Seven fertilizer trials testing rates and combinations of N and P were conducted on corn (Zea mays L.), a grain sorghum variety [Sorghum bicolor (L) Muench.] and a sorghum hybrid in Uganda in 1964. In general, corn outyielded sorghum, and showed a better response to applied fertilizer, but the interpretation of the results was complicated by a puzzling significant negative NP interaction for sorghum. The results support the hypothesis that sorghum is better adapted to low soil fertility than is corn in Uganda, but such a conclusion cannot be established on the basis of such slender evidence as is here made available.

In 1956 a study was initiated at Manhattan, Kansas, to measure effects on crop yield and protein content of five crop rotations: continuous wheat; continuous grain sorghum, sorghum, wheat, wheat; alfalfa, (2 years), sorghum, wheat, wheat; and bromegrass (2 years), sorghum, wheat, wheat. The study had a split plot, randomized block design with four replications. Three levels of nitrogen fertilizer were superimposed over the rotation variables. Cereal crop yields were not improved by including other cereals or perennial crops in a rotation on a Geary silty clay loam, upland soil. From 1959 through 1967 average wheat yields were highest in the continuous wheat system; sorghum yields were best in the sorghum, wheat, wheat rotation, and in the continuous sorghum system. More often than not sorghum yields were reduced following the perennial crops, due no doubt to moisture deficiency. Nitrogen fertilizer, which increased wheat yields in some years and decreased them in others, had little effect on the 9-year average wheat yields. Nitrogen fertilizer generally increased sorghum yields. Protein content of cereal grain was highest in the alfalfa rotation and was increased by applying nitrogen fertilizer.

Levels of HCN-p in plants of all sorghum (Sorghum bicolor (L.) Moench) cultivars and stages decreased during ensiling. Small amounts of HCN gas were detected in the gases released during aerobic respiration, and in the gases flushed from the silo after the aerobic respiration period. The levels of HCN-p of all the forage sorghum silages approached 0 ppm; whereas, the HCN-p of the grain sorghum silage was 62 ppm.

Studies were conducted during 1968 and 1969 at Belleville, Illinois, to determine the effects of simazine (2-chloro-4,6-bis (ethylamino)-s-triazine), atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), and N level on production of grain and crude protein in wheat (Triticum aestivum (L.) and grain sorghum (Sorghum bicolor (L.) Moench). In 1968, 1.12 kg/ha simazine increased the grain yield and crude protein content in sorghum grain when the plants were under N stress. In 1969, the N stress was less pronounced and neither simazine nor atrazine increased grain yield or total crude protein in wheat or sorghum. Simazine increased the percentage crude protein in leaf samples from the sorghum plants fertilized with three N levels in 1969. The application of 112 and 224 kg/ha of N to grain sorghum in 1969 increased the grain yield by 25 and 22%, respectively, and increased the total protein content of the grain by 49 and 52%, respectively, over the control plots not fertilized with N.

Greenbug [Schizaphis graminum (Rondani)] infestations causing severe damage to a susceptible grain sorghum [Sorghum bicolor (L.) Moench], ‘Combine Kafir-60’ (CK-60), did not reduce grain yield of the resistant genotype ‘KS30.’ Losses in grain yield of susceptible CK-60 were caused by both reduced seed size and numbers of seeds per head. Grain yields of susceptible sorghum decreased as leaves were destroyed by greenbugs. As greenbug damage increased, grain protein and fiber percentages increased, while fat decreased. Greenbugs seemed to reduce yields of CK-60 more than they reduced grain quality. The data indicate that insecticides would probably not be required to prevent greenbug damage to sorghum plants possessing the resistance found in KS30 even though tolerance is a major component of its resistance.

In South Dakota, grain yields of corn grown in 102-cm rows with 35,000 plants/hectare and in 51-cm rows with 45,000 and 70,000 plants/hectare, respectively, decreased with increasing population in adverse soil-water seasons and were approximately constant during the more favorable growing seasons. Grain yields from grain sorghum planted in 102-cm rows with 175,000 plants/hectare and in 51-cm rows with 250,000 and 350,000 plants/hectare were the same in adverse years but increased markedly with increasing population during the better growing seasons. Corn, grain sorghum, and forage sorghum all gave increasing total dry-matter yields with increasing population throughout the range of populations used. Water use was nearly the same for all crops within each year, although grain sorghum grown at the lowest population tended to use slightly less water.

Emergence and yield of grain sorghum (Sorghum bicolor (L.) Moench) were studied as affected by the moisture content of seeds at sowing time. Sorghum seed sown with 8% moisture content emerged less than seed sown with either 11 or 14% moisture. Low initial seed moisture content and low substrate temperatures resulted in delayed radicle protrusion from the pericarp as well as a decrease in seed respiration rate during imbibition. Effects on emergence were great enough to be reflected in grain yields, especially under dryland conditions.

Freezing of sorghum (Sorghum bicolor (L.) Moench) leaves and stems resulted in release of hydrocyanic acid (HCN). The amount of HCN released by freezing was less than the amount released by treatment of fresh tissue with chloroform.

Experiments were conducted under irrigated, subtropical conditions to evaluate the influence of previous crop on NO₃-N distribution in the soil profile and subsequent response by cotton (Gossypium hirsutum L.) and grain sorghum (Sorghum bicolor (L.) Moench.) to plied N. Responses to N were obtained with cotton and grain sorghum if planted immediatdy after cabbage (Brassica oleracea var. capitata), but responses to N were small or non-existent if the area was fallow from September until March. Fall and winter temperatures are warm enough that N mineralization allows accumulation of NO₃-N in the soil profile and may preclude a response from application of N.