Soil strength/penetration resistance of lowland puddled soil is an important parameter for designing farm machinery. This study was aimed to estimate the overall penetration resistance of lowland puddled soils through the assessment of bulk soil parameters. Penetration resistance and bulk soil parameters including moisture content, bulk density, particle density, porosity, texture and organic matter content were measured under real field condition and evaluated to identify the suitable determinants to explain the variation of soil penetration resistance and their relationships. Results revealed that measured penetration resistance by Eijkelkamp hand penetrometer and bulk soil parameters except particle density, notably varied with weed controlling methods, depth of the soil and the time. Penetration resistance showed a significant relationship with bulk density (BD), moisture content (MC) and porosity (

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Soil shear strength (SS) is an important

Lower performances of traditional threshing methods, labour shortage, reduced turn-around time and use of high yielding varieties have inevitably forced farmers to shift into mechanical grain threshing. Recently introduced four-wheel tractor driven high capacity combined paddy thresher gained popularity among Sri Lankan farmers. However, this thresher has not been properly evaluated. This study evaluated the field performances and economics of this thresher and monitored the emission of chaff and dust to compare the commercial makes, grain types and operational conditions. This study was carried out in the North Central Province of Sri Lanka, during the Maha season of 2008/2009. Air monitoring on inhaled air was done by filtration technique, using special masks and surrounding environment by gravity techniques, using Polyurethane foam. As per the RNAM test code procedures, three commercial makes of high capacity combined paddy threshers were evaluated under different operational conditions for long and short grain paddy varieties with two replicates. The combined paddy threshers showed 1.8% damaged grain, 0.2% blown grains, 1.6% grain losses, 96.7% threshing recovery, 98.8% threshing efficiency, 90.7% cleaning efficiency, 1178 kg/h corrected output capacity and Rs. 2744 actual cost of threshing per metric ton of output at 14% moisture content. Though this thresher is suited for Sri Lankan conditions, it is associated with considerable amount of chaff and dust content such as; 2.04 mg/cm 2 /h in inhaled air and 35.59 mg/cm 2 /h in surrounding environment. The performance, economics and chaff and dust emission vary with make of the machine, grain type and operational conditions. Grain moisture is the most dominantly affected factor for the thresher performance.

Weeds are the major reason for the significant yield reduction in rice cultivation worldwide. Power weeders have been introduced to rice cultivation as an alternative solution for the controversial herbicide applications. The aim of this study was to appraise the newly designed burial type lowland power cultivator through a comparative performance assessment including cost economics. Five weeding methods using Conoweeder (T 1), Modified "Asakura" wooden clog (T 2), Rotary power weeder (T 3), Newly designed lowland power cultivator (T 4) and manual weeding (T 5 as the control) were evaluated. The T 4 showed a significantly high field capacity of 0.04 ha/h, which is 8 times higher than T 5 , high field efficiency of 88.30% and weeding efficiency of 62.29% which was similar to the performance of T 5. Significantly high performance indexes were observed in T 2 and T 4 (461.65) followed by T 1 and T 3. Plant damage percentage, maximum tiller number and the yield did not show any significant variation (p>0.05) among weed control methods assessed. Further, the T 4 showed a significantly low cost of weeding of 6583 Rs/ha which was 76% of cost reduction of the T 5 , and moderately high break-even point of 0.88 ha/yr suggesting that it is appropriate for the medium and large scale farmers. Moreover, T 4 showed low fuel consumption (0.556 L/h) and power requirement (0.57 kW) representing 48% and 42% respective reductions over the T 3. Further, T 4 showed the significant lowest weed re-growth rate which is essential for sustainable weed control. Based on the above results, newly designed burial type power cultivator could be recommended for medium and large scale paddy farming, since it showed high performance compared to other methods assessed. Machine performance could be further improved by high speed, light weight design with efficient turning mechanism. Besides, it is suggested to conduct detailed ergonomic evaluation in future investigations.