Factors other than total seasonal rainfall may be affecting corn (Zea mays L.) and possibly grain sorghum [Sorghum bicolor (L.) Moench] yield in central Texas. It has been suggested that high temperatures in central Texas during pollination and grain filling decrease the carbohydrate reserves of corn. Soil temperature was lowered in corn and grain sorghum plots during pollination and grain formation to observe the effect of soil temperature during this critical period on grain yield. Chilled water (12 to 14 C) was circulated through copper tubing 11 cm below the soil surface in plots 6.1 m long and 4.0 m wide located on Houston Black clay soil. Soil temperature in the upper part of the root zone (7.5- to 46-cm depth) during soil cooling averaged 23 C in mulched, cooled grain sorghum plots; 22 C in mulched, cooled corn plots; and 26 C in bare, noncooled corn and grain sorghum check plots. Decreasing average soil temperature (7.5- to 46-cm depth) during pollination and grain formation from 26 to 23 C reduced grain sorghum yield, but reducing average soil temperature to 22 C had no effect on corn yield. Soil cooling caused a significant (5% level) decrease stem temperature to a height of 61 cm in corn and some stem cooling at 61 cm in grain sorghum. Stem cooling of both corn and grain sorghum decreased with distance above the soil surface. Yield data obtained indicate that soil temperature during pollination and grain filling is not a factor limiting grain yield of corn and grain sorghum in central Texas.

The differences in water-use efficiency between sorghum [Sorghum bicolor (L.) Moench] and soybean [Glycine max (L.) Merrill] were compared in terms of leaf area index (LAI), size of root system, canopy stomatal resistance (R̄c), net assimilation rate (NAR), and evapotranspiration (ET). The field water budget was measured by recording the rainfall, and irrigation water applied in relation to the ET as measured with two weighing lysimeters. The evapotranspiration rates of the two crops began to diverge about August 15. This was the period when the soybean canopy began to close and the soybean LAI increased to about 1.5 times that of sorghum. NAR for sorghum during stalk elongation and heading (Aug. 15) was nearly four times that of soybeans during that time. Divergence of the two evapotranspiration curves coincided with observed differences in canopy stomatal resistance. In August after a stress period, the R̄c for sorghum at 1 and 3 pm was nearly three times the R̄c for soybeans. The increase in R̄c for sorghum was concommitant with an air temperature increase of 3 C above the air temperature near soybeans. Sorghum had approximately twice the weight of roots per volume of soil as soybeans. Even though atmospheric demand for H₂O was similar for the two crops, sorghum was able to close its stomata more than soybeans, and thus conserve soil water even with a larger root system and more water in the soil profile resulting from reduced evapotranspiration. Water-use efficiency of sorghum (gm DM/kg H₂O) was approximately three times that of soybeans on dry matter or grain yield bases.

Common milkweed (Asclepias syriaca L.) is a deep-rooted perennial weed that has increased in occurrence in recent years and has caused much concern among landowners. Because it occurs frequently in dryland sorghum [Sorghum bicolor (L.) Moench], a 3-year competition study using paired plots was conducted to determine the degree of yield loss caused by common milkweed. Sorghum yield and number of heads per hectare were significantly reduced by common milkweed competition each of the 3 years. Common milkweed reduced average yield by 21% and number of sorghum heads per hectare by 14%. Even low populations (less than 12,000 plants/ha) of common milkweed resulted in severe yield losses. Grain weight per head was significantly reduced by common milkweed competition in 1970 and 1972 but not in 1971. Competition had no effect on sorghum 500- seed weight in 1971 or 1972. Percentage protein (Kjeldahl method) of sorghum grain was significantly increased by competition in 1972 but not in 1971.

Experiments were conducted at three locations in Kansas to see if in producing combine (3-dwarf) varieties the potential grain yield of sorghum [Sorghum bicolor (L.) Moench] had been reduced. Harvesting was done at three moisture contents, and effects on lodging, threshing loss, grain yield, and stover yield were determined. Isogenic (2-dwarf and 3-dwarf) ‘RS 650’ and ‘RS 702’ hybrid grain sorghums differing by one gene (Dw₃) were used. The tall, 2-dwarf sorghum was found to yield 12.7% more threshed grain, 11.6% more total grain, and 22.1% more stover than the short, 3-dwarf plants. The 2-dwarf sorghum lodged significantly more than the 3- dwarf in late season wind storms at three of the locations. Harvesting sorghum at about 26% grain moisture yielded 8.4% more total grain and 7.4% more stover than harvesting at 14% grain moisture. Threshing losses were significantly higher when the grain was harvested at high moisture. Threshing losses were significantly lower for the 2-dwarf than for the 3-dwarf grain sorghum.

This study was prompted by the huge feed grain deficits which increase annually in the Southeast. The need exists to find ways of increasing grain production efficiently. Cropping-tillage systems designed to accomplish this were studied. Soybeans [Glycine max (L.) Merr.] and grain sorghum [Sorghum bicolor (L.) Moench.] were double cropped following wheat (Triticum aestivum L.) on a Blackbelt soil. No-tillage and conventional tillage methods were compared for soybeans and grain sorghum; Conventional tillage was used for wheat. The 2-year average yield of soybeans was 1,708 kg/ha (25.4 bu/acre) for no-tillage and 2,250 kg/ha (33.4 acre) for conventional tillage. This difference was significant (P = .05) and was due mainly to lack of nutsedge (Cyperus sp.) control by herbicide alone in no-tillage plots. In the third year when the crop was hand-hoed, no yield differences occurred due to tillage methods. The 2-year average yield of grain sorghum was 3,249 kg/ha (48.3 bu/acre) for no-tillage and 3,868 kg/ha (57.5 bu/acre) for conventional tillage. When the crop was handhoed yield of grain sorghum was significantly higher for no-tillage (5,072 vs 4.335 kg/ha). Wheat grown after soybeans yielded significantly (P = .05) more than wheat grown after grain sorghum. This difference was attributed primarily to the bneficial effect of residual N from the previous crop of soybeans. Based on current costs and prices, the soybean-wheat double cropping system produced significantly higher net returns over specified production costs than the wheat. grain sorghum system.

Field studies were conducted to determine the influence of cotton (Gossypium hirsutum L.) and grain sorghum [Sorghum bicolor (L.) Moench.] on salt distribution in vertisol profile. Electrical conductivity of soil saturated pastes taken from the root zone (0 to 90 cm) after 4 years of sorghum ranged from 2.6 to 4.8 mmhos/cm but ranged from 4 to 7.6 mmhos/cm at 0 to 90 cm after 4 years of cotton. Chloride concentrations showed similar trends in that CI- concentrations were 9 to 12 meq/liter at 0 to 90 cm after sorghum, but were from 18 to 30 meq/liter at the same depth after cotton. The differences in salt concentrations in the soil profile after the two crops were attributed mainly to higher water infiltration rate after sorghum (5.81 cm/hr) than after cotton (1.23 cm/hr). The indicate that cropping practice can be an important factor in salt accumulation in clay soils and that the crops should be alternated to avoid excessive salt accumulation in the root zone.

Seeds from over 9,000 lines in the world sorghum [Sorghum bicolor (L.) Moench] collection were classified for endosperm phenotype to identify floury endosperm lines and evaluate each for potential increases in lysine concentration. Sixty-two floury endosperm lines were selected and analyzed for protein and lysine composition. Two floury lines of Ethiopian origin, IS 11167 and IS 11758, were exceptionally high in lysine at relatively high levels of protein. The average whole grain lysine concentration of high lysine lines IS 11167 and IS 11758 was 3.34 and 3.13 (g/lOOg protein) at 15.7 and 17.2% protein, respectively. Both lines were also high in percent oil. Carbohydrate analyses of whole grain samples of the two high lysine lines were similar to that of normal sorghum grain except for a twofold increase in sucrose concentration. The high lysine gene altered the amino acid pattern in hl hl hl endosperm tissue relative to normal endosperm checks. The major changes were increased lysine, arginine, aspartic acid, glycine, and tryptophan concentrations and decreased amounts of glutamic acid, proline, alanine, and leucine in the hl hl hl endosperm. Inheritance studies suggest that the increased lysine concentration of each line is controlled by a single recessive gene, although it is not known whether the genes from both lines are allelic. The high lysine gene(s) present in IS 11167 and IS 11758 from Ethiopia is (are) herein designated as hl. The endosperm of kernels homozygous for the hl gene is partially dented. The biological value of the high lysine lines was much higher than that of average sorghum lines. In a 28-day isonitrogenous feeding experiment the weight gain of weanling rats was three times higher on an IS 11758 ration and twice as high on an IS 11167 ration as weight gains on rations prepared from normal sorghum lines. When fed rations without any dilution except the usual 2% vitamin and 4% mineral supplementation, rats gained 94 g on high lysine sorghum (IS 11758) and 28.5 g on our current best nutritional quality sorghum line (IS 2319), versus 91.5 g on opaque-2 corn (Zea mays L.) and 30.2 g on normal corn in a 28-day feeding trial. Feed efficiency ratios for this trial were 3.0 for high lysine sorghum, 6.8 for IS 2319, 3.4 for opaque-2 corn, and 7.4 for normal corn.