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Crop production in acid soils may be limited by several factors, including low pH. Development of acid‐tolerant cultivars requires information about differences in tolerance to low pH among crop genotypes. To determine whether differential responses to nutrient solution pH occurred among seven maize (Zea mays L.) genotypes, seedlings were grown in a growth chamber in flowing solutions at pH levels ranging from 3.3 to 6.7. Top weights, root lengths and weights, and concentrations of Ca, Mg, Fe, Zn, and Mn in plant tops were determined after 12 d. All genotypes grew well with pH of 4.0 to 5.5, with maximum dry weights of plant tops at pH 4.6 for most of the genotypes. However, all genotypes had necrotic root tips and decreased root lengths at pH 3.3, with relative root lengths (length at pH 3.3/maximum length) ranging from 0.26 to 0.55. Root weights were relatively unaffected by solution pH, but top weights decreased markedly at both pH extremes. Iron concentrations of all genotypes were decreased at pH 6.7, and interveinal chlorosis, resembling Fe deficiency, appeared in the younger leaves. Relative top weights (weight at pH 3.3/maximum weight) averaged 0.79 for Trinidad Grpl&2 and ‘PDMR Comp 1’ and 0.58 for ‘UPCA Varl’, ‘PDMR3’, Kalimpos, and Dikit at pH 3.3, and relative top weights among genotypes were positively correlated (r = 0.85) with Mn concentrations in tops. Based on relative top weight at pH 3.3, the former two genotypes were relatively more tolerant of extremely low pH than those in the latter group.

During 1975 and the spring of 1976, N requirements were determined for irrigated ‘Walter’ tomatoes (Lycopersicon esculentum Mill.) growing on Troup loamy sand with and without polyethylene mulch. Maximum soil moisture deviation occurred in the unmulched plots in the zone of illuviation to depths of 60 to 75 cm. Moisture ranged from 3 to 15% with the maximum recorded after vines were killed by frost. Highest N concentration (15.8 ppm NO3-N) occurred in mulched plots at a depth of 15 cm; whereas the highest concentration (11.5 ppm NO3-N) in unmulched plots occurred at 45 cm. The highest yield of 29.8 MT/ha was produced with 60 kg/ha N on mulched plots. The highest yield without mulch (25.6 MT/ha) required 138 kg/ha of N.

Contributions of atmospheric sulfur (S) to soil fertility at 15 locations in South Carolina were estimated during the 5‐year period 1973–77 by measuring the S content of precipitation samples accumulated at 30‐day intervals and by measuring the S collected in lead peroxide samplers exposed to the air at the same time intervals. The S content of precipitation was compared with similar data collected at three locations in 1953–55. Concurrently with the 1973–77 study, long‐term uniform field experiments designed to measure response of seven crops to S added in the fertilizer were conducted at selected locations. The mean estimated annual amount of S added to the soil in precipitation for the period 1973–75 was 11.3 kg per ha. The corresponding addition in 1953–55 was 6.3 kg/ha. The mean estimated amount of S added to the soil from the air and precipitation increased from 11.2 kg/ha in 1973 to 19.8 kg/ha in 1977. Sulfur added in the fertilizer resulted in an increased yield (10% probability level) for one crop at one location.