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The present research was conducted so as to estimate the combing ability effects of wheat genotypes for some quantitative traits in a set of line x tester crosses developed from five parents of bread wheat (Triticum aestivum L.), of which two were considered as lines (Anmol-91 and Kiran-95) and three as testers (Imadad-05, SKD-1 and Khirman). The characters studied were tillers plant -1 , spike length, spikelets spike -1 , grains spike -1 , grain yield plant -1 and seed index. The experiment was carried out in a randomized complete block design with three replications at Southern Wheat Research Station, A.R.I. Tandojam during the rabi season, 2013-14. Results revealed that variances due to F1 hybrids, lines, testers and line x tester were significant for grain yield and almost for all other characters. Thus, showing these attributes were controlled by both additive and non-additive inheritance. Line 'Kiran-95' proved worthy general combiner for spikelets spike -1 , grain yield palnt -1 and seed index. Tester, Imdad-05 was identified as good general combiner for tillers plant -1 , spike length, spikelets spike -1 , grains spike -1 , and seed index, while tester Khirman proved promising for grain yield palnt -1 . The cross Khirman x Imdad-05 was found as potential hybrid for grain yield plant -1 , while other two crosses, namely, Anmol-91 x Khirman and Kiran-95 and Khirman also showed desirable specific combining ability for variety of characters. These parents and cross combinations may be used for varietal improvement through the simple selection in segregating generations to increase yield potential of bread wheat genotypes. This may lead in the fixation of both additive and non-additive components, while making improvement in grain yield and its attributes.

An incubation study was carried out to investigate the influence of nitrogen rates to determine optimum C/N ratio under various moisture levels for straw decomposition and sequester carbon (C) in the soil. The aim was to observe straw carbon mineralization through measuring the amount of CO 2 evolution. A clay loam topsoil mixed with maize straw was supplied with four nitrogen rates (0.04, 0.08, 0.16, 0.32 g N/kg) using (NH 4 ) 2 SO 4 to adjust C/N ratios at 82, 42, 20, and 10. Soil moisture was maintained at 55%, 70%, 85%, and 100% of field capacity incubated at 25°C for 53 days. The experiment was set up with 16 treatments arranged in complete randomized design. Results showed that mixing of straw with soil increased 50% cumulative CO 2 -C compared to controls. Averagely, about 44% of added maize straw C was mineralized to CO 2 -C. Straw addition along with nitrogen and moisture had significant relationships (P < 0.05) to cumulative CO 2 -C, soil organic C and microbial biomass C. There was a highly significant relationship (R 2 = 0.99) between CO 2 -C emission and incubation time.

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Decomposition of maize straw incorporated into soil with various nitrogen amended carbon to nitrogen (C/N) ratios under a range of moisture was studied through a laboratory incubation trial. The experiment was set up to simulate the most suitable C/N ratio for straw carbon (C) decomposition and sequestering in the soil. The purpose of this study was to determine organic C decomposition by measuring CO 2 evolution using alkali traps. Maize straw mixed with clay loam topsoil was supplied with four initial nitrogen rates (40, 80, 160, 320 mg N/0.5 g C) using (NH 4) 2 SO 4 , to adjust its C/N ratio to 80, 40, 18 and 9. The soil moisture content was maintained at four moisture levels to achieve 60, 70, 80 and 90% of field capacity. Each of the four nitrogen rates were tested against four moisture levels, arranged in complete randomized design and incubated at 20°C for 52 days. Results reveal that decomposition rates and cumulative CO 2-C was increased by about 40% in straw amended treatments as compared to the controls. On average, about 34.56% of the added straw C was mineralized to CO 2-C. Also, there was highly significant relationship between CO 2-C emission and incubation period (R 2 = 0.98). Further, straw addition with interactive effect of nitrogen and moisture had significant relationships (p < 0.05) with cumulative amounts of CO 2-C, soil organic C and microbial biomass nitrogen. In conclusion, straw returning with appropriate N doses and optimum moisture can sequester and restore organic C in soil, thereby improving soil quality.