The estimation of yield loss from defoliation and stem cut‐off is based on the assumptions that soybean (Glycine max (L.) Merr.) cultivars do not differ appreciably in their ability to recover from plant injury, recovery is similar across locations, and percentage yield loss at all reproductive stages can be approximated from research involving only three of the stages. The objective of our study was to test the validity of the assumptions by comparing the response of indeterminate and determinate soybean cultivars to 100% defoliation and 100% half‐plant cut‐off at six reproductive stages from R2 to R7. Two indeterminate cultivars, ‘Hark’ and ‘Beeson’, were studied at Ames, Iowa, and Lafayette, Ind., and two determinate cuitivars, ‘Hill’ and ‘Lee’ were evaluated at Stuttgart, Ark.The determinate cultivars had significantly greater yield reduction from 100% defoliation than did the indeterminate cultivars at all reproductive stages, except R7. Average yield reduction from defoliation for all stages was 59% for the determinate cultivars, compared with 39% for the indeterminate cultivars. Maximum yield loss from 100% defoliation occurred at R4 (86%) and R5 (88%) for determinate cultivars and at R5 (82%) for indeterminate cultivars. Average yield loss from half‐plant cut‐off was similar for indeterminate (34%) and determinate (33%) cultivars, but there was a significant interaction with stages. Yield loss for indeterminate cultivars increased from R2 to R5, then remained constant from R5 to R7. The yield loss from half‐plant cut‐off with determinate cultivars increased progressively rom R2 to R7. The determinateness of a cultivar should be considered when assessing yield reductidn from defoliation and half‐plant cut‐off during reproductive development. Damage from hail, insects, and other factors will be most accurately estimated by establishing separate loss values for indeterminate and determinate types.There was no significant difference between Iowa and Indiana in the percentage of yield loss from 100% defoliation. For the cultivars and locations studied, location effects were not important in the estimation of yield loss from plant injury.Yield loss from 100% defoliation at the six reproductive stages did not follow the relationship predicted from previous studies. Our data indicated that maximum loss for indeterminate cultivars occurred at R5, not R4 as has been assumed. Some yield loss occurred at R7 indicating that the description used to identify plants at physiological maturity was incorrect. A new description based on pod or seed maturation is needed to identify plants that have reached physiological maturity.

‘Beeson’ soybeans (Giyeine max (L.) Merr.) were treated at a vegetative (V7) and a reproductive (R3) stage of development to determine how soybeans respond to two important components of hail damage‐stand reduction and defoliation. This information is used by the crop hail industry to construct crop loss charts. Treatments consisted of 0, 25, and 50% levels of stand reduction and defoliation in all combinations at both growth stages. Defoliation was accomplished by removing designated percentage of each leaflet with a hand shears. Stand reduction alone reduced seed yield a maximum of 17% while defoliation alone reduced seed yield a maximum of 6%. The largest yield reduction (23%) occurred when the 50% stand reduction and 50% defoliation treatment was imposed during the reproductive stage. Plant height at maturity and lodging were reduced slightly by both defoliation and stand reduction treatments with stand reduction causing the most change in these parameters. More pods and heavier seed were produced on plants remaining after stands were reduced. Defoliation during the reproductive stage reduced seed yield, number of pods per plant, and lodging more than similar treatments applied at the vegetative stage. Number of seeds per pod was not significantly influenced by the treatments. From the data we concluded that low levels of defoliation removed leaf tissue which contributed little to seed production, and the soybean community was able to compensate for plants removed from the population. Most of the compensation was due to an increase in number of pods per plant.

Cassava (Manihot esculenta Crantz) is commonly intercropped with cowpea (Vigna unguiculata (L.) Walp) or peanut (Arachis hypogaea L.) in the tropics. Little is known about how intercropping these species influences efficiency of land use and yields. Cassava, cowpea, and peanut were grown as sole crops and as intercrops on a Typic Dystropept soil at Santander de Quilichao, Colombia in 1981 and1982. The objective of this study was to determine land use efficiency, yield, and yield components for cassava, cowpea, and peanut grown in intercropping and sole cropping systems. Cassava yields were reduced 2.3 to 4.7 Mg ha-• when intercropped with cowpea or peanut, except in 1982 when intercropped with cowpea. Cassava yield reductions due to intercropping were associated with the production of l.S to 3.9 fewer storage roots per plant than were produced by sole cropped cassava. When intercropped with cassava, cowpea seed yields were reduced from 3195 to 2170 kg ha-• in 1981, and from 2227 to 1328 kg ha-• in 1982. Averaged across years, peanut seed yield was reduced from 2099 to 1293 kg ha-•. Cowpea and peanut yield reductions due to intercropping were associated with the production of approximately 3.5 fewer pods per plant. Even though yields of component crops were reduced by intercropping, the cassava-cowpea and cassava-peanut intercropping systems resulted in IS to 35% greater land use efficiency for the 11-month growing season than resulted from the sole cropping systems. This is of importance in developing countries where available per capita arable land is low.Additional index words: Manihot esculenta Crantz, Vigna unguiculata (L.) Walp, Arachis hypogaea L., Land equivalent ratio.