Foliar N applications on wheat (Triticum aestivum L.) have increased grain protein. Foliar N timing evaluations have been minimal. The objectives were (i) determine the optimal timing of foliar N for increased grain protein of hard red winter wheat (HRWW) and spring wheat (HRSW), (ii) evaluate effect of foliar N on grain yield, and (iii) determine relationship of grain protein to foliar N application and grain yield. Foliar N was applied at Feekes stage 10.0 (boot) or 10.8 (postpollination) on two cultivars of HRWW and HRSW each year from 1995 to 2000. The foliar N rate (33.7 kg N ha−1) was applied as 1:1 solution of urea ammonium nitrate (UAN) and water. Fertilizer N for a 3360 kg ha−1 grain yield goal was broadcast as UAN after planting. Soil type was Estelline silt loam (fine‐silty over sandy or sandy‐skeletal, mixed, superactive, frigid Calcic Hapludoll). Postpollination foliar N gave the highest grain protein during all years. Grain yield was significantly reduced 5% by boot stage foliar N for HRSW. Neither timing application significantly reduced HRWW grain yield. All wheat data were pooled to relate grain yield level and protein response to foliar N. Grain protein and yield from plots without foliar N were inversely related (r2 = 0.57). Postpollination foliar N increased protein 70% of the time when yield goal was exceeded compared with only 23% when it was not. These results show that postpollination foliar N gave higher grain protein and was most effective when planned yield goal was exceeded.

The effects of nitrogen (N) management systems on Rose and Arapahoe hard red winter wheat (Triticum aestivum L. Emend. Thell.) were measured. Nitrogen fertilizer rates of 0,55,110, and 165 kg N ha -1 were surface broadcast as a full N rate application atpreplant or were split-applied as two half N rates applied in the fall and spring. Supplemental N was also applied as a foliar spray treatment after anthesis at either 0 kg N ha -1 or 33 kg N ha -1 as a diluted urea-ammonium nitrate solution. The grain yield of Arapahoe was generally higher than Rose across treatments, but protein was slightly lower. Splitting the N application lowered yield somewhat in both varieties compared to the entire N rate applied at preplant, but grain protein increased by nearly 0.8% with the split application over the preplant application. Grain protein also increased up to 1.6% with a late season foliar N application despite some leaf damage compared to no foliar N. Grain yield was correlated to many agronomic parameters measured throughout the growing season, but grain protein was correlated only to shoot N concentration in samples harvested at the soft dough stage (Feekes stage 11.2).

et al., 1990; Stark and Tindall, 1992; Wuest and Cassman, 1992;Knowles et al., 1994). Other researchers have mea-Foliar N applications on wheat (Triticum aestivum L.) have insured increases in grain protein concentration from apcreased grain protein. Foliar N timing evaluations have been minimal.plications of late-season N either as foliar sprays or dryThe objectives were (i) determine the optimal timing of foliar N for increased grain protein of hard red winter wheat (HRWW) and spring topdress fertilizers even though early-season N applicawheat (HRSW), (ii) evaluate effect of foliar N on grain yield, and tions were more than sufficient for potential grain yield (iii) determine relationship of grain protein to foliar N application (Pushman and Bingham, 1976; Westcott, 1998). and grain yield. Foliar N was applied at Feekes stage 10.0 (boot) or Research reports investigating the influence of foliar-10.8 (postpollination) on two cultivars of HRWW and HRSW each applied N on wheat grain protein concentration are not year from 1995 to 2000. The foliar N rate (33.7 kg N ha Ϫ1 ) was applied Plant Sci. Dep., South Dakota State Univ., Box 2207A, Brookings, quired nutrient recommendations for N, P, K, and Cl for a SD 57007. Received 13 Dec. 2001. *Corresponding author (anthony_ bly@sdstate.edu).Abbreviations: HRSW, hard red spring wheat; HRWW, hard red winter wheat; UAN, urea ammonium nitrate. Published in Agron.

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Tillage activities play a crucial role in impacting soil physical and chemical properties, which in turn alter soil biochemical activities and microbial community structure. In this study, responses of soil biochemical activities and microbial community structure to short-term (NT S , <5 years) and long-term (NT L , >10 years) no-till (NT) systems were studied in comparison with conventional till (CT) at four different locations (Garretson, Crooks, Beresford and Mitchell) in South Dakota, USA. Data showed that the NT L resulted in increased soil labile and microbial biomass carbon (C) and nitrogen (N) compared with the CT treatment at the Garretson, Crooks and Beresford sites. At the Crooks and Beresford sites, soils under NT L and NT S had significantly increased the β-glucosidase, urease, arylamidase, acid and alkaline phosphatase and arylsulphatase enzyme activities compared with those under CT treatment. The β-glucosidase, urease, acid phosphatase and arylsulphatase enzyme activities showed significant correlations with the microbial biomass content of the soils. Phospholipid fatty acid (PLFA) analysis showed increased PLFA content in NT L soils compared with the CT. The content of total bacterial, actinobacterial, Gram-positive bacterial, total fungal, arbuscular mycorrhizal fungal (AMF) and saprophyte PLFAs was consistently increased in the NT L and NT S compared with the CT soils at the Garretson site. These differences were more pronounced between NT L and CT systems than between NT S and CT systems in most of the studied sites. The findings suggest that usage of NT for a longer duration is highly beneficial to soil labile C and N pool retention and enzyme activities, and provides less disturbance to soil microbial activities and their functions, which in turn regulates nutrient transformation. Our results also suggest that converting CT soils into NT can improve some soil