribution of key indicators toward soil quality indices was available potassium (K) (34%) > available phosphorus (P) (32%) > available N (13%) > microbial biomass carbon (12%) > exchangeable calcium (Ca) (9%). The linear regression equation revealed the principal role of soil quality indicators in maize crop yield. The methodology and the results of the study could be of great relevance in improving and assessing soil quality not only for the study locations but also for other climatically and edaphically identical regions across the world.

Productivity, profitability and sustainability of rain-fed chickpea under inorganic and biofertilization in foothills of north-west Himalayas

A 4-year (2008–2009 to 2011–2012) study was conducted on the effect of mineral phosphorus (P) + sulphur (S) and biofertilizers on rain-fed chickpea (Cicer arietinum L.) at the Punjab Agricultural University’s Research Station, Ballowal Saunkhri, India. The experiment comprised of five combinations of P and S, viz. control (P0S0), no P + 10 kg S ha−1 (P0S10), 15 kg P + 10 kg S ha−1 (P15S10), no P + 20 kg S ha−1 (P0S20) and 30 kg P + 20 kg S ha−1 (P30S20); and three seed inoculation levels, viz. control, Rhizobium and phosphate-solubilizing bacteria (PSB), were laid out in randomized complete block design. Combined application of P + S resulted in improved growth, nodulation, yield attributes and yield. The increase in seed yield over control due to P + S ranged from 11.8% to 17.7%. Seed inoculation with Rhizobium recorded the highest growth, nodulation, yield attributes and yield of chickpea and was statistically at par with PSB and significantly better than no inoculation. Highest benefit/cost ratio (B:C, 2.19) was obtained in P30S20. In view of environmental pollution and high costs of chemical fertilizers, biofertilizers alone or in combination may help to achieve sustainable and ecological agricultural production.