Nitrogen use and agronomic efficiency of rainfed wheat in permanent beds as affected by N fertilizer, precipitation and soil nitrate

Nitrogen (N) fertilizer is an input that has played an important role in grain yield, N use efficiency (NUE), and agronomic efficiency (AE) that needs to be studied on rainfed wheat grown in permanent beds as a planting system. The objective of this study was to test the effect of N treatments on yield, NUE and AE from 2005 to 2009. The experimental design consisted of three N rates (25, 50 and 75 kg/ha) and four N timing treatments (two single basal applications and two splits), plus a control plot (0 N). Results showed that N rate and N timing treatments had no effect on grain yield, but years, meanwhile Year–N rate interaction affected NUE and AE. Precipitation and post-harvest soil N-NO3 were identified as factors to test the years' effect on yield, NUE and AE. Regression procedures showed that the effect was greater for 25 kg N/ha treatment. The relationships between these variables and precipitation were positive, whereas the opposite occurred with soil N-NO3. NUE and AE, however, showed negative values in crop seasons with moisture constraints from precipitation (<335 mm) and soil N-NO3 (>90 kg N-NO3/ha). This result indicated that N removal and yield in these years were larger in control plots (0 N) than fertilizer application. Precipitation and soil N-NO3, rather than N treatments, explained most of the yield, NUE and AE variation over years. Therefore, to enhance that effect of weather and soil, further research on alternate N sources is needed.

Construction of dominant rice population under dry cultivation by seeding rate and nitrogen rate interaction

This study used the rice cultivar Suijing 18 to investigate the effects of morphological characteristics, photosynthetic changes, yield, as well as nitrogen absorption and utilization. The interaction between seeding rate and nitrogen rate was also assessed to identify the most suitable values of the dominant population for both factors under dry cultivation. Furthermore, the photosynthetic physiological characteristics of the upper three leaves in the dominant population were also explored. The results showed that a combination of 195 kg/ha seeding rate and 140 kg/ha nitrogen rate achieved high yield, high nitrogen utilization, and moderate morphological characteristics. This was achieved by a coordination of the combined advantages of population panicle number and spikelets per panicle. The photosynthetic potential of the population was improved by coordinating the reasonable distribution of light energy in the upper three leaves, which led to the emergence of a dominant rice population under dry cultivation.

Wheat (Triticum Aestivum L.) Response to Applied Potassium on Two Contrasting Soil Types (Vertisols and Cambisols) in The Central Highlands of Ethiopia

Background: A field experiment was conducted at Basonawerana district, Amhara regional state on two major soil types for three consecutive years to determine the effect of application of potassium fertilizer on yield and yield components of wheat and to verify the soil fertility and fertilizer recommendation Atlas of the study site. Six levels potassium were applied (0, 15, 30, 45, 60 and 75 kg K ha-1). At each potassium levels, a balanced nutrient of 92 kg N, 30 kg P, 30 kg S, 2 kg Zn, 0.5 kg Cu and 0.5 kg B ha-1 were applied. The experiment was laid out in a randomized complete block design with tree replications. Result: The analysis of variance showed that all the measured parameters were Significant influenced by year, soil type and the interaction of year x soil type. The highest grain yield, which was observed from cambisols during the first year was increased grain yield by 176.7 % (3954 kg ha-1) compared with the lowest yield observed from vertisols during the third year. Similar trend was also observed in straw yield and harvest index. On the other hand, all the measured parameters was non-significant influenced by K rate, interaction of K rate x soil type and year x K rate x soil types. Numerically, the highest yield (3878.9 kg ha-1) was observed from the highest K rate. However, the trend was not consistent. Conclusion: application of different rates of potassium fertilizer brings any significant growth and yield response on two soil types of the study sites. So, application of this fertilizer is not recommended for the crop with such high K soil status.

Genotype and Variable Nitrogen Effects on Tuber Yield and Quality for Red Fresh Market Potatoes in Minnesota

Potato (Solanum tuberosum) production generally requires added nitrogen (N), which is costly and potentially environmentally damaging. One path to limiting N application is breeding N efficient potatoes. Effective use of nitrogen, across crops, is typically characterized in terms of yield. However, tuber quality characteristics affect potato marketability, especially for red fresh market potatoes. While optimal N rates maximize yield, the genotype-specific effect of N on tuber quality traits is unclear. In order to highlight quality traits effected by N, identify germplasm with lower N requirements, and determine optimal N rates for red-skinned clones, we conducted a variable N rate experiment over two years in Minnesota. Eight red fresh market genotypes were grown in RCB factorial design with five nitrogen application rates ranging from 0 to 81.6 kg/ha. Best linear unbiased estimates were calculated for yield, skin color, skin set, and tuber shape. The models for yield and quality traits included significant genotype by N rate interaction effects, suggesting that there is variation in the way clones respond to N. Established varieties were more responsive to added N than breeding lines. Similarly, established varieties tended to produce more oblong tubers under higher N conditions, while the breeding lines remained round. Color traits also responded to N in a genotype-specific way, while the interaction effect for other traits depended on unmeasured environmental factors. No clone exhibited increased yield above the 54.4 kg/ha rate. Our results suggest that the 81.6 kg/ha rate produced less favorable phenotypes for all traits.

Incorporated Sorghum Residues Reduce Emergence and Seedling Growth of Some Crops

Allelochemicals from sorghum [Sorghum bicolor (L.) Moench] residues may inhibit the emergence and growth of other crops. We examined the effects of residues from two sorghum landraces, IS9456, a high sorgoleone producer, and IS22320, a zero sorgoleone producer. Residues were applied at 7.2 g, 14.4 g and 21.6 g kg-1 of soil. Emergence and the growth of maize (Zea mays L.), wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] were tested in three glasshouse pot experiments at the University of Zimbabwe in 2017. The 2×3 factorial experiments were laid as a randomized complete block design with six replications. Residues from IS22320 significantly (P<0.05) reduced the emergence of maize by 22.2% compared to residues from IS9456. Sorghum variety as a source of residue did not significantly (P>0.05) reduce the emergence, height, chlorophyll content or dry weight of soybean. Increasing the residue rate significantly (P<0.05) reduced the percent emergence, height, chlorophyll content and dry weight of soybean. There was a significant sorghum variety × residue application rate interaction on the percent emergence (P<0.001) and chlorophyll content (P<0.05) of wheat. Increasing the IS9456 residue application rate from 7.2 to 14.4 g kg-1 soil increased the chlorophyll content of wheat. The timing of maize and wheat planting after sorghum residue incorporation may be critical.

Safety proposals for freediving time limits should consider the metabolic-rate dependence of oxygen stores depletion

(Sadler C, Brett K, Heerboth A, Swisher AR, Mehregani N, Touriel R, Cannon DT. Safety proposals for freediving time limits should consider the metabolic-rate dependence of oxygen stores depletion. Diving and Hyperbaric Medicine. 2020 December 20;50(4):356–362. doi: 10.28920/dhm50.4.356-362. PMID: 33325016.) Introduction: There is no required training for breath-hold diving, making dissemination of safety protocols difficult. A recommended breath-hold dive time limit of 60 s was proposed for amateur divers. However, this does not consider the metabolic-rate dependence of oxygen stores depletion. We aimed to measure the effect of apnoea time and metabolic rate on arterial and tissue oxygenation. Methods: Fifty healthy participants (23 (SD 3) y, 22 women) completed four periods of apnoea for 60 s (or to tolerable limit) during rest and cycle ergometry at 20, 40, and 60 W. Apnoea was initiated after hyperventilation to achieve PETCO2 of approximately 25 mmHg. Pulse oximetry, frontal lobe oxygenation, and pulmonary gas exchange were measured throughout. We defined hypoxia as SpO2 < 88%. Results: Static and exercise (20, 40, 60 W) breath-hold break times were 57 (SD 7), 50 (11), 48 (11), and 46 (11) s (F [2.432, 119.2] = 32.0, P < 0.01). The rise in PETCO2 from initiation to breaking of apnoea was dependent on metabolic rate (time × metabolic rate interaction; F [3,147] = 38.6, P < 0.0001). The same was true for the fall in SpO2 (F [3,147] = 2.9, P = 0.03). SpO2 fell to < 88% on 14 occasions in eight participants, all of whom were asymptomatic. Conclusions: Independent of the added complexities of a fall in ambient pressure on ascent, the effect of apnoea time on hypoxia depends on the metabolic rate and is highly variable among individuals. Therefore, we contend that a universally recommended time limit for breath-hold diving or swimming is not useful to guarantee safety.

4 Effect of Inclusion Rate of Silage With or Without the Presence of Alpha-Amylase on Feedlot Performance, Carcass Characteristics, and Efficiency Measures

One hundred ninety-two Continental × British steers (initial BW 420 kg [SD 24.7]) were used in a randomized complete block design finishing study to evaluate the effects of feeding two types of silage germplasm at two inclusion rates. A 2 × 2 factorial arrangement of treatments was used with either a conventional (CON) or increased expression of alpha-amylase (Enogen, Syngenta Seeds, LLC, ENO) hybrid fed at either 12% (12SIL) or 24% (24SIL) of diet DM. Steers were blocked (n = 5) and assigned randomly within block to treatments, resulting in five pens and 48 steers per treatment. Steers were harvested after 126 (12SIL) or 140 (24SIL) days on feed. There were no silage source by inclusion rate interactions detected for live growth performance. Silage source did not affect live based average daily gain (ADG), gain to feed ratio (G:F), or final BW (FBW; P ≥ 0.35). Feeding 24% silage reduced ADG (P = 0.04) and G:F (P = 0.01) but increased FBW (P = 0.02) compared to 12SIL. A source by inclusion rate interaction was detected (P = 0.04) for calculated yield grade (YG) with steers fed 24% silage having increased YG within CON but not ENO. Hot carcass weight and ribfat were unaffected by silage source (P ≥ 0.81), but were increased by feeding 24% silage (P = 0.03 and P = 0.02, respectively). Feeding increased amounts of silage increased beef produced per hectare (P = 0.05). Conventional silage produced more beef per hectare (P &lt; 0.01) due to differences in silage yield, but source of silage did not affect feedlot performance independent of silage yield. Feeding increased amounts of silage reduced DM efficiency on a live animal basis but increased beef produced per hectare which is of major value to cattle feeders who produce the majority of their own feedstuffs.

Effect of Site Specific Nitrogen Management on Seed Nitrogen—A Driving Factor of Winter Oilseed Rape (Brassica napus L.) Yield

It has been assumed that the management of both soil and fertilizer N in winter oilseed rape (WOSR) is crucial for N accumulation in seeds (Nse) and yield. This hypothesis was evaluated based on field experiments conducted in 2008/09, 2009/10, 2010/11 seasons, each year at two sites, differing in soil fertility, including indigenous N (Ni) supply. The experimental factors consisted of two N fertilizers: N and NS, and four Nf rates: 0, 80, 120, 160 kg ha−1. Yield, as governed by site × Nf rate interaction, responded linearly to Nse at harvest. The maximum Nse (Nsemax), as evaluated by N input (Nin = Ni + Nf) to WOSR at spring regrowth, varied from 95 to 153 kg ha−1, and determined 80% of yield variability. The basic reason of site diversity in Nsemax was Ni efficiency, ranging from 46% to 70%, respectively. The second cause of Nse variability was a shortage of N supply from + 9.5 soil to −8.8 kg ha−1 to the growing seeds during the seed filling period (SFP). This N pool supports the N concentration in seeds, resulting in both seed density and a seed weight increase, finally leading to a yield increase.

Effect of inclusion rate of silage with or without alpha-amylase trait on finishing steer growth performance, carcass characteristics, and agronomic efficiency measures

One hundred ninety-two Continental × British steers [initial body weight (BW) = 420 kg (standard deviation = 24.7)] were used in a randomized complete block design finishing study to evaluate the effects of feeding two types of silage germplasm at two inclusion rates. A 2 × 2 factorial arrangement of treatments was used with either a conventional hybrid (Golden Harvest G07B39-311A, Syngenta Seeds LLC, Minnetonka, MN; CON) or a hybrid with increased expression of alpha-amylase (Syngenta Enogen Feed corn, Golden Harvest E107B3-3011A-EVT5, Syngenta Seeds, LLC; ENO) fed at either 12% (12SIL) or 24% (24SIL) of diet dry matter. Steers were blocked by source and location (source 1: first three pen replicates, n = 10 steers per pen with a fourth pen replicate of six steers per pen; source 2: one pen replicate, n = 12 steers per pen) and assigned randomly within block to treatments, resulting in five pens and 48 steers per treatment. Steers were harvested after 126 (12SIL) or 140 (24SIL) days on feed (DOF). There were no silage hybrid by inclusion rate interactions detected for live growth performance (P ≥ 0.15). Silage hybrid did not affect average daily gain (ADG), gain-to-feed ratio (G:F), or final BW (FBW; P ≥ 0.35). Feeding 24% silage reduced ADG (P = 0.04) and increased G:F (P = 0.01) but increased FBW (P = 0.02) because of greater DOF compared with 12SIL. A hybrid by inclusion rate interaction was detected (P = 0.04) for calculated yield grade (YG) with steers fed 24SIL having increased YG within CON but not ENO. Hot carcass weight and rib fat were unaffected by silage hybrid (P ≥ 0.81) but were increased by feeding 24SIL (P = 0.03 and P = 0.02, respectively). Feeding increased amounts of silage increased beef produced per hectare (P = 0.05). Source of silage did not affect feedlot growth performance of cattle but, because of slight differences in estimated silage yield, conventional silage produced more kilograms of beef per hectare (P &lt; 0.01). Feeding increased amounts of silage reduced G:F on both a live and carcass-adjusted basis but increased kilograms of beef produced per unit of land, which is paramount to cattle feeders who grow their own feedstuffs.