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Persistence of 1.12, 2.24, and 3.36 kg/ha of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] applied preemergence to corn (Zea maysL. ‘Funk's 4761′) was determined in three soils, each providing a range of pH from 5 to 7. Samples of surface soil from each plot were collected at intervals after atrazine application until there was no evidence of phytotoxicity to oat (Avena sativaL. ‘Florida 501′) in bioassay. Persistence (Y50) was defined as the number of days following atrazine application until bioassay indicated 50% relative growth of oats (no atrazine = 100% growth). This period ranged from 24 to 178 days, depending upon soil type, pH, and atrazine rate. Persistence of atrazine increased with increasing soil pH. The effect of soil pH was essentially the same at each atrazine rate and did not vary appreciably with years in a given soil. In McLaurin sandy loam, atrazine persisted 8 to 9 days longer with each unit increase in soil pH. In Hartsells fine sandy loam and Decatur silt loam, atrazine persistence increased 9 to 13 days and 29 days, respectively, with each unit pH.

Distribution of As with depth in soil was determined after 4 years of repeated applications of monosodium (MSMA), monoammonium (MAMA), and disodium methanearsonate (DSMA) to turf. Arsenic concentrations decreased with depth. Percentage recovery of applied As in the upper 30 cm of soil decreased with increasing application rates. Yields of cotton (Gossypium hirsutum L.), soybeans (Glycine max L. Merr.), sorghum‐sudan hybrid (Sorghum vulgare Pers. × S. sudanense (Piper) Stapf), corn (Zea mays L.), oats (Avena sativa L.), vetch (Vicia villosa Roth), and crimson clover (Trifolium incarnatum L.) were not affected by previous As treatments. Seed of cotton and soybeans accumulated more As than corn or forage from sorghum or the winter crops. Uptake of residual As was greater from MSMA than from DSMA or MAMA, and from the high rate of application than from the medium or low rates. About 90% of the soil As content occurred in the clay fraction. Much of the soil As was extracted by NH4Cl that removed little if any P. Most of the soil P was associated with iron minerals and organic matter, while As was associated with aluminum. No appreciable organic As was found.

Toxicity of un‐ionized ammonia was the primary reason for inhibited germination and reduced growth of cotton seedlings following incorporation of plant residues in a sandy loam soil. The accumulation of ammonia in toxic amounts resulted from increased soil pH and ammonium N content, whicn were proportional to the organic N content of the residues. Plant growth decreased sharply with increasing ammonia and levels above about 10 ppm were lethal. Under sterile conditions, 1:50 plant‐water extracts did not reduce germination, but with the onset of microbial decomposition, extracts of all materials were highly toxic. At concentrations above 1 :50, alfalfa extracts reduced radicle elongation even under sterile conditions, indicating the presence of a toxic constituent, possibly saponin.