were attributed mostly to lower kernel weight and only slightly to lower kernel number (Sofield et al., 1977; High temperature is a major determinant of wheat (Triticum aesti- Chowdhury and Wardlaw, 1978; Wardlaw et al., 1989a,b; vum L.) development and growth, decreasing yields by 3 to 5% per Tashiro and Wardlaw, 1990a,b). The responses of these 1؇C increase above 15؇C in plants under controlled conditions. Even yield components to temperature varied with timing and greater yield differences have been reported between favorable and unfavorable temperature conditions in the field. The objective of this duration of treatments and among cultivars. Temperastudy was to identify the yield components of the hard red winter tures as high as 30/25ЊC decreased kernel number up wheat cultivar Karl 92 that are affected by controlled high temperature to 22% and kernel weight by as much as 38% (Wardlaw during maturation of intact plants under simulated field populations. et al., 1989a), and a greater increase in temperature from Plants at a final density of 144 m 2 were grown in the greenhouse 20/16 to 36/31ЊC from 7 d after anthesis until ripeness until anthesis and transferred to growth chambers for temperature decreased kernel weight up to 85% (Tashiro and Wardtreatment. Day/night temperatures of 20/20, 25/20, 30/20, and 35/20؇C law, 1989). were imposed from 10 and 15 d after anthesis until ripeness in two High temperatures during kernel filling (10 d after experiments, and temperatures of 25/20, 30/20, and 35/20؇C were apanthesis until ripeness) decreased wheat yield by reducplied from 20 d after anthesis until ripeness in a third experiment.ing kernel weight (Warrington et al., 1977; Tashiro and Grain yield was reduced by 78%, kernel number was reduced by 63%,

High diurnal temperatures often affect development of soybean [Glycine max (L.) Merr.], but little is known about the relative influence of high day and night temperatures on the chemical composition of the seed. This study was conducted to determine the effects of combinations of high day and night temperatures during flowering and pod set (R1-R5), seed fill and maturation (R5-R8), and continuously during the reproductive period (R1-R8) on soybean seed oil, protein, and fatty acid composition. Day/night temperatures of 30/20, 30/30, 35/20, and 35/30~ were imposed on the soybean cultivar Gnome 85 in growth chambers. The day/night temperature combinations during R1-R5 had little effect on the oil and protein concentration and the fatty acid composition of seed produced. As mean daily temperature increased from 25 (30/20) to 33 (35/30)~ during R5-R8 and 25 (30/20) to 33 (35/30)~ during R1-R8, and oil concentration decreased and protein concentration increased. Increased day temperature during R5-R8 and R1-R8, averaged across the two night temperatures, increased oleic acid and decreased linoleic and linolenic acids. When night temperature was increased at 30~ day temperature during R5-R8 and R1-R8, oleic acid decreased and linoleic acid increased. When night temperature was increased at 35~ day temperature during R1-R8, oleic acid increased, and linoleic and linolenic acids decreased. These results indicate the importance of high day and night temperatures during seed fill and maturation in the oil, protein, and fatty acid composition of soybean seed. JAOCS 73, 733-737 (1996).

We conducted a 9-ha field experiment near Boone, IA, to test the hypothesis that yield, weed suppression, and profit characteristics of low-external-input (LEI) cropping systems can match or exceed those of conventional systems. Over a 4-yr period, we compared a conventionally managed 2-yr rotation system {corn (Zea mays L.)/soybean [Glycine max (L.) Merr.]} with two LEI systems: a 3-yr corn/soybean/small grain + red clover (Trifolium pratense L.) rotation, and a 4-yr corn/soybean/small grain + alfalfa (Medicago sativa L.)/alfalfa rotation. Synthetic N fertilizer use was 59 and 74% lower in the 3-and 4-yr systems, respectively, than in the 2-yr system; similarly, herbicide use was reduced 76 and 82% in the 3-and 4-yr systems. Corn and soybean yields were as high or higher in the LEI systems as in the conventional system, and weed biomass in corn and soybean was low (≤4.2 g m −2 ) in all systems. Experimentally supplemented giant foxtail (Setaria faberi Herrm.) seed densities in the surface 20 cm of soil declined in all systems; supplemented velvetleaf (Abutilon theophrasti Medik.) seed densities declined in the 2-and 4-yr systems and remained unchanged in the 3-yr system. Without subsidy payments, net returns were highest for the 4-yr system ($540 ha −1 yr −1 ), lowest for the 3-yr system ($475 ha −1 yr −1 ), and intermediate for the 2-yr system ($504 ha −1 yr −1 ). With subsidies, differences among systems in net returns were smaller, as subsidies favored the 2-yr system, but rank order of the systems was maintained. Disciplines Agronomy and Crop Sciences | Statistics and Probability CommentsThis is an article from Agronomy Journal 100 (2008): 600, doi:10.2134/agronj2007.0222. Posted with permission. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. O ne of the key questions facing agriculturalists in the 21st century is how to produce adequate amounts of food, feed, and farm income while protecting and improving environmental quality (Robertson and Swinton, 2005). Th e need to answer this question is particularly acute in the midwestern United States, one of the largest regions of intensive, rain-fed agriculture in the world. Crop production in this region currently relies heavily on synthetic N fertilizer and herbicides to manage soil fertility and weeds (National Agricultural Statistics Service, 2003, 2007a. Concomitantly, N and herbicides emitted from midwestern cropland are detected regularly in ground and surface waters, and are viewed by many analysts as important environmental contaminants that require improved management approaches (Goolsby et al., 1999;Dinnes et al., 2002;Gilliom et al., 2006). Th e midwestern United States has also been a major recipient of agricultural subsidy payments from the federal government (Environmental Working Group, 2007), and there are persistent questions concerning farm economic viability if these subsidies were removed due to global tra...

. Total dry matter production by triticale/corn and triticale/sorghumsudangrass was 25% greater than sole-crop corn, which in turn produced 21% more dry matter than triticale/sunn hemp. Potential ethanol yield was greatest for triticale/corn, which was estimated to have the capacity to produce 1080 L ha -1 more ethanol than sole-crop corn. Crop N uptake was greater in double-crop systems during April-June, greater in the sole-crop corn system during July-August, and greater again in double-crop systems during September-October. Relative to sole-crop corn, potentially leachable soil N was reduced in double-crop systems by 34 and 25%, respectively, in the spring (mid-April) and fall (late October). High nutrient density of biomass coupled with high productivity for triticale/corn and triticale/sorghum systems also resulted in the removal of 83, 41, and 177% more N, P, and K, respectively, compared with sole-crop corn. Sustained removal of large quantities of nutrient-dense biomass from double-cropping systems would necessitate increased fertilization or integration with nutrient recycling mechanisms.