Balanced and integrated use of organic and inorganic fertilizers may enhance the accumulation of soil organic matter and improves soil physical properties. A field experiment having randomized complete block design with four replications was conducted for 36 years at Punjab Agricultural University (PAU), Ludhiana, India to assess the effects of inorganic fertilizers and farmyard manure (FYM) on soil organic carbon (SOC), soil physical properties and crop yields in a maize (Zea mays)-wheat (Triticum aestivum) rotation. Soil fertility management treatments included were non-treated control, 100% N, 50% NPK, 100% NP, 100% NPK, 150% NPK, 100% NPK + Zn, 100% NPK + W, 100% NPK (-S) and 100% NPK + FYM. Soil pH, bulk density (BD), electrical conductivity (EC), cation exchange capacity, aggregate mean weight diameter (MWD) and infiltration were measured 36 years after the initiation of experiment. Cumulative infiltration, infiltration rate and aggregate MWD were greater with integrated use of FYM along with 100% NPK compared to non-treated control. No significant differences were obtained among fertilizer treatments for BD and EC. The SOC pool was the lowest in control at 7.3 Mg ha and crop yields were positively correlated with SOC. Continuous cropping and integrated use of organic and inorganic fertilizers increased soil C sequestration and crop yields. Balanced application of NPK fertilizers with FYM was best option for higher crop yields in maize-wheat rotation.

blanket recommendations for fertilizer N are used (Adhikari et al., 1999). Overapplication of N in cereal crops leads to low N recovery effi-When N application is not synchronized with crop ciency and risk of NO 3 pollution of ground water. The chlorophyll demand, N losses from the soil-plant system are large, meter, also known as SPAD meter, is a simple, portable diagnostic leading to low N fertilizer use efficiency. Peng and Casstool for identifying crop N status. We used it to test need-based N management approaches for rice (Oryza sativa L.) and wheat (Triti-821

blanket recommendations for fertilizer N are used (Adhikari et al., 1999). Overapplication of N in cereal crops leads to low N recovery effi-When N application is not synchronized with crop ciency and risk of NO 3 pollution of ground water. The chlorophyll demand, N losses from the soil-plant system are large, meter, also known as SPAD meter, is a simple, portable diagnostic leading to low N fertilizer use efficiency. Peng and Casstool for identifying crop N status. We used it to test need-based N management approaches for rice (Oryza sativa L.) and wheat (Triti-man (1998) demonstrated that RE of topdressed urea cum aestivum L.) on a loamy sand in northwestern India. Applying during panicle initiation stage could be as high as 78%. 30 kg N ha Ϫ1 each time the SPAD value fell below the critical value Hence, plant need-based application of N is crucial for of 37.5 resulted in application of 90 kg N ha Ϫ1 , which produced rice achieving high yield and N use efficiency. Soil tests for yields equivalent to those with 120 kg N ha Ϫ1 applied in three splits. N fertilizer recommendations in flooded rice soils have Using a SPAD value of 35 was inadequate for the two rice cultivars not been successful (Stalin et al., 1996; Adhikari et al., because it resulted in application of only 60 kg N ha Ϫ1 and, thus, low 1999). The chlorophyll meter (SPAD-502, Minolta, Ramyields. With high inherent soil fertility resulting in rice yield of Ͼ3 sey, NJ), also known as SPAD (soil plant analysis devel-Mg ha Ϫ1 in zero-N plots, applying N basally or a week after rice opment) meter, can quickly and reliably assess the N transplanting did not further increase yield. Limited experimentation status of a crop based on leaf area. It has been success-821

A survey of the DTPA-extractable Cu levels of approximately 1000 fields representing a large number of soil types in Saskatchewan suggested that, under current cropping systems, Cu deficiencies appear to be concentrated in the Grey Soil Zone. They are especially probable in seven soil associations, which include light Transition of Grey and Brownish-Grey Podzolic soils. Soil criteria for detecting Cu deficiencies in cereal crops cannot be fully documented using conventional calibration tests and techniques. However, data from 21 field trials and a growth chamber study indicated that the critical level of DTPA-extractable Cu in these soils is approximately 0.4 mg∙kg−1 for cereals. Large spatial variability of DTPA-extractable Cu levels has been found to occur in a level field, thus suggesting that the Cu status of a field may not be adequately described by assessing the Cu levels of composite field samples. Key words: DTPA-extractable Cu, soil survey, critical level, spatial variability

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