To improve management of winter wheat (Triticum aestivum L.), more information is needed on how grain yield is influenced by planting date, seeding rate, and applied P. A 3‐yr study was conducted to measure the effects of these variables on grain yield and yield components of wheat grown in low‐P soils. All soils were Crete silty clay loams (fine Montmorillonitic mesic Pachic Argiustoll) and had Bray & Kurtz no. 1 soil tests of less than 10 mg kg−1. A randomized complete block designed experiment with a split plot treatment arrangement using three planting dates (each in 1985, 1986, and 1988) as whole plots, and factorial combinations of three seeding rates and three P rates as split plots. Grain yield, spikes meter−2, kernels spike−1, and kernel weight data were collected. Relative grain yield was greatest when 400 growing degree days (GDD, 4.4 °C base temperature) accumulated between the planting date and 31 December. Increasing the seeding rate from 34 to 101 kg ha−1 resulted in yield increases of 0.39, 0.48, and 0.21 Mg ha−1 in 1986, 1987, and 1988, respectively. Increasing the P rate from 0 to 34 kg P ha−1 resulted in 0.67, 0.53, and 0.79 Mg ha−1 yield increase in 1986, 1987, and 1988, respectively. Planting date by P rate and seeding rate by P rate interactions in 1988 indicated that P reduced the negative influence of late planting and low seeding rate on grain yield. Path coefficient analysis indicated that under conditions resulting in low tiller numbers, kernel weight contributed most in yield determination, while under high tillering conditions the number of spikes meter−2 was the most important yield component. This study showed that wheat grain yields were optimized with planting dates that allowed 400 GDD accumulation before 31 December with a 101 kg ha−1 seeding rate when available soil P is sufficient.

Twin rows are being promoted as a means to increase maize yield through increased interception of photosynthetically active radiation (PAR) and plant morphology modification. The objective of this research was to explore the interactive effects of maize hybrid, plant population, and row configuration on grain yield and grain yield components, interception of PAR during vegetative growth, plant morphology, and percent lodging. Twin‐row irrigated maize produced the same grain yield as single‐row production. Small changes in plant morphology and grain yield components and 2.3 to 4.2% increased interception of PAR at the V9 (nine leaves with visible collars) stage were documented for twin rows, but the sum of these did not result in changes in grain yield. Twin‐row production increased lodging by 3.5%. Few interactions between row configuration and hybrid and target population were found, leading to the conclusion that twin‐row production of maize affords little opportunity to increase maize grain yields. Hybrid and plant population had a much larger effect on grain yield and lodging. Increasing the maize target population to 93,000 plants ha−1 maximized grain yield at 14.3 Mg ha−1, and led to small changes in plant morphology that increased lodging from 6.8 to 14.9%. Ear height had the highest direct effect on lodging in both the low (2009) and high (2010) percent lodging years. Based on these results, current promotion of twin rows is not justified for irrigated maize production in the western Maize Belt.

Remineralization of eroded enamel by dentifrices containing similar sources/concentrations of fluoride was investigated in situ. Fifty-three subjects completed a double-blind crossover study with 3 randomly assigned dentifrice treatments: placebo (0 ppm F, PD); reference (1,450 ppm NaF, RD) and test (1,450 ppm NaF + 5% KNO₃, TD). Fluoride availability for each dentifrice was analyzed in vitro by standard tests (1-min fluoride release rate and enamel fluoride uptake). The subjects wore palatal appliances holding bovine enamel specimens previously eroded in vitro. Surface microhardness was determined before and after the in vitro erosive challenge, after in situ remineralization and after a second in vitro erosive challenge. ANOVA and pairwise comparisons were performed (α = 0.05). TD was superior to RD in the fluoride release tests, but similar to RD in the enamel fluoride uptake test. The mean percent surface microhardness recovery was 21.9 (standard deviation 8.0) for PD, 28.6 (8.0) for RD and 36.0 (8.0) for TD. The mean percent relative erosion resistance change was –58.8 (12.7) for PD, –31.3 (12.7) for RD and –27.3 (12.6) for TD. Both fluoride-containing dentifrices provided superior remineralization (p < 0.001) and erosion resistance (p < 0.001) compared to PD. The percent surface microhardness recovery demonstrated by the TD was significantly greater than for the RD (p < 0.001). There was no significant difference (p = 0.073) between TD and RD in relative resistance to further erosive challenge. The results suggest that fluoride availability may be different in dentifrices with similar sources/concentrations of fluoride, providing different levels of remineralization of eroded enamel.

turity. These three developmental stages were similarly eastern Nebraska to determine how environment (location, year, water described for pearl millet by Maiti and Bidinger (1981).regime) influences number of panicles per square meter, kernel weight,For grain sorghum and pearl millet, potential kernel and kernels per panicle in determining grain yield of pearl millet and number is set during GS2 and kernel weight is deter- (Eastin et al., 1983). Yield component studies with grain Saeed et al., 1986; Rajewski et al., 1991), row number of panicles per square meter and kernels per spacing and plant population (Stickler and Wearden, panicle. Variation in kernel weight allows for a degree 1965), and soil water storage differences (Norwood, of yield compensation late in the life cycle. Increases 1992). Yield component studies with pearl millet have in kernels per panicle and in kernel weight may help shown the number of panicles per plant to be the yield compensate for low plant populations or limited tillercomponent most associated with yield changes with ing. As a result of this compensatory power, grain yield plant population, but because of profuse tillering, the in cereals is relatively insensitive to plant population number of panicles per square meter may decrease (van (Anderson, 1986); however, this compensation is less Oosterom et al., 2002) or remain nearly constant (Carthan perfect in grain sorghum (Kiniry, 1988) This research was conducted to determine the effect The treatment structure was a 4 ϫ 2 factorial at both locaof environment (year, location, water regime) on the tions. Factor one consisted of four water regimes chosen to yield components of grain sorghum and pearl millet, Great Plains production environments. The research two consisted of two crops: a pearl millet hybrid (68A ϫ 086R) focus was on western Nebraska where this experiment and an early maturing grain sorghum hybrid (DK 28E). These was conducted to determine the potential for pearl milwere the best-adapted hybrids available for the Sidney localet and grain sorghum as crops. The eastern Nebraska tion on the basis of performance tests. The experimental designs were different at the two locations becaue of a difference location provided a reference point for a region where in irrigation systems available at the two sites. At Sidney, grain sorghum is widely grown. Our hypotheses were where the irrigation system was a lateral-move system with that environment would alter those yield components drop-nozzle booms, the experiment was conducted as a ranthat are most closely associated with grain yield in pearl domized complete block design with four replications. Plot millet and grain sorghum, and that (i) under limited size was 9.1 m (12 rows 76 cm apart) wide and 9.1 m long with water stress, the number of panicles per square meter 3-m alleys between plots. At Mead, where a furrow irrigation would be the most important yield contributor for both system was used, the experiment was conducted as a randomcrops, (ii) since kernel number is ...

tices is weak (Dorsey-Redding et al., 1991;Kniep and Mason, 1989). Nitrogen effects on maize grain quality Maize (Zea mays L.) is an important crop in Brazil, and concernsin Brazil have not been documented. about grain quality are increasingly important with increasing exports and use of grain for specific end-uses. A wide range of genotypes are

The 15-item short form derived with the item impact method performed better than other short forms and appears to be sufficiently robust for use in individual patients.

Organic agriculture aims to build soil quality and provide long-term benefits to people and the environment; however, organic practices may reduce crop yields. This long-term study near Mead, NE was conducted to determine differences in soil fertility and crop yields among conventional and organic cropping systems between 1996 and 2007. The conventional system (CR) consisted of corn (Zea mays L.) or sorghum (Sorghum bicolor (L.) Moench)-soybean (Glycine max (L.) Merr.)-sorghum or corn-soybean, whereas the diversified conventional system (DIR) consisted of corn or sorghumsorghum or corn-soybean-winter wheat (wheat, Triticum aestivum L.). The animal manure-based organic system (OAM) consisted of soybean-corn or sorghum-soybean-wheat, while the forage-based organic system (OFG) consisted of alfalfa (Medicago sativa L.)-alfalfa-corn or sorghum-wheat. Averaged across sampling years, soil organic matter content (OMC), P, pH, Ca, K, Mg and Zn in the top 15 cm of soil were greatest in the OAM system. However, by 2008 OMC was not different between the two organic systems despite almost two times greater carbon inputs in the OAM system. Corn, sorghum and soybean average annual yields were greatest in either of the two conventional systems (7.65, 6.36 and 2.60 Mg ha -1 , respectively), whereas wheat yields were greatest in the OAM system (3.07 Mg ha -1 ). Relative to the mean of the conventional systems, corn yields were reduced by 13 and 33% in the OAM and OFG systems, respectively. Similarly, sorghum yields in the OAM and OFG systems were reduced by 16 and 27%, respectively. Soybean yields were 20% greater in the conventional systems compared with the OAM system. However, wheat yields were 10% greater in the OAM system compared with the conventional DIR system and 23% greater than yield in the OFG system. Alfalfa in the OFG system yielded an average of 7.41 Mg ha -1 annually. Competitive yields of organic wheat and alfalfa along with the soil fertility benefits associated with animal manure and perennial forage suggest that aspects of the two organic systems be combined to maximize the productivity and sustainability of organic cropping systems.

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