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In current study, dry-matter accumulation (DMA), pre- and post-anthesis nitrogen (N) accumulation, N translocation (NT) and dry-matter partitioning by sunflower seeds was investigated under three sowing dates (January 20, February 10 & March 2), two intra-row spacings (30 & 24 cm) and four nitrogen doses (0, 45, 60 & 75 kg ha-1) in two alluvial soils. Early sowing resulted in higher DMA and NT; leading to higher nitrogen use efficiency (NUE) that could be associated with higher pre-anthesis N accumulation. The closer intra-row spacing resulted in higher DMA by all plant parts except seed. Each graded N dose improved DMA, but improvement in dry-matter partitioning to seed was significant up to 60 and 75 kg N ha-1 during 2014 and 2015, respectively owing to higher NT under respective treatments. NUE was highest at 60 kg N ha-1 during both years. [ABSTRACT FROM AUTHOR]

Two greenhouse experiments were conducted simultaneously to evaluate polymer-coated and common urea in upland rice production. The nitrogen (N) levels used for both the N sources were from 0 to 400 mg kg−1of soil. Maximum grain yield was obtained with the addition of 167 mg N kg−1polymer-coated urea and 238 mg N kg−1common urea. Maximum value of other plant traits was obtained with N applied from 233 to 313 mg kg−1depending on plant traits and N source. Nitrogen-use efficiency (NUE) decreased with increasing N rate in the two N sources. Based on results of growth, yield, and yield components, and NUE it can be concluded that the N sources were equally effective in upland rice production. Base saturation, pH, and exchangeable calcium (Ca) increased with increasing N rates while iron (Fe), manganese (Mn), and copper (Cu) contents decreased with the increasing N rates. [ABSTRACT FROM PUBLISHER]

Pot experiments using a15N isotope technique were conducted to quantify the substitution effect of pig manure (PM) for chemical fertilizer (CF) nitrogen (N) on N-use efficiency. Treatments include a control, 100% CF N, 100% PM N, and portions of PM N (25−75%) substitution for CF N. With an increase portion of PM, N in wheat and maize plants derived from the CF (%Ndff) significantly (P< 0.05) decreased from 76.6 to 35.1% and 79.8 to 40.9%, whereas N derived from PM (%Ndfm) increased from 13.1 to 57.0% and 5.4 to 47.1%. Plant availability of PM N was equivalent to 33% and 28% of CF N for wheat and maize, and 10−17% and 12−20% of PM N were recovered by wheat and maize plants, respectively. The PM N could substitute for 33% CF N. Combinations of PM with CF did not improve N efficiency compared with equivalent rate of CF alone. [ABSTRACT FROM PUBLISHER]

Increased crop diversity and length of rotation may improve corn (Zea mays L.) yield and water- and nitrogen-use efficiency (WUE and NUE). The objectives of this study were to determine effects of crop rotation on corn yield, water use, and nitrogen (N) use. No-tillage (NT) crop rotations were started in 1997 on a Barnes clay loam (fine-loamy, mixed, superactive, frigid Calcic Hapludoll) near Brookings, S.D. Rotations were continuous corn (CC), corn–soybean [Glycine max (L.) Merr.] (CS), a 3-year rotation of corn–soybean–oat/pea (Avena sativa L. and Pisum sativum L.) hay (CSH), a 3-year rotation of corn–soybean–spring wheat (Triticum aestivum L.) (CSW), and a 5-year rotation of corn–soybean–oat/pea hay companion seeded with alfalfa (Medicago sativa L.)–alfalfa–alfalfa (CSHAA). Fertilizer N was applied to corn on all rotations at planting (16 kg N ha−1) and side-dressed (64 kg N ha−1). Average corn grain yields (1998–2007) were greatest under CSW (7.38 Mg ha−1) and least under CC (4.66 Mg ha−1). Yields were not different among CSH, CSW, and CSHAA rotations. Water-use efficiency of rotation was ordered as CSW > CSH > CSHAA > CS > CC. Nitrogen-use efficiency was greatest under CSW and least under CC. There were no differences in yield advantage (YA) among crop rotations during years with plentiful early-season rainfall (May 1–July 31). In years with low spring rainfall, YA was greatest under CSW (54%) and least under CSHAA (33%). Corn yields under extended rotations (CSH, CSW, and CSHAA) were greater than under CC and CS, but lack of rainfall may result in reduced yields under CSHAA. [ABSTRACT FROM AUTHOR]

More than 80% of broiler (chicken, Gallus gallus domesticus) litter produced annually is applied as a plant nutrient source, particularly for nitrogen (N) and phosphorus (P), to pastures. However, N losses during the process of litter N mineralization limit availability of N to crops. This study determined broiler litter N and P availability and apparent use efficiency (ANUE, APUE) to bermudagrass [Cynodon dactylon] during the first year after litter application. Treatments consisted of three litter rates (3.3, 6.6, and 13.2 Mg ha-1), a commercial N fertilizer rate that provided 358 kg N ha-1 as ammonium nitrate (NH4NO3), and an untreated control. Results showed bermudagrass dry-matter (DM) yield increased significantly with increase in litter rate. Commercial N fertilizer produced significantly greater DM yield than 3.3 and 6.6 Mg ha-1 of litter but produced less DM yield than 13.2 Mg ha-1 of litter. The overall average of ANUE from litter was 39% compared to the 59% from fertilizer. The mean litter N availabilities to bermudagrass during the first year after litter application were 48.5, 112.5, and 222 kg ha-1, corresponding to the 3.3, 6.6, and 13.2 Mg ha-1 litter rates, respectively. The overall mean of litter N mineralization, which was surface broadcast to bermudagrass plots during the first year, was 59.5% of the total litter N applied. The APUE, averaged across the rate and locations, was 13.6%, which was quite smaller than the ANUE of 39%. This finding of small APUE also validates the potential for P accumulation in soil after long-term animal manure application. [ABSTRACT FROM AUTHOR]

To determine the relationship between nitrogen (N) redistribution of oilseed rape (Brassica napus L.) varieties and N-use efficiency during later growth stages, the differences in N-use efficiency between two varieties (X-36 and X-50) were studied using the 15N labeling method with sand culture under complete nutrient solution conditions. Results showed that X-36 had greater grain yield not because of greater N uptake but because of greater grain yield per unit N in the plant and N-harvesting index. The average proportion of N in the two varieties that was redistributed from the vegetative organs to the grain was 65.1%. The redistribution amount and the proportion of N absorbed at the stem elongation stage and redistributed into the grain of two varieties were the greatest; the least were amounts absorbed at the siliquing stage. The high-N-use-efficiency variety (X-36), when compared with the low-N-use-efficiency variety (X-50), had slower redistribution speed of N before the siliquing stage, which then became faster after the siliquing stage. The amount of N redistributed to the grains and its proportion were larger, whereas those toward the silique husk were smaller. The amount of N loss from the plant and its proportion were smaller, and the velocity of N loss was also slower. This explains why varieties with high N efficiency have high N-harvesting index. At the later growth stages, N redistribution in the vegetative organs will significantly affect N-use efficiency. [ABSTRACT FROM AUTHOR]

Nitrogen (N) loss is one of the key problems faced by rice farmers, and Nitrogen-use efficiency in rice is often poor as a result of high N loss through volatilization, leaching, and denitrification. One of the ways to improve N efficiency is by using controlled-release urea (CRU). The CRU generally outperformed granular urea fertilizer in reducing N losses, stimulating plant growth, and increasing N concentrations. A field experiment with the flooded rice variety MR220 was conducted to compare the effect of six different types of CRU fertilizers on yield and N nutrition of a flooded rice cultivar. Bakau series soil (Typic Tropaquept) was used in this study. Rice plants were grown in a cylindrical culvert measuring 90 cm in diameter by 60 cm in height, and all culverts were filled with soil (approx. 210 kg). The soil was flooded and preincubated for 3 weeks to stabilize physiochemical properties before sowing. The experiment was carried out over two planting seasons on the same plot using a completely randomized design (CRD) and was replicated three times. The CRUs evaluated were CDU Uber-10, Meister-20, Meister-27, humate-coated urea, Duration type V, and sulfur-coated urea (gold-N). Fertilizer was applied once throughout the study. For both seasons, CRU-treated plants had significantly greater rice yields [6 t ha-1 (first planting harvest) and 6.2 t ha-1 (second planting harvest)] than urea-treated plants [3.7 t ha-1 (first planting harvest) and 2.2 t ha-1 (second planting harvest)], respectively. The N accumulations in rice straw and rice grains of the CRU-treated plot were significantly greater than in the control. It can be inferred that CRU performs significantly better than granular urea. This finding is important, considering the usually high N losses in rice-growing areas. [ABSTRACT FROM AUTHOR]

Efficient crop use of nitrogen (N) fertilizer is critical from economic and environmental viewpoints, especially under irrigated conditions. Nitrogen fertilizer (15N-labeled urea) and irrigation methods (drip and furrow) were evaluated on spring and fall potato cultivars under Syrian Mediterranean climatic conditions. Field experiments were conducted in the El-Ghab Valley near Hama in fall 2000 and spring 2001 on a heavy clay soil. Four N-fertilizer applications (70, 140, 210, and 280 kg N/ha) were applied in five equally split treatments for both irrigation methods. Potato was irrigated when soil moisture in the specified active root depth reached 80% of the field capacity as indicated by the neutron probe. Higher marketable tuber yield of spring potato was obtained by fertigation compared to furrow irrigation; the magnitude of tuber yield increases was 4, 2, 31, and 13%, whereas for fall potato the tuber yield increases were 13, 27, 20, and 35% for N fertilizer rates of 70, 140, 210, and 280 kg N/ha, respectively. Shoot dry matter and tuber yields at the bulking stage were not good parameters to estimate marketable tuber yield. The effect of N treatments on potato yield with furrow irrigation and fertigation was limited and not significant. Drip fertigation improved tuber yield of fall potato relative to national average yield. Nitrogen uptake increased with increasing N input under both irrigation methods. Reducing N input under both irrigation methods improved N recoveries. Increasing N input significantly increased total N content in plant tissues at the bulking stage. Spring potato yields were almost double those of fall potato under both irrigation methods and all N treatments. Nitrate (NO3) movement in the soil solution for fall potato was monitored using soil solution extractors. Furrow irrigation resulted in greater movements of NO3-N below the rooting zone than drip fertigation. Harvest index did not follow a clear trend but tended to decrease upon increasing N fertilization rates beyond 140 kg N/ha under both irrigation methods. Drip fertigation improved field water-use efficiencies at the bulking and harvest stages. Fertigation increased specific gravity of potato tubers relative to furrow irrigation. Higher N input decreased specific gravity of potato tubers under both irrigation methods. [ABSTRACT FROM AUTHOR]

Site-specific nitrogen (N) fertilizer management based on soil Nmin (soil mineral N) and the plant N status (sap nitrate analysis and chlorophyll meter (SPAD) reading test) has been shown to be effective in decreasing excessive N inputs for winter wheat in the North China Plain, but the multiple sampling of soil and plants in individual fields is too time-consuming and costly for producers and farmers. In this study, a color digital camera was used to capture wheat canopy images at a specific growth stage to assess N needs. Treatments included a farmer's N treatment (typical farmer practice), an optimum N treatment (N application based on soil-plant testing), and four treatments without N (one to four cropping seasons without any N fertilizer input). Digital images were analyzed to get red, green, and blue color-band intensities for each treatment. Normalized intensities of the red, green, and blue color bands were well correlated with soil Nmin, SPAD readings, sap nitrate concentration, and total N concentration of winter wheat. This research indicated the potential of using a digital camera as a tool combined with an improved Nmin method to make N fertilizer recommendations for larger fields. [ABSTRACT FROM AUTHOR]