Variation of soybean [Glycine max (L.) Merr.] growth and yield with planting date may be a response to changes in the plant, the environment, or a combination of both. Th is 2-yr experiment studied the eff ects of planting date on durations of vegetative and reproductive stages, and duration, temperature, and precipitation on yield of fi ve soybean cultivars each representing a maturity group (MG IV-VIII) under dryland conditions. Planting dates were scheduled for 14-d intervals from late April to mid-July, 2008 and 2009. Length of growing season shortened with later planting dates, and the shortening was greater for vegetative stages compared with reproductive stages, especially for later MGs. Duration of fl owering decreased with later planting date more rapidly for MG V through VIII (−0.60 to 1.18 d per planting date delay) than MG IV (insignifi cant). Pod-set duration declined with later planting date slowly for all MGs and insignifi cantly for MG IV and V in 2008. Th ere was no conclusive relationship between seed-fi ll duration and later planting date. Duration of vegetative stage was positively correlated with yield of each MG. At fl owering stage, yield of MG IV was positively correlated with temperature, while yields of MG V to VIII were positively correlated with duration, temperature, and precipitation. Precipitation during pod-set was the main factor in determining yields of all MGs. Temperature during seed-fi ll was positively correlated with yields of all MGs. Th ese results suggest that May planting dates would achieve greater yield potential for all MGs by extending duration of development stages and avoiding cooler temperature during seed-fi ll.

Delayed planting date and unfavorable environmental conditions have a negative effect on soybean [Glycine max (L.) Merr.] growth, development, and yield. Changes in photoperiod, temperature, and precipitation with delayed planting affect the duration of vegetative and reproductive stages, number of branches and pods, plant height, leaf area index (LAI), and normalized difference vegetation index (NDVI), and hence the grain yield. Delayed planting can also affect the soybean seed quality by changing the oil and protein content. Environmental factors like extremely high temperature and drought stress, which are often associated with delayed planting, have also a negative effect on plant development and yield. Compared to optimum air temperature, reduction in photosynthetic rate during heat stress decreases seed set and size, and seed yield. Drought stress during reproductive stages reduces carbon dioxide exchange rate (CER), photosynthesis, sugar production, and flow of metabolites to the expanding cells, which increases flower and pod abortion and decreases vegetative growth, duration of the seed filling stage, seed number, and seed size. Generally, the combined effect of photoperiod, temperature, and precipitation with delayed planting most likely contributes to decreased duration of vegetative and reproductive growth stages, reduced photosynthesis and plant growth, and therefore significant reduction in grain yield of soybean.

Contemporary thinking encourages diversified cropping systems as a way to sustain crop yields, protect the environment, and increase wildlife habitat. This paper reviews the benefits of diversifying the traditional peanut (Arachis hypogea L.) and cotton (Gossypium hirsutum L.) production system to include perennial grasses such as bahiagrass (Paspalum notatum Fluegge) and bermudagrass [Cynodon dactylon (L.) Pers.] and incorporating cattle (Bos taurus) into the system. Perennial grasses improve soil quality by reducing soil erosion and nitrate (NO3) leaching, increasing organic matter (OM) content, water infiltration rates, and the abundance and diversity of micro and macro flora and fauna. Cotton and peanut grown after perennial grasses are deeper rooted, have more vigorous growth, can better withstand pest pressure and environmental stresses, and often have higher yields. Including livestock in the cropping system makes more efficient use of climate and farm resources by extending the period of productive plant growth, improving economic returns, and reducing risk by diversifying the products available for sale.

Diverse cropping systems offer many advantages to farmers. We evaluated root growth, soil water infiltration, and earthworm population densities in a conventional peanut (Arachis hypogaea L.)/cotton (Gossypium hirsutum L.) rotation using conservation tillage (CT), and a peanut/cotton/bahiagrass (Paspalum notatum Fluegge) farming system. The rotations were initiated in 2000 in Quincy, FL, and in 2001 in Headland, AL, in both cases on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults). In 2003, a year with more uniform rainfall, cotton in the sod‐based rotation had larger average crown root diameter per plant (22.6 vs. 16.3 mm), root area (87.2 vs. 57.4 cm2), root length (640 vs. 460 cm), and root biomass (18.59 vs. 10.45 g) as compared with cotton in the peanut/cotton rotation. Water infiltration rates were higher in both cotton and peanut after bahiagrass compared with the conventional peanut/cotton rotation in 2003. Earthworm population densities were greater in the sod rotation compared with the traditional peanut/cotton cropping system. Water infiltration was positively correlated to earthworm population densities. Despite the improvements in soil quality, cotton yield in the sod rotation was the same as the traditional cropping systems. Cotton developed excessive vegetative growth in the bahiagrass system at the expense of lint yield. Further research is needed to determine the N rate for the sod‐based rotation in comparison with the conventional cotton/peanut rotation.