Ritu Dogra

Selenium accumulation by forage and grain crops and volatilization from seleniferous soils amended with different organic materials

Greenhouse and field experiments were conducted to study the direct and residual effect of applying different organic materials on Se accumulation by crops and volatilization from seleniferous soils of northwestern India. Among organic manures, press mud and poultry manures proved 4-5 times more effective in reducing Se accumulation by different crops than farmyard manure. Efficiency of organic manures increased with increase in application rates. Application of both press mud and poultry manures reduced Se accumulation by 44-97% in wheat (Triticum aestivum) and rapeseed (Brassica napus) shoots in the greenhouse; 85-92% in wheat straw, 45-74% in wheat grains, 45-74% in rapeseed straw and 76-92% in rapeseed grains under field conditions. Both the manures remained highly effective in reducing Se accumulation by the crops following wheat and rapeseed and the extent of reduction varied from 50% to 87% in maize (Zea mays) and cowpeas (Vigna sinensis) in the greenhouse and 40-89% in maize and rice (Oryza sativa) crops under field situation. Rate of Se volatilization by wheat and rapeseed crops increased by 1.8-4.0 times; the greatest increase was observed with press mud followed by poultry manure, arhar (Cajanus cajan) leaves and farmyard manure. After 134d of incubation of 500g soil amended with 2% of plant tissues, the maximum amount of Se was volatilized with cowpea leaves (385ng) followed by wheat grains, leaves of maize, sugarcane (Saccharum officcinarum), arhar, poplar (Populus deltoides) and the control (91ng). The results of this study convincingly prove the usefulness of applying press mud and poultry manure in enhancing volatilization and retarding the transfer of Se from soil to plant in seleniferous soils.

Effect of Radius of Curvature and Spading Frequency of Spading Machine on Physical Properties of Soil

The effect of radius of curvature and spading frequency on various dependent variables, i.e. weighted mean clod size, soil bulk density, cone index and cone index ratio were studied. The experiments were conducted in soil having 15.7 per cent clay, 53.6 per cent silt, and 30.7 per cent sand. During experimentation, moisture content of soil was maintained between 13 and 14 per cent. The radius of curvature used were C1 (Flat), C2 (15 cm) and C3 (30 cm). Four levels of bite lengths viz., 4, 6, 8 and 10 cm at travel speed of 18.47 cm/sec were selected for the study. These corresponded to four levels of spading frequencies namely F1 (1.85 cycles/s), F2 (2.31 cycles/s), F3 (3.08 cycles/s) and F4 (4.62 cycles/s). The spading frequency was determined by dividing the travel speed by the bite length. The dependent variables decreased with increase in radius of curvature and spading frequency. Weighted mean clod size, soil bulk density and soil cone index decreased with increase in spading frequency and radius of curvature. However, it increased with increase with blade width.

Performance of modified spike tooth thresher for pigeonpea (Cajanus cajan).

Grains of legumes are affected considerably due to mechanical handling. Traditional threshing practices and operations are laborious and expensive. Timeliness is another important factor. Among legumes, pigeonpea (Cajanus cajan) has considerable potential for adoption by farmers provided some of the major operations such as threshing are mechanized. The present study was aimed at optimizing important operational parameters of a modified spike tooth type thresher and crop parameters influencing threshing of pigeonpea. The thresher consisted of a 562 mm long threshing cylinder of 362 mm diameter, two aspirators, a sieve and screen. Effect of four levels of cylinder peripheral speed (16.4, 18.2, 20.1 and 21.9 m/s) and three levels of crop feed rate (700, 850 and 1000 kg/h) was studied on grain breakage, cleaning and threshing efficiency. Cylinder speed of 18.2 m/s and feed rate of 1000 kg/h resulted in optimum threshing efficiency, cleaning efficiency, breakage and non-collectable losses of 99.56 per cent, 98.63 per cent, 0.68 per cent and 0.27 per cent, respectively.