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tions at specified growth stages is the most common practice followed by the farmers (PhilRice, 1991;Pillai Low N use efficiency (NUE) continues to be a problem in the rice and Kundu, 1993).This does not consider the dynamic (Oryza sativa L.)-wheat (Triticum aestivum L.) cropping system. The leaf color chart (LCC)-based real-time N management can be crop N requirement and soil N supply because N recomused to optimize/synchronize N application with crop demand or to mendations were mainly derived from empirical testing improve existing fixed split N recommendations. We conducted a field of N response to few fixed doses. In fixed-time recomexperiment during 2001-2003 at Modipuram, India, to determine the mended N split schedule, the N splitting is skewed, the threshold LCC values for N application in rice and wheat, assess the first two splittings [one as basal at the time of planting/ need for basal N application, calibrate the LCC with a chlorophyll sowing and another at 25 to 30 d after transplanting meter (SPAD), and work out the economics of rice-wheat systems. (DAT) in rice and 21 to 25 d after sowing (DAS) in Treatments consisted of LCC scores of 2 to 5 for different cultivars wheat] occur at 21 to 30 DAS/DAT, and third dose is of rice and wheat and were compared with the zero-N control and a split at panicle initiation (PI) stage. In some rice-growrecommended fixed-time N splitting. In rice, LCC Յ 3 for 'Basmatiing countries, present recommendations call for 50 to 370', 4 for 'Saket-4', and 5 for 'Hybrid 6111/PHB-71' produced higher yield and NUE than recommended N splits. In wheat, maintenance and A.

Soil samples were obtained from a long-term trial conducted on a silty loam at Sardar Vallabhbhai Patel University of Agriculture & Technology, Modipuram (Meerut), in 2007-2008 to study the effects of various combinations of conventional and zero-tillage (ZT) and raised-bed systems on soil aggregation and associated organic C fractions in the 0-to 5-cm and 5-to 10-cm depth in a rice-wheat {Orysa sativa L-Triticum aestivum L.) rotation.Macroaggregates increased under a ZT rice (direct-seeded or transplanted) and wheat rotation with the 2-to 4-mm fraction greater than that of the 0.25-to 2-mm fraction. Bulk and aggregate associated C increased in ZT systems with greater accumulation in macroaggregates. The fine (0.053-0.25 mm) intra-a^regate particulate organic C (iPOM-C), in 0.25-to 2-mm aggregates, was also higher in ZT than conventional tillage. A higher amount of macroaggregates along with greater accumulation of particulate organic C indicates the potential of ZT for improving soil C over the long-term in rice-wheat rotation.

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Agricultural land degradation due to nutrient deficiencies is a threat to agricultural sustainability. As nutrients availability is influenced by soil heterogeneity, climatic conditions and anthropogenic activities; hence, delineation of nutrient management zones (MZs) based on spatial variability could be an effective management option at regional scale. Thus, the present study was carried out to delineate MZs in the Shiwalik Himalayan region of India by capturing spatial variability of soil properties and secondary and micronutrients status because of the emerging nutrient deficiencies. For the study, a total of 2575 geo‐referenced representative surface (0–15 cm depth) soil samples were collected from the study region covering an area of 53,483 km2. The soils were analysed for pH, electrical conductivity, soil organic carbon, available sulphur (S) and micronutrients (Zn, Fe, Cu, Mn, B and Mo) concentrations. There was a wide variation in soil properties with coefficient of variation values of 14 (for pH) to 86% for available Mo. Geostatistical analysis revealed spherical, Gaussian, exponential, stable, circular and K‐Bessel best‐fit models for soil properties. Most of the soil properties were having moderate spatial dependence except soil pH and S (strong spatial dependence) and Zn (weak spatial dependence). About 49%, 10%, 2%, 13%, 11%, 12% and 8% area of the study region were found to be deficient (including acute and marginal deficiency) in S, Zn, Fe, Cu, Mn, B and Mo, respectively. The principal component analysis and fuzzy c‐mean clustering were performed to develop the MZs. Four principal components with eigenvalues greater than 1 and accounting 65·4% of total variance were retained for further analysis. On the basis of fuzzy performance index and normalized classification entropy, four potential MZs were identified. Analysis of variance confirmed the heterogeneity in most of the studied soil properties among the MZs. The study indicated that the methodology of delineating MZs can be effectively used in site‐specific S and micronutrients management in the Shiwalik Himalayan region of India. Copyright © 2016 John Wiley & Sons, Ltd.