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Perennial grasses can be grown in subtropical areas of the world having little frost damage, but, in many areas low temperatures (1 to 10 C) at higher elevations and lack of moisture may restrict growth of most subtropical forages and create critical feed shortages for livestock. A study of the seasonal distribution of forage production of subtropical grasses was conducted to determine production and quality and to develop improved management practices. Sixteen grasses (four Cynodons, three Paspalums, eight Digitarias, and one Brachiaria) were grown with and without irrigation and harvested at two stubble heights (5 and 10 cm) at 30‐day intervals for 30 consecutive months (March 1973 through August 1975). The experiment was conducted at the Immokalee Research Center in south Florida on a sandy siliceous, hyperthermic, Arenic Haplaquod (Immokalee fine sand) soil. Winter forage production (October through March) was highest for Cynodon spp (27% of total annual yield) and lowest for Paspalum spp. (14% of total annual yield). Plants cut at a 5‐cm stubble initially outyielded plants harvested at 10 cm. However, after 2.5 years little difference was observed in dry matter yield between stubble heights, except for the Paspalum spp. and Brachiaria sp. which continued to produce more forage at the 5‐cm stubble height. Little difference was observed in percentage crude protein and IVOMD between grass entries harvested during the summer growth period with the exception of Brachiaria which was significantly higher in IVOMD. Both crude protein and IVOMD were much lower in forage harvested during the summer than the winter for all grasses, again with the exception of the IVOMD for Brachiaria which had a summer‐winter range of 58 to 64%. This entry was one of the highest in dry matter yield, crude protein, and IVOMD percentage, but produced 83% of its dry matter during the summer. Irrigation had little effect on dry matter production at any season. Higher IVOMD was obtained from cut short with no irrigation. These data indicated that Cynodons harvested at a 5‐cm stubble produced highest dry matter production during the cool winter season, containing high crude protein and IVOMD levels. Dry matter yields in summer were 200 to 300% higher than in winter, however, forage quality was much lower during the summer.

In subtropical latitudes temperate crops can be grown during the cool months but the growing season is restricted by the termination and beginning of hot weather. Postponing sowing date in south Florida from October to November to January resulted in 150, 130 and 110-d growing seasons respectively. Dry matter (DM) yields of turnip, swede, rape and kale were lowered by each later sowing date and shorter growing season, and crude protein (CP) concentration was the same as for, or was increased by late sowing. In vitro organic matter digestibility (IVOMD) of turnip, swede and rape leaves was not affected by sowing date, but roots of turnip and swede from the earlier sowings and longer growing seasons were more digestible. Yield of the four species depended on harvest management as well as date of sowing and length of growing season. Total yield of turnip and swede were unaffected by harvest management but multiple cutting resulted in greater leaf yields and smaller root yields, whereas stockpiling resulted in smaller leaf yields and larger root yields. Kale produced more DM when harvested once at the end of the winter growing season but rape produced the greatest DM yield when sown in October and harvested

Heptachlor, chlordane, methoxychlor, lindane, aldrin, toxaphene, dieldrin, TDE, DDT, and BHC were applied to Arredondo fine sand at rates of 12.5, 50, and 100 ppm. of the active ingredient. The soil was placed in 2‐gallon pots and maintained in a greenhouse throughout the study. The first crop of Stringless Black Valentine beans, planted 2 weeks after treatment, showed that BHC decreased germination; all other insecticides increased germination or had no effect. Root and top weights were decreased by chlordane, lindane, aldrin, dieldrin, TDE, DDT and BHC. Only top weights were reduced by methoxychlor. Heptachlor and toxaphene had no effect on growth. Germination and root growth of a second crop of beans, seeded 11 months after application of the insecticides, were not affected; top growth was significantly reduced by lindane, aldrin, TDE, DDT, and BHC. Microbial data, obtained 1 month after application of the insecticides, indicated that they had no effect on the numbers of bacteria in the soil. Dieldrin increased the numbers of fungi; all others had no effect. Carbon dioxide evolution was increased by toxaphene, dieldrin, TDE, DDT, and BHC; the others had no effect. Nitrate production was decreased by heptachlor, lindane, and BHC; increased by toxaphene, TDE, and DDT; and unchanged by the others. Sixteen months after application of the insecticides no significant changes occurred in numbers of fungi and bacteria or carbon dioxide evolution. Nitrate production was reduced by DDT and BHC. Based upon the measurements made in this study, the growth of Stringless Black Valentine beans was influenced more than the microorganisms by the presence of insecticides in the soil. Until more specific information on microbial responses to these materials has been obtained, it appears that toxicity of higher plants will be the earliest warning of phytotoxic amounts of chlorinated hydrocarbon insecticides in the soil.