Ix.'L'-iO D-jC i'IO ri
O il s and fats are important commodities in I n d i a ' s
economy. O i l seeds constitute the second largest a g r ic u l t u r a l crop in auantity as well as v a lu e . Among o i l seeds, groundnut ( Arachis hypogaea L . ) ranks f i r s t in area under cu ltiva tio n as well as in production. In 1970-71, g r o u n d n u t production of In d ia accounted for more than h a l f of the world o u t o u t ( 5 1 ).
During 1977-78 the area under groundnut was 7 . 7 2 m illio n hectares, and production was 6 . 0 6 m illio n t o n n e s ( l ) .
1 . 1 ijtate of Art of harvesting
Groundnut is grown in both northern and southern parts of the country in light to heavy s o i l s . Both bunch (erect) and spreading type of v a r ie t ie s are cu ltiva ted . The former is harvested mostly by hand uprooting, and the latter by either
sloughing or harrowing the fi e l d using animal power or tr ac to rs , and th ereafter manually c o lle c t in g the plants in small heaps* About 120 man-hours are required for h ar v e stin g one hectare of crop ( 5 8 ) .
The present mode of harvesting is disadvantageous for three reasons. F i r s t l y , dead (d iseased ) plants become detached from pods which are l e f t in the ground when the p la n ts are uprooted by hand. Secondly, in case of densely weed in fe s t e d f i e l d s , heavy loss of pods occur when harvesting is done by p u l l i n g the plants by hand ( 5 0 ) . T h ir d l y , the b e n e f i c i a l e f f e c t o f n itrogen f i x a t i o n by the crop is reduced, sin ce some of -che
JIlAPi'Kt I
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.litrogen bear in:.; nodules are also removed with plant roots fron the* so il in the harvesting process. In ad d itio n to these disadvantages, the present mode of harvesting is tedious and la bo ur intensive, h u l t i p l e cropping, which includes relay and mixed crooking, is becoming a
char act eristic feature- of modern In dian agricu lture.
'Liveliness of fi e l d operations is a basic requirement for successful multiple cropping, since a series of crops is grown in ouick succession on the same piece of la n d . In northern and southern regions, the harvest of the groundnut occurs during a period of maximum concentration of f i e l d oporations, which is obviously the period of peak labour and
energy demand. this situ a tio n , therefo re, calls for the development of appropriate groundnut harvestin, ^ equipment.
1 . 2 Design of D igging hlade
the tractor operated groundnut harvesting equipment in In d ia use single blade rather than the h alf sweeps commonly used on European and American machines, the former was preferred
in In d ian conditions as the latter resulted in greater losses in the form o f undug plants ( 5 8 ) . the drcaft requirement of the h arvesting machine equipped with the h a l f sweeps i s known to be considerably h ig h . For instance, it has been repo rted that a 20 hp groundnut combine used
15
hp for digging o p era tion alone ( 3 6 ) . F urther, the operation of harvesting equipment, h aving either sin g le blade or h a l f sweeps, in heavy s o ils r e s u lt s in the formation of bigger clods as w e ll as e x ces siv e adherence of s o i l to pods and a co n siderab le d i f f i c u l t y inCopyright
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separation o f so il from the pods, leading to su b stan tial loss in the yield of the crop.
Various investigations ( 1 1 , 13 , 22, 24, 3 2 , 4 1 , 4 8 , 55, 5 9 , 65) have shown that v ib ratin g a blade o ffe r s several advantages, such as reduced d ra ft and increased so il
p u lv e risa tio n . The latter ch aracteristic has an important bearing on improved separation,and consequently lesser damage and loss of tubers. The use of a vibratory blade allows
transfer of a fractio n of power ap p licatio n from the tractiv e phase to PTO phase-a more e ffic ie n t mode of power tran sm ission . As a consequence^ a smaller tractor weight is s u f fic ie n t for tr a c tio n ^r e su ltin g in reduced s o i l compaction. A p p lic a tio n o f vibratory blades for harvesting of root crops has reportedly been found q u ite promising ( 8 , 1 3 , 1 4 , 25, 3 1 , 5 7 , 6 2 )*
1 . 3 Scope and O b jec tiv eso f the In v estig a tio n
In view of the inherent advantages of a vibratory b la d e , its a p p lic a tio n for groundnut h arvesting may prove capable of overcoming the drawbacks o f a nonvibratory or passive blad e mentioned in Section 1 . 2 .
Although several f i e l d and laboratory in v e s tig a tio n s have been carried out for determ ining the d ra ft and power requirements o f a v ib ratory blade system, only a few of them have attempted to analyse the problem of dynamic in t e r a c t io n of v ib rato ry blade with s o i l or soil- plant medium ( 6 , 9 , 28, 4 1 , 4 7 , 5 6 , 6 5 ) .
In order to predict the performance o f a groundnut
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harvesting equipment, basic laws governing the in te ra ctio n of vibratory blade-soil-groundnut plant medium (SPM) have to be
understood. Therefore, this project aimed at a theoretical as well as experimental in v estig a tio n of the in te ra ctio n with
SPM of a blade subjected to forced lo n g itu d in a l v ib r a t io n . This intera ctio n is inherently complex due to the random
spread of the groundnut plant roots and pods in the s o i l . Obviously the strength o f the SPM v arie s with the maturity of the crop, moisture content and bulk density of s o i l , and
changes in s o i l structure brought about by roots and pods.
Therefore, the actual fie ld conditions were simulated in an indoor s o il b i n by tran splan tin g the plants excavated (along s o il monolith) from the f i e l d . A rectangular ridge of uniform cross-section with the transplanted groundnut plant- soil
monoliths simulated actual fie ld conditions for a one
dimensional cutting process. The set of s o i l bin experiments f a c il it a t e d an in v es tig a tio n of the comprehensible behaviour o f the b la d e - SPM intera ctio n under various operating
parameters, such as amplitude and frequency of v ib r a t i o n , blade l i f t a n g le , and forward v e lo c it y . Optimum operating
system parameters were determined from these s o i l b in
experiments and a prototype tractor mounted v ib rato ry groundnut d igger was d e s ig n e d , constructed and tested under a c t u a l f i e l d c o n d it io n s .
The fo llo w in g were the s p e c ific o b je ctiv es of t h is in v e s tig a tio n :
1 . To study the main dynamic parameters of s o i l and SPM.
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2* To develop a mathematical model o f dynamic blade- soil and blade-SPM interaction based on the a n aly sis of the one dimensional sin uso id al cu ttin g process.
3 . To determine the effect of operating blade system parameters, such as l i f t angle, amplitude and
frequency of v ib r a t io n , and forward v e l o c it y , on the d ra ft and power requirements under controlled
laboratory c o n d itio n s.
4 . To evaluate the effec t of blade l i f t a n g le , amplitude and frequency o f v ib r a t io n on so il breakup.
5 . To d e s ig n , develop and construct a prototype tractor mounted vibratory groundnut digger and to test it under actual fie ld conditions.
