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Reduced forage production, grain yield, and visual N deficiency symptoms in no-till winter wheat (Triticum aestivum L.) prompted this study. Our objectives were to determine the effect of urea placement and two nitrification inhibitors--nitrapyrin [2.chloro-6 (trichloromethyl) pyridine] (NP) and dicyandiamide (DCD)--on aerial dry matter and N accumulation. A 4-yr field study was conducted on a Renfrow silt loam soil (fine-silty, mixed, thermic Udertic Paleustoll) silt loam near El Reno, OK. The seven treatments included urea fertilizer (60 kg N [ha.sup.-1]) with and without the two inhibitors, surface broadcast or banded 3 to 4 cm below the seed row, and an unfertilized control. Aerial dry matter accumulation during autumn was higher for banded urea plus DCD (22%) and broadcast urea plus DCD (25%), than for broadcast urea without an inhibitor. Whole plant N content during autumn also was higher for banded urea plus DCD (28%) than for broadcast urea without an inhibitor. Neither inhibitor nor placement affected total dry matter accumulation measured at tillering, but differences were noted at spike emergence, grainfill, and final harvest. At spike emergence in 1991, when climatic conditions were favorable for early season wheat growth, N content was greater for broadcast urea plus nitrapyrin than for broadcast urea or banded urea without inhibitor. At final harvest, both DCD treatments exhibited greater N content than all other N treatments. In 1993, when climatic conditions were favorable for leaching, DCD was effective in slowing nitrification and increasing N uptake, regardless of fertilizer placement. Our results suggest that fall application of DCD with urea can potentially increase autumn forage production and N content, thus prolonging the grazing season or accommodating increased stocking rates., ADOPTION OF CONSERVATION TILLAGE has been slowed in many regions because of problems associated with N management. Specific examples include increased volatilization and surface runoff (Terman, 1979), greater immobilization and [...]

Research over the last two decades indicated that a class of plant bioregulators known collectively as substituted tertiary amines (STA) has the potential to increase crop productivity by increasing root growth, photosynthetic efficiency, and overall plant vigor. Although several in vitro and greenhouse studies have been conducted with these materials, few have investigated the efficacy of STA application in commercial production systems. This study was initiated to determine whether STA application on commercially grown paprika (Capsicum annuum L.) would increase yield and pigment Content. Plots were established in producer fields during the 1997 and 1998 growing seasons. Foliar spray treatments of 2-(3,4-dichlorophenoxy) triethylamine (DCPTA) as well as diethyl-2-(4-methylbenzoxy) ethylamine (MBTA) at concentrations of 0, 5, 7, 10, and 15 mg.L-1 were applied to seedlings in 1997 and foliar spray treatments of MBTA at 0. 7, and 10 mg·L-1 were applied to seedlings in 1998. Nested treatments of a plant growth enhancer (PGE) were also applied in 1998. The 7 mg·L-1 MBTA treatment resulted in a 822.2 kg·ha-1 (23.2%) yield increase in 1997 and in a 670.0 kg·ha-1 (27.7%) yield increase in 1998 over untreated controls. The 7 mg·L-1 DCPTA treatments resulted in a 565.6 kg·ha-1 (15.9%) yield increase over untreated controls in 1997. The 1998 PGE treatment resulted in an average 330 kg·ha-1 (12.8%) yield increase. Fruit pigment content was also improved significantly {p < 0.05) by certain STA treatments. STA application appears to be efficacious in commercial production paprika. [ABSTRACT FROM AUTHOR]

Commercially available plant growth regulators (PGR) and plant growth enhancers (PGE) may be used to increase crop productivity and improve fertilizer and water use efficiency. Little independent field-scale research has been conducted concerning the benefit of these materials in actual production systems. This study was initiated to determine the efficacy of foliar PGR and PGE application in the production of paprika and cayenne cultivars of pepper (Capsicum annuum L.). Three PGRs and one PGE were foliarly applied to several production pepper fields in the Pecos River valley of southeastern New Mexico during the 1997 and 1998growing seasons. The Reagan loam (fine-silty, mixed, superactive thermic Ustic Haplocalcid) soils were furrow irrigated with artesian groundwater, and individual replicated treatment blocks were a minimum 0.5 ha in size. All peppers were hand harvested. The paprika peppers were dried to constant weight, yields were determined, and paprika pigment extracts were analyzed spectrometrically. In 1997 and 1998, yield was increased by 15.1 to 24.2% in plants treated with some PGRs. PGE treatment resulted in significant paprika yield increases in 1997 and 1998 and a significant yield increase in cayenne in 1997, but did not have a significant effect on paprika pigment content. The results indicated that foliar application of PGRs and PGEs to pepper cultivars can enhance yields in commercial production fields. [ABSTRACT FROM PUBLISHER]

Abstract: Although it is widely acknowledged that rising atmospheric CO2 concentrations will increase crop root growth, no study has considered how this response could be influenced by agricultural management practices. Therefore, we examined the influence of elevated atmospheric CO2 (ambient+360μmolmol−1) on root dynamics of sorghum (Sorghum bicolor) produced under conventional (tillage following winter fallow) and conservation (no-till following clover (Trifolium repens) winter cover crop) agricultural management practices. Crops were grown in an outdoor soil bin facility and CO2 treatments were administered using open-top field chambers (OTC). Root dynamics were analyzed using minirhizotrons. In conventional tillage plots, CO2-enrichment increased sorghum seasonal root production and mortality by 58 and 59%, respectively. Root growth, however, was unaffected by [CO2] in conservation plots. Growth in CO2-enriched atmospheres increased residue production by 15 and 11% in conventional and conservation plots, respectively. Grain production was 6% greater in the conservation than conventional plots but was unaffected by atmospheric CO2. Neither carbon dioxide nor management practices had any impact on the proportion of roots that died by physiological maturity (i.e., root turnover). The fraction of roots that had died by physiological maturity decreased in a linear fashion from shallow to greater soil depths. Although management did not affect cumulative seasonal root production or mortality it did influence vertical root distribution; conservation management favored shallow root systems whereas conventional management favored deeper rooting. Data emphasize the importance of quantifying production and mortality as separate processes. This study suggests that conversion from conventional to conservation management practices might diminish stimulation of rooting by rising atmospheric CO2, at least in the C4 crop sorghum. [Copyright &y& Elsevier]