fig1 shows a schematic cross - sectional view of a system 10 for feeding granular material . a central container 101 is connected to a distributing device 100 which has a take - up zone 102 and a material inlet 103 . the take - up zone 102 has an air inflow zone 102 a , which is open toward a feed channel 104 , common to at least two take - up zones , for airflow ( f ), and an outlet 102 b for material - laden airflow . from the outlet 102 b , a channel 106 runs to a row unit 107 comprising a buffer space 1071 , a feed limiting device 1072 , which is arranged to receive material from the buffer space 1071 and feed this at a predetermined rate to a coulter 1073 , with which the material is conveyed down into the earth 0 . the row unit 107 can be , for example , of such type as is shown in wo2013180619a1 . granular material is filled , for example , into the container 101 by feeding from a magazine or from sacks . replenishment of granular material can also be made during operation . an airflow f is produced in conventional manner with the aid of a fan , which can be hydraulically or electrically driven . material which is present in the container 101 falls , principally under the influence of gravity , via the material inlet 103 down to the take - up zone 102 . the airflow f is fed from the feed channel 104 via the air inflow zone 102 a to the take - up zone 102 , in which the material is taken up into the airflow f and is conveyed by this , in the form of a material - laden airflow f + m , via the outlet 102 b and the channel 106 to the row unit 107 . fig2 shows a perspective view of the distributing device 100 in fig1 , viewed obliquely from above . the airflow into the feed channel 104 is realized through an opening 104 a , while the feed channel 104 is shut off on the other side by a boundary wall 104 b . since the airflow cannot continue in the feed channel 104 , the flow f passes through the take - up region 102 and out through a number of outlets 105 . in fig2 can be seen the material inlet 103 , which is open upward toward the container 101 ( fig1 ), and twelve outlets 105 , which are associated with a respective take - up zone . fig3 shows a perspective view in cross section of the distributing device 100 in fig2 . in fig3 can be seen the material inlet 103 , the take - up zone 102 , the air feed channel 104 and the outlet 105 . fig4 a - 4 d show sectional views of an embodiment of a device for dispensing granular material , in which fig4 a shows the device viewed from the side , fig4 b shows the device viewed from above ( section b - b in fig4 a ), and fig4 c and 4 d show the device viewed from the air inflow zone of the take - up zone 102 ( section c - c in fig4 a ). in fig4 b are shown two devices arranged side by side in a common feed space 103 . the feed device in fig4 a - 4 d comprise a take - up zone 102 , which has a base 1021 , a roof 1022 and a pair of side walls 1023 . the take - up zone extends in a longitudinal direction , substantially straight between the air inflow zone 102 a and the air outlet 102 b , and thus parallel with the airflow . the take - up zone has a material inlet 102 c , which is open in a horizontal direction , transversely to the longitudinal direction . the material inlet can extend between the base and the lower portion 1023 ′ of the side wall 1023 . the roof 1022 extends along the whole of the take - up zone and is adjustable in height . the roof can have an upward facing roof surface 10221 , which , viewed in cross section transversely to the longitudinal direction , is upwardly convex , so that material which ends up on the roof surface slides off this to the side toward the feed zones 109 . preferably , the roof has a cross section with upwardly directed roof ridge , on which no material can accumulate . the roof can further have a downward facing surface 10222 , which , viewed in cross section transversely to the longitudinal direction , is flat or downwardly concave or downwardly convex . the side walls 1023 extend from the top and downward toward the base 1021 , but end at a distance from the base , so that material which is fed from the material inlet 103 to the feed zones 109 can flow from the side in toward the take - up zone 102 ( see the arrows m in fig4 c , 4 d ). a space s ( fig4 c ) is thus formed above the material , between the side walls 1023 and under the roof 1022 , through which space the airflow passes . since the roof is movable in the vertical direction , the flow area of the space s can be altered , as is shown in fig4 c and 4 d . the roof thus constitutes a controllable part . when the roof is in its upper position ( fig4 c ), the flow rate will assume its lowest value , given a certain flow and pressure from an air source . when the roof is in its lower position ( fig4 d ), the flow rate will be higher than in fig4 c , which gives the capability to entrain larger or heavier granules . the roof 1022 can be continuously adjustable , or adjustable in a plurality of steps . for example , the roof can be adjustable between an upper position , in which the flow area of the take - up zone ( the space s ) is at least equally as large as the flow area of the outlet 102 b , and a lower position , in which the flow area of the take - up zone is defined by the space s created as a result of the angle of rest which is formed as a result of the material falling from the side and in toward the center of the take - up zone 102 and the lower surface 10222 of the roof 1022 . in the lower position of the roof , its outermost edges in the lateral direction can therefore be level with lower edges of the side walls 1023 , or even somewhat lower . the base 102 can be substantially flat , viewed both in a direction parallel with the airflow f and perpendicular thereto . upstream of the air inflow zone 102 a , the base can slope in the direction toward the air inflow zone 102 a , so that material which falls down in the material inlet 103 cannot remain lying in the feed channel 104 , even if overpressure were to arise at the outlet 102 b . in fig4 b , two take - up zones 102 and three feed zones 109 are shown . the feed zones 109 are thus separated by the take - up zones 102 . the take - up zones 102 of the two devices can be openly connected to the feed zones , that is to say they can together form a common take - up region without any partition walls between the take - up zones and the feed zones . even if no partition walls are present between the take - up zones 102 , the base , which constitutes the base 106 for a number of adjacent devices , is configured in a way which means that granular material is effectively conveyed toward a respective take - up zone 102 . for example , the feed zones 109 can have an elevated portion midway between two adjacent take - up zones , wherein the bottom slopes from the elevated portion toward a respective take - up zone 102 . even though in fig4 b only two devices are shown , a system for dispensing granular material in an agricultural implement can consist of two or more such adjacent devices , depending on how many outlets to tubes or pipes are required . in order to be able to control a plurality of controllable parts , one and the same controls can be coupled to all included controllable parts , which gives a synchronized control mechanism . the controls can be configured for manual activation or connected to an actuator . a user can , for example , make desired adjustments through the use of operating devices , such as a control stick , control knob or the like , on the agricultural implement , or by operation via a control panel in a traction vehicle . in fig5 a - 5 d is shown another embodiment , which in large parts conforms to that which is shown in fig4 a - 4 d . in fig5 a - 5 d , however , no movable roof is present . instead , a bypass channel 1024 is arranged parallel with and separate from the take - up zone 102 , so that a part of the airflow f can flow past the take - up zone in the form of a bypass flow ff , without coming into contact with the material . in addition , in fig5 a - 5 d is represented the controllable part of a throttle valve 1025 , which adjustably regulates the flow ff in the bypass channel 1024 . the material inlet 102 c of the take - up zone is open in a horizontal direction , transversely to the longitudinal direction . the material inlet can extend between the base 106 and an rim 1027 of the wall 1027 of the bypass channel , which rim forms a roof for the take - up zone 102 . the bypass channel can have a bottom wall , which , viewed in cross section transversely to the longitudinal direction , is downwardly concave , so that a space s can be formed under the bottom wall 1026 , wherein the space is limited upwardly by the bottom wall and downwardly by the granular material and its angle of dip inward toward the take - up zone 102 from the lower portion 1027 of the bottom wall . given the presence of a bypass channel , roof and side walls can be integrated with one another , for example configured in one piece . the bypass channel can have a top wall , which , viewed in cross section transversely to the longitudinal direction , is upwardly convex , so that material which ends up on the top side thereof slides off this to the side toward the feed zones 109 . preferably , the top side has a cross section with upwardly directed roof ridge , on which no material can accumulate . just like the roof 1022 shown in fig4 a - 4 d , the throttle valve 1025 can be displaceable in order to be able to regulate the ratio between bypass air and air which passes through the take - up zone 102 . in order to be able to regulate a plurality of throttle valves 1025 , one and the same controls can be coupled to all included throttle valves , which gives a synchronized control mechanism . the controls can be configured for manual activation or connected to an actuator . in the central container 101 can be arranged an agitator 1011 . the agitator can be a mechanical agitator having , for example , wings or paddles which rotate to prevent the occurrence of material bridges in the container . alternatively , or by way of addition , an agitator can produce an air stream in the container . according to a further embodiment , the side walls 1023 can be displaceable in height , so that the volume of the space s can be regulated by altering the material level in the take - up zone . it is possible to make the roof 1022 and / or the side walls 1023 perform an oscillating or shaking movement , for example , up - down and / or sideways , in order to reduce the risk of formation of material bridges . it will be appreciated that the bypass channel can have an arbitrary cross section , for example semicircular , rectangular or the like , and , if the bottom side of the roof has too little curvature to form a space s , can be combined with flanges which form side walls .