The need for an effective and nontoxic preharvest desiccant for grain sorghum (Sorghum bicolor (L.) Moench) has been recognized for many years. Studies were conducted to compare glyphosate [(N‐phosphonomethyl) glycine] to sodium chlorate and paraquat (1,1'‐dimethyl‐4,4'‐bipyridinium ion) on hybrids RS 626 and Tophand. Glyphosate was more effective than sodium chlorate or paraquat in reducing grain, leaf, and stem moisture content. Glyphosate reduced grain moisture content to 13% or lower within 1 week after treatment from original grain moisture content of 20, 30 or 40%. Glyphosate prevented growth of axillary buds of grain sorghum and killed all established johnsongrass and Coloradograss in treated agreas. Lodging of grain sorghum was insignificant for 3 weeks following glyphosate treatment, despite heavy rainfall and high wind velocity. Germination of treated grain was not affected by glyphosate at rates of 0.56 and 1.12 kg/ha. The low mammalian toxicity and the absence of phytotoxicity from soil residue suggests that glyphosate may be a valuable preharvest grain sorghum desiccant.

A laboratory procedure was developed using a cucumber (Cucumis sativus ‘Straight Eight’) root‐length bioassay to measure the relative rate of release of herbicides entrapped in various starch xanthide (SX) matrices. SX herbicide formulations placed in vials containing deionized water were decanted periodically and evaluated by bioassay to examine herbicide released into the water. In leaching experiments, fractions of effluent were collected from glass columns containing SX herbicide formulations applied to a glass‐wool pad resting on a sand bed. Collected aqueous fractions were bioassayed. The herbicides examined were salt and ester formulations of picloram (4‐amino‐3,5,6‐trichloropicolinic acid), ester formulations of 2,4‐D [(2,4‐dichlorophenoxy)acetic acid], and salt formulations of dicamba (3,6‐dichloro‐o‐anisic acid). Comparison of salt and ester starch xanthide formulations of picloram indicated that the ester formulation had a release rate three to five times slower than that of the salt formulation. Differences were noted between starch xanthide formulations of salt herbicides designated as fast and slow releases.

The preharvest application of chemical desiccants to reduce moisture content of grain sorghum (Sorghum bicolor (L.) Moench) may make it possible to eliminate costly mechanical drying of harvested grain. The objective of these experiments was to evaluate the effect of glyphosate on the viability of seed from field‐treated plants. Seed from grain sorghum plants desiccated with 1.12, 2.24 and 4.48 kg/ha glyphosate [(N‐phosphonomethyl) glycine] produced a high percentage of abnormal seedlings with varying amounts of interveinal areas completely devoid of chlorophyll. Mildly affected seedlings recovered from the symptoms and produced normal plants with normally appearing, viable seed. Severely varlegated plants died. Seed damage was greatest when treatments were applied 25 days after flowering when the grain had a moisture content of 30 to 40%. Damage decreased as time of treatment after flowering (30, 35, and 40 days) increased. The number of abnormal seedlings observed in standard germination tests corresponded to the number of variegated seedlings observed in growth evaluation studies. Similar effects were noted for genotypes ‘Top Hand’, BT− 399, and RT− 2536. The last two genotypes are similar to the female and male parents of Top Hand. Rate and time of treatment had no effect on yield of Top Hand.

Foliar application of 2.8 μg/plant of glyphosate [N-(phosphonomethyl)glycine] to greenhouse grown sorghum [Sorghum bicolor (L.) Moench ‘Tophand’] seedlings resulted in increased fresh weight. As glyphosate levels were increased to 11.2 μg/plant, diameter of the basal growth zone increased while fresh weight decreased. In growth chamber studies with sorghum and wheat [Triticum aestivum (L.) ‘Era’] seedlings, glyphosate caused the greatest reduction in fresh weight at the optimum growth temperatures for both species. Glyphosate inhibited normal production of basal buds in wheat at the optimum growth temperature and stimulated bud production at temperatures above the optimum. Under normal growth conditions, basal buds in sorghum do not develop; however, application of glyphosate stimulated basal bud development under normal and above-normal temperature conditions. Histochemical analysis of malate dehydrogenase activity in apical meristem tissue of treated sorghum seedlings indicated that growth of the apex was normal and viable.

Granule, and in some cases, tablet and ball formulations of bromacil (5-bromo-3-sec-butyl-6-methyluracil), dicamba (3,6-dichloro-o-anisic acid), picloram (4-amino-3,5,6-trichloropicolinic acid), karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxyphenyl)-1,1-dimethylurea], and tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethyl urea} were applied to three areas within 30 km of College Station in the Claypan Resource area of Texas. Woody species growing in the area included blackjack oak(Quercus marilandicaMuenchh.), post oak(Quercus stellataWangenh.), yaupon(Ilex vomitoriaAit.), winged elm(Ulmus alataMichx.), white ash(Fraxinus americanaL.), mockernut hickory(Carya tomentosaNutt.), and tree huckleberry(Vaccinium arboreumMarsh.). Granules were applied either broadcast or in rows at several intervals. Tebuthiuron was the most effective herbicide on oaks, winged elm, and white ash. Tebuthiuron and picloram were equally and most effective on yaupon, mockernut hickory, and tree huckleberry. Tebuthiuron + picloram at 2.2 + 2.2 kg/ha was the most effective herbicide treatment on huckleberry. However, a mixture of tebuthiuron + picloram (1:1 w/w) was usually no more effective than the same rate of tebuthiuron in the mixture applied alone. Tablet and ball formulations of karbutilate and tablet formulations of tebuthiuron were generally equally as effective as granules. Applications of picloram and tebuthiuron granules in rows 1.8, 3.0, 4.6, or 6.1 m apart gave control equal to broadcast applications except for picloram on yaupon. On yaupon all row spacing treatments of picloram were less effective than the broadcast treatment, whereas with tebuthiuron the 6.1-m spacing was least effective. Picloram and tebuthiuron granules applied in rows, approximately at 1.8-m intervals with a tractor, were as effective as granules applied by hand in straight rows.