Dataset Information

Post-silking Factor Consequences for N Efficiency Changes Over 38 Years of Commercial Maize Hybrids.

ABSTRACT: Hybrid selection in maize (Zea mays L.) over the decades has increased post-silking dry matter (PostDM) and nitrogen (PostN) accumulation, often with an accompanying increase in one or more N use efficiency (NUE) metrics such as partial factor productivity (PFP), N conversion efficiency (NCE), and N internal efficiency (NIE). More certainty on the underlying mechanisms of how PostDM and PostN changes over time have contributed to NUE gains or losses in modern-era hybrids can only be realized by directly comparing hybrids of different eras in the context of production-system-relevant management systems. A two-year and two-location field study was conducted in Indiana with two N rates (55 and 220 kg N ha-1), three plant densities (54,000, 79,000, and 104,000 plants ha-1) and eight commercial hybrids that were released by a single seed company from 1967 to 2005. The main treatment effects of N rate, density, and hybrid dominated the PostDM and PostN responses, and there were no significant two-way or three-way interactions. Total dry matter at maturity gains averaged 80 kg ha-1 year-1 of hybrid release when averaged over locations, plant densities and N rates. Total N contents at maturity increased 0.68 kg ha-1 year-1, primarily due to annual increases in grain N content (0.8 kg ha-1 year-1). Post-silking N uptake rate increased 0.44 kg ha-1 year-1 for these era hybrids in more favorable production site-years. Slopes of grain N concentration increases per unit PostN gain were similar for all hybrids. Gains in average PFP over time were considerably higher at the low N rate (0.9 kg ha-1 year-1) than at the high N rate (0.3 kg kg-1 year-1). Hybrid gains in NIE were evident from 1967 to 1994, but not thereafter. The low N rate and higher plant densities also increased relative NIE and NCE values, but without hybrid interactions. There was no consistent trend of NIE or NCE gains in these hybrids primarily because grain and whole-plant N concentrations didn't decline over the decades at either N rate, and because NIE and NCE were often plant-density dependent.

SUBMITTER: Chen K

PROVIDER: S-EPMC5641558 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Post-silking Factor Consequences for N Efficiency Changes Over 38 Years of Commercial Maize Hybrids.

Chen Keru K Vyn Tony J TJ

Frontiers in plant science 20171011

Hybrid selection in maize (<i>Zea mays</i> L.) over the decades has increased post-silking dry matter (PostDM) and nitrogen (PostN) accumulation, often with an accompanying increase in one or more N use efficiency (NUE) metrics such as partial factor productivity (PFP), N conversion efficiency (NCE), and N internal efficiency (NIE). More certainty on the underlying mechanisms of how PostDM and PostN changes over time have contributed to NUE gains or losses in modern-era hybrids can only be reali ...[more]

PMID: 29075274

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Project description:We conducted a synthesis analysis on data from 86 published field experiments conducted from 1903 to 2014 to explore the specific consequences of post-silking N accumulation (PostN) in New Era vs. Old Era hybrids on grain yield (GY) and recovery from plant N stress at flowering (R1 stage). The Old Era encompassed studies using genotypes released before, and including, 1990 and the New Era included all studies using genotypes released from 1991 to 2014. Mean N fertilizer rates for experiments in the Old and New Era were similar (170 and 172 kg ha(-1), respectively), but plant densities averaged 5.0 plants m(-2) in the Old Era vs. 7.3 plants m(-2) in the New Era studies. Whole-plant N stress at R1 for each hybrid, environment and management combination was ranked into one of three categories relative to the N Nutrition Index (NNI). The key findings from this analysis are: (i) New Era genotypes increased the proportion of the total plant N at maturity accumulated post-silking (%PostN) as N stress levels at R1 increased-demonstrating improved adaptability to low N environments, (ii) New Era hybrids maintained similar GY on a per plant basis under both low and high N stress at R1 despite being subject to much higher population stress, (iii) PostN is more strongly correlated to GY (both eras combined) when under severe R1 N stress than under less acute N stress at R1, (iv) the New Era accumulated more total N (an increase of 30 kg N ha(-1)) and higher %PostN (an increase from 30% in Old to 36% in New Era), and (v) the change in stover dry weight from silking to physiological maturity (?Stover) has a positive, linear relationship with PostN in the Old Era but less so in the New Era. This increased understanding of how modern genotypes accumulate more N in the reproductive stage and have more PostN and GY resilience to mid-season N stress, even when grown at much higher plant densities, will assist trait selection and N management research directed to improving maize yields and N efficiencies simultaneously.

Project description:Phosphorus (P) recycling and carbon partitioning are crucial determinants of P-use efficiency and grain yield in maize (Zea mays), while a full understanding of how differences in P availability/plant P status affect these two processes underlying yield formation remains elusive. Field experiments were conducted for 3 years to investigate the maize growth, P remobilization, and carbohydrate accumulation in leaves and developing ears of plants receiving low to high P inputs. In plots that 75 kg P2O5 ha-1 and above was applied (corresponding to 7.5 mg kg-1 and higher Olsen-P concentration in 0-20 cm soil layer), no additional response occurred in leaf area, ear growth, and grain yield. Despite the higher P uptake with P fertilization above this threshold, the lack of additional plant growth and yield resulted in decreased P-use efficiency. Regardless of P application rates, P remobilization to the ear during the first half of the grain filling phase preferentially came from the stem (50-76%) rather than from leaves (30-44%), and with a greater proportion in the inorganic P (Pi) form over organic P fractions. Leaf photosynthesis was maintained under P-limiting conditions due to the greater P investment in organic P pools than Pi. More and larger starch granules were found in the bundle sheath cells at silking or 21 days after silking (DAS) than under P-sufficient conditions. The amount of total carbohydrate production and export was lower in the P-deficient plants than the high-P plants, corresponding to decreased leaf size and lifespan. Nonetheless, similar or significantly greater starch levels were observed in both cob and kernels at silking and 21 DAS, implying there was an adequate carbohydrate supply to the developing ears under the diminished kernel sink of the P starvation. In addition, there was a strong correlation between the accumulation rates of carbon and remobilized P in the developing kernels, as well as between carbon and total P. Overall, the results indicated that diminished sink size and lower capacity of carbon deposition may limit yield formation in P-deficient maize, which in turn imposes a feedback regulation on reducing carbon and P remobilization from source leaves. An integrated framework considering post-silking P recycling and carbon partitioning in maize and their effects on grain yield has been proposed.

Project description:Nitrogen (N) supply could improve the grain yield of maize, which is of great importance to provide calories and nutrients in the diets of both humans and animals. Field experiments were conducted in 2009 and 2010 to investigate dynamic zinc (Zn) accumulation and the pre-silking and post-silking Zn uptake and their contributions to grain Zn accumulation of maize with different N supply under field conditions. Results showed that only 1.2% to 39.4% of grain Zn accumulation derived from pre-silking Zn uptake, with Zn remobilization being negatively affected by increasing N supply. However, post-silking Zn uptake (0.8-2.3 mg plant-1) and its substantial contribution to grain Zn accumulation (60.6%-98.8%) were progressively enhanced with the increasing N supply. Furthermore, grain Zn concentration was positively associated with grain N concentration (r = 0.752***), post-silking N uptake (r = 0.695***), and post-silking Zn uptake (r = 738***). A significant positive relationship was also found between post-silking uptake of N and Zn (r = 0.775***). These results suggest that N nutrition is a critical factor for shoot Zn uptake and its allocation to maize grain. Dry weight, and N and Zn concentration of grain and straw were significantly enhanced with the increasing N from "no N" to "optimal N" supply (150 kg N ha-1 in 2009 and 105 kg N ha-1 in 2010), but further increasing N supply (250 kg N ha-1) generally resulted in a non-significant increase in both cropping seasons. During the grain development, N supply also generally tended to improve grain N and Zn concentrations, but decrease phosphorus (P) concentration and the molar ratio of P to Zn compared with null N application. These results suggest that grain Zn accumulation mainly originates from post-silking Zn uptake. Applying N at optimal rates ensures better shoot Zn nutrition and contributes to post-silking Zn uptake, maintaining higher grain Zn availability by decreasing the molar ratio of P to Zn, and resulting in benefits to human nutrition.

Dataset Information

Post-silking Factor Consequences for N Efficiency Changes Over 38 Years of Commercial Maize Hybrids.

Publications

Post-silking Factor Consequences for N Efficiency Changes Over 38 Years of Commercial Maize Hybrids.

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