| Popis: |
Sorghum×sudangrass hybrids increase forage yield in response to irrigation, but the effect of irrigation on the various crop growth analysis variates, such as crop growth rate (CGR), leaf area index (LAI), net assimilation rate (NAR), and specific leaf area (SLA), are unknown. The objective of this New Mexico field study was to determine the effect of irrigation amount on the growth and development of a sorghum×sudangrass hybrid crop. Treatments consisted of amount of water recieved by the crop. We labeled treatments as: wet (69.41cm total water), normal (58.85cm total water) and dry (45.60cm total water). There was a total of ten irrigations and each irrigation was applied when soil moisture tension in the normal plots reached 30 kPa. The wet, normal, and dry levels resulted in maximum plant dry weight (PDW) of 1800, 1400 and 1,000g m^; maximum leaf dry weight (LDW) of 480,440 and 410g m^; and maximum LAI of 11.4, 10.2 and 9.5 respectively. Thus, LAI and LDW did increase with increasing irrigation, but less than PDW. The increase in PDW with increasing irrigation was preferentially partitioned into grain and stalk portions rather than leaves. Leaf morphology also changed in response to irrigation. With the exception of the last part of the season, there was a general increase in the specific leaf area (SLA) with increasing irrigation. Thus, with ample moisture the canopy not only increased slightly in size (LAI) and weight (LDW), but the leaves were thicker (SLA). Changes in the LAI, LDW and SLA were small in comparison to the change in PDW. The wet, normal, and dry irrigation levels allowed maximum CGR of 324,271 and 204g week^ and maximum NAR of 49.5, 46.9 and 45.8g m^ week^. The large increases in CGR with increasing moisture were due to increases in both the LAI and NAR, but the NAR was the much larger. |
