Indian Jou~~nal ofAgricultura1 Sciences 75 (1 0): 673-5, October 2005 Effect of residual organics: and tillage levels on wheat (Triticun? aesdvum) in a rice (Oryza sata'vra) -wheat sequence* D SARMA', J DEKA2and M C TALUKDAR3 Assatrl Agriculturul University, Joriiat 785 01 3 Received : 24 September 2003 Key words: Rice-wheat sequence, Residual organics, Tillage, Green-manure, Farmyard manure, Straw mulch, Crop establishnient Rice ( Ova sativa L.)-wheat (Triticum aesthum L. emend. Fiori & Paol.) cropping sequence is dominant in India supplying about 75 % of national food grain production. In Assam, about 17.76 lakh hectares of land is under rainy season (kharij) rice popularly known as sali rice; these areas particularly medium lands are the potential area for growing wheat after harvesting of rice. But due to limited time available between rice harvest and wheat sowing, farmers do not want to go for wheat cultivation. Because kharifrice (grown under puddle condition) leaves poor physical soil condition for the succeeding upland crop like wheat (Tripathi el al. 2003). Improvement of soil physical properties for sustained production by organic manure application is well established and suitable technology like zero tillage can ensure timely sowing of wheat in rice fields (Hobbs 2001). Therefore, the present experiment was conducted to find out suitable tillage and crop establishment techniques for wheat in winter succeeding kharifrice. A field experiment was conducted at the instructional cum research farm of the University, Jorhat (26O47'N and 94O12'E 86.6 m above mean sea-level) during 1999-2000 and 2000-2001. The soil was sandy loam in texture having organic carbon 0.68% withpH 5.6, available N, P and K; 295,11 and 56.2 kgiha respectively. The experiment was laid out in a split plot design. Wheat was grown after harvest of kharifrice. In the preceding rice crop, 3 organic manurial treatments, viz green manuring with Sesbania rostrata @ 3 tonneslha, application of farmyard manure (FYM) @ 3 tonnes/ha and control (CTL) were allocated and these treatments were placed in main plot for residual study (residual organics). In wheat crop, 6 tillage treatments, viz zero-tillage, i e opening furrows only for sowing wheat and covered by soil (ZT-SC), zero- *Short note A part of Ph D thesis submitted by the first author to the Assam Agricultural University, Jorhat, in 2001 (unpublished) 'Associate Professor (Agronomy),B N College of Agriculture, Biswanath Chariali, Assam 784 176; 'Associate Professor (Agronomy), 'Associate Professor (Soils), Department of Soil Science tillage, i e opening furrows only for sowing wheat and covered by farmyard manure (ZT-FYMC), zero- tillage, i e opening furrows only for sowing wheat and covered by soil and straw mulch (ZT-SCSM), minimum tillage and straw incorporation (MT-SI) and conventional tillage (CT) placed in the subplots. Fertilizers and plant protection measures were taken as per recommendation for the Assam. The total rainfall received during the seasons was 48.3 and 95.8 mm, respectively, for 1 999-2000 and 2000-200 1. Residual effect of green manure significantly increased gemlination count @anicles/m2) and 1 000-grain weight, grain and straw yields over farmyard manure and control in both the years (Table 1). Manurial treatments differed significantly in grain yield from each other and followed the order of GM > farmyard manure > control in both the as well as on pooled basis (Table 1). An increased grain yield of 20.8 and 10.2% due to residual effect of green manure and farmyard manure, respectively over control was recorded from pooled analysis of two years data. The higher residual effect of green manuring crop might have increased soil available nutrients, which in turn favourably affected growth and yield attributes and ultimately the grain yield. Straw yield increased to green manure over farmyard manure and control (Dwivedi and Thakur 2000). Harvest index and weed dry matter recorded a: the time of wheat harvest were not affected due to the treatments in either of the years. Conventional tillage registered highest grain yield, being statistically at par with minimum tillage-stubble remove and superior to all the zero-tillage treatment in 1999-2000 and 2000- 2001 and also on pooled basis (Table 1). Singh et al. (1998) also recorded highest grain yield of wheat due to conventional tillage over zero-tillage. Better performance of yield attributes like germination count, panicles/m2 and 1 000-grain weight in control and treatment MT-SR led to the higher grain yield. Loose and friable soils due to tillage operation possibly facilitated better root proliferation, reducing mechanical impedance over the other treatments helped in proper growth and development of the crop that was reflected in grain yield. The treatment ZT-FYMC performed better than other two