Fertilizer Response Research Articles

Innovative modeling on the effects of low-temperature stress on rice yields.

The increasing frequency and intensity of low-temperature events in temperate and cold rice production regions threaten rice yields under climate change. While process-based crop models can project climate impacts on rice yield, their accuracy under low-temperature conditions has not been well-evaluated. Our six-year chamber experiments revealed that low temperatures reduce spikelet fertility from panicle initiation to flowering, grain number per spike during panicle development, and grain weight during grain filling. We examined the algorithms of spikelet fertility response to temperature used in crop models. Results showed that simulation performance is poor for crop yields if the same function was used at different growth stages outside the booting stage. Indeed, we replaced a parameter spikelet fertility algorithm of the ORYZA model and developed the function of estimating grain number per spike and grain weight. After that, the improved equation algorithm was applied to 10 rice growth models. New functions considered the harmful effects of low temperatures on rice yield at different stages. In addition, the threshold temperatures of the cold tolerance were set for different rice varieties. The improved algorithm enhances the model's ability to simulate rice yields under climate change, providing a more reliable tool for adapting rice production to future climatic challenges.

Agronomic and socio-economic drivers of fertilizer use and crop productivity in smallholder wheat production systems in Ethiopia

Wheat (Triticum aestivum L.) is crucial for global food security and a staple crop in Ethiopia, yet farmer yields remain low, averaging 2.7 t ha⁻1 compared to over 5 t ha⁻1 at research stations. This study investigates the impact of socio-economic factors, local agronomic practices, and site-specific fertilizer management on wheat production in Goba, Lemu, Siyadebr, and Basona districts of Ethiopia. A survey of 228 households analyzed the influence of these factors on wheat productivity and fertilizer use, employing descriptive statistics, t-tests, and regression models. Results indicated that crop residue retention, improved wheat varieties, and organic fertilizers significantly increased yields, while row fertilizer application at planting had a negative effect. Fertilizer application rates varied significantly among farmers and were influenced by practices like top-dressing, monocropping, and participation in agricultural training. District-level differences in yield and fertilizer response highlighted the need for site-specific management. Multiple regression analysis revealed that key predictors of fertilizer use included cultivated land area, household income, education, small ruminant ownership, and extension contact, with larger land ownership, higher income, organic fertilizer use, and extension access being the most significant. Average yield increases due to site-specific fertilizer applications varied across districts. Overall, significant yield gains were achieved through site-specific fertilizer application across the four districts, with an average yield of 5.3 Mg ha⁻1, compared to approximately 4 Mg ha⁻1 using the local farmers' fertilizer application rates. This study underscores the importance of considering local agroecological conditions in fertilizer management to boost wheat productivity and support food security and economic development in Ethiopia.

Insights into the Response of Elemental Sulfur Fertilization on Crop Yield and Nutritional Quality of Durum Wheat

Insights into the Response of Elemental Sulfur Fertilization on Crop Yield and Nutritional Quality of Durum Wheat

The ‘photosynthetic C1 pathway’ links carbon assimilation and growth in California poplar

Although primarily studied in relation to photorespiration, serine metabolism in chloroplasts may play a key role in plant CO2 fertilization responses by linking CO2 assimilation with growth. Here, we show that the phosphorylated serine pathway is part of a ‘photosynthetic C1 pathway’ and demonstrate its high activity in foliage of a C3 tree where it rapidly integrates photosynthesis and C1 metabolism contributing to new biomass via methyl transfer reactions, imparting a large natural 13C-depleted signature. Using 13CO2-labelling, we show that leaf serine, the S-methyl group of leaf methionine, pectin methyl esters, and the associated methanol released during cell wall expansion during growth, are directly produced from photosynthetically-linked C1 metabolism, within minutes of light exposure. We speculate that the photosynthetic C1 pathway is highly conserved across the photosynthetic tree of life, is responsible for synthesis of the greenhouse gas methane, and may have evolved with oxygenic photosynthesis by providing a mechanism of directly linking carbon and ammonia assimilation with growth. Although the rise in atmospheric CO2 inhibits major metabolic pathways like photorespiration, our results suggest that the photosynthetic C1 pathway may accelerate and represents a missing link between enhanced photosynthesis and plant growth rates during CO2 fertilization under a changing climate.

Soil P-stimulating bacterial communities: response and effect assessment of long-term fertilizer and rhizobium inoculant application

BackgroundPhosphorus (P) plays a vital role in plant growth. The pqqC and phoD genes serve as molecular markers for inorganic and organic P breakdown, respectively. However, the understanding of how P-mobilizing bacteria in soil respond to long-term fertilization and rhizobium application is limited. Herein, soil that had been treated with fertilizer and rhizobium for 10 years was collected to investigate the characteristics of P-mobilizing bacterial communities. Five treatments were included: no fertilization (CK), phosphorus fertilizer (P), urea + potassium fertilizer (NK), NPK, and PK + Bradyrhizobium japonicum 5821 (PK + R).ResultsThe soybean nodule dry weight was highest in the P treatment (1.93 g), while the soybean yield peaked in the PK + R treatment (3025.33 kg ha− 1). The abundance of the pqqC gene increased in the rhizosphere soil at the flowering-podding stage and in the bulk soil at the maturity stage under the P treatment, while its abundance increased in the bulk soil at the flowering-podding stage and in the rhizosphere soil at the maturity stage under the PK + R treatment. The abundance of the phoD gene was enhanced in the bulk soil at the flowering-podding stage under the PK + R treatment. The Shannon and Ace indexes of pqqC- and phoD-harboring bacteria were higher in the rhizosphere soil at maturity under the PK + R treatment compared to other treatments. Furthermore, a comprehensive analysis of the neutral community model and co-occurrence pattern demonstrated that the application of P fertilizer alone led to an increase in the distribution and dynamic movement of pqqC-harboring bacteria, but resulted in a decrease in complexity of network structure. On the other hand, rhizobium inoculation enhanced the distribution and dynamic movement of phoD-harboring bacteria, as well as the stability and complexity of the network structure. Pseudomonas and Nitrobacter, as well as Steptomyces, Stella, and Nonomuraea, may be crucial genera regulating the composition and function of pqqC- and phoD-harboring communities, respectively.ConclusionsThese findings affirm the crucial role of fertilization and rhizobium inoculation in regulating pqqC- and phoD-harboring bacterial communities, and highlight the significance of long-term phosphate-only fertilization and rhizobium inoculation in enhancing dissolved inorganic phosphorus and mineralized organophosphorus, respectively.

<b>Performance of Candidate Varieties of Basmati Rice in Uniform Yield Trials</b>

The primary focus of rice breeding research is now on developing high-yielding rice varieties with early maturing and physio-chemical features, such as improved cooking quality, aroma, and extra-long grain. This shift in focus is driven by the growing global demand for high-quality rice. Using traditional breeding methods to trait pyramid these extremely important traits while maintaining yield and quality is a challenging task. Good grain quality(aromatic), fertilizer responsiveness, and high-yielding varieties can help the farmers in Pakistan to increase their revenue despite global population growth and changing international market patterns. At the Rice Research Institute, Kala Shah Kaku (RRI KSK), new, improved, high-yielding, extra-long grain lines with the qualities of early maturity, small stature, and good cooking with aroma are being developed through traditional breeding methods. The present study aimed to assess the genetic variability of these lines in terms of paddy yield and to discover superior high-yielding cultivars suitable for widespread cultivation. There were notable variations in paddy yield among the different entries in the pooled analysis. The highest average paddy yield (5010 Kg/ha) was seen in entry 10640-10-1-1-1, followed by entry 10684-3-1-2 (4990 Kg/ha) and PK 10434-6-2-1 (4550 Kg/ha) and suggested for general cultivation based on their mean paddy yield. A strong positive correlation was seen between the grain thickness grading of over 2.2 mm and the number of panicles per plant. The overall quality of the Uniform Yield Trials of Fine rice samples can be reported as excellent for PK 10306-15-5, PK PB-8 and PK 10678-2-1-1 over check Basmati-515. There will be a simultaneous increase in grain yield with improvements in these qualities.

Boron availability and fertilizer response of maize in soils from sub‐Saharan Africa

AbstractBackground and aimsLow boron (B) availability is associated with strongly weathered, coarse‐textured, and low organic matter soils, widespread in sub‐Saharan Africa (SSA). It is unknown to what extent B fertilization can increase maize yields in SSA. This study aims to understand the soil properties controlling B availability to field‐grown maize.MethodsBoron fertilizer omission trials with maize were executed at 15 sites in Kenya, Zambia, and Zimbabwe. Yield, B uptake, and soil parameters potentially relevant for B availability, including extractable soil B (hot water, 0.01 M CaCl2, and 0.43 M HNO3), were determined.ResultsSoil B pools were strongly intercorrelated and were positively correlated with organic carbon, suggesting the relevance of organic matter for soil B availability. Soil parameters described limited variation in B uptake and the yield response to B fertilization. Boron fertilization did not increase yields in any of the 15 sites but increased uptake in 11 sites. Yields were reduced through B fertilization in five sites, likely because B application induced toxicity. No clear critical soil or plant B concentrations indicating deficiency could be derived, but positive yield responses to B fertilization were absent with hot water B levels above 0.69 mg kg−1.ConclusionAssessing B fertilizer needs in maize grown in tropical soils based on soil or plant tissue concentrations remains challenging. Improving soil organic matter status could potentially alleviate B deficiency in crops when present. Recommendations are given to overcome the identified challenges associated with studying B availability in tropical soils.

The Response of Inorganic and Organic Fertilizers on Growth, Yield and Quality of Cluster Bean [Cyamopsis tetragonoloba (L.) Taub.] in the Village Chikkenahalli of Challakere Taluk, Chitraduraga District

Cluster bean is one of the significant yet underutilized leguminous vegetables belonging to family fabaceae. It is known by various names across the country such as gaur, chavli kaayi, gori kaayi, khutt, govar, and kothavare. A field experiment on cluster bean was carried out during the summer season of the year 2024 at the farm of P. L. Dodda Rangegowda in Chikkenahalli of Challakere taluk, Chitradurga district, Karnataka. The primary objectives of the study are to examine the effects of organic and inorganic fertilizers on the productivity and growth characteristics of cluster bean; to identify the advantages and disadvantages of these fertilizers in relation to productivity, soil fertility, and environment and further to review the effects of mixed organic and inorganic fertilizers on yield and soil fertility. The experiment was laid out in a randomized block design with four replications and five treatments which comprised of 100 percent organic (FYM and chicken manure), 100 percent inorganic (NPK), 50 percent organic + 50 percent inorganic, 100 percent organic + jeevamruta and control. The results revealed that, treatment T3 outperformed the others, showing the highest values for plant height, number of branches per plant, days to first flowering, days to first vegetable harvest, pod length, pod width, yield per plant, yield per plot, and yield per hectare, while the control recorded the lowest values. Soil properties such as pH, EC, SOC and NPK levels improved when combination of organic and inorganic fertilizers were applied together. Based on these results, it can be concluded that, the application of organic manures, along with chemical fertilizers, positively enhanced the vegetative growth, reproductive growth, yield, quality of cluster bean and soil parameters.

Enhancing the fruit yield and quality of pomegranate in a new niche area: Insights into site specific agronomic practices

The sustained higher profitability of a pomegranate orchard relies heavily on the production of a greater proportion of high-quality fruits, a goal achievable through the implementation of effective management practices. The objective of this study is to provide site-specific supplementary knowledge regarding the response of pomegranate plants to various management practices under arid conditions. With the aim of enhancing both marketable fruit yield and quality of pomegranate in arid regions, four separate and simultaneous experiments were conducted in the same orchard to evaluate (i) the response of planting materials derived from tissue culture, air layering, and cutting; (ii) the impact of crop (fruit) load; (iii) the response of crop regulation; and (iv) the application response of organo-mineral fertilizers containing potassium (OMF-K) and phosphorus (OMF-P). The results obtained for plant growth, fruit yield, and fruit quality did not exhibit significant differences among pomegranate plants raised through the three different methods of vegetative propagation. Striking results in terms of producing superior-grade fruits, higher marketable yield, and overall fruit quality were achieved with crop loads of 80 fruits per plant. Staggering the crop regulation from June to September effectively extended the harvesting season to four months, from the last week of November to March, with eventual benefit of reduced fruit cracking compared to the standard two-month harvesting period obtained from normal regulation. Soil application of the indigenously developed OMF-K in two equal splits, along with the recommended N and P through inorganic sources, significantly reduced fruit cracking (only 6.23%) compared to the recommended NPK through inorganic sources (26.9%), while maintaining similar physicochemical quality attributes.

Fertility, economic development, and remittances in post-communist times

ABSTRACT This study investigates fertility responses to remittances across developed and developing countries in post-communist times. We first collected fertility, remittances, and income statistics over the 1995–2020 period and created a new vulnerability index that identifies less economically developed states with high fertility rates and dependent on remittances. We then examined the global fertility effects of remittances between 1995 and 2015 via Ordinary Least Squares, Fixed Effects, and Instrumental Variable estimation methods. The baseline regression results suggest that the relationship between remittances and fertility rates of remittances-receiving countries is generally inverse. We also found that the fertility-reducing power of remittances is heterogeneous worldwide. To illustrate the findings, we constructed two heat maps for 196 countries. The first one depicts the distribution of the vulnerability index, and the second one is dedicated to variations in the fertility effects of remittances across countries based on the vulnerability index.

Nutritional profiles and fertilizer responsiveness of cold-adapted rice germplasm of Kashmir Himalayan region: creating a high-value germplasm repository for smart-breeding biofortified rice

Nutritional profiles and fertilizer responsiveness of cold-adapted rice germplasm of Kashmir Himalayan region: creating a high-value germplasm repository for smart-breeding biofortified rice

Response of Chemical Fertilisation on Six-year-old Oil Palm Production in Shambillo-Padre Abad- Ucayali

It was proposed to determine the response of chemical fertilization in the production of oil palm (Elaeis guineensis Jacq.) six years old in the area of Rio Negro Shambillo Padre Abad in order to have a sustainable and economic alternative of chemical fertilization in the field stage, which contributes to the survival of the palm and provides the necessary resistance against pests and diseases. A completely randomized block design (DBCA) was used with four repetitions and treatments, 96 plants / UE / treatment were used, the spacing was 9x9 in rows and plants. Results obtained indicate the treatments; T3 and T2 (16,54 – 15,48 kg / plant) obtained the highest averages by bunch weight, T1 and T3 (17,48 – 15,42 fruits / bunch) obtained the highest averages regarding number of fruit / bunch, T1 and T3 (13,93 – 11,59 to 45 cm ) obtained the highest averages for bunch length, T1 and T3 (7,33 – 5,52 cm) obtained the highest averages regarding fruit length, T1 and T3 (11.37 – 9.54 g) obtained the highest averages regarding fruit weight, T1 and T3 (10,46 – 10,37 kg) obtained the highest averages to yield per plant. The addition of chemical fertilizers or organic amendments increases the weight of the oil palm bunch, consequently the production in soils with medium, low fertility; chemical fertilization influences the number of clusters of oil palm produced on a given surface, any dose is used as an alternative to phosphorous fertilization in oil palm with a direct relationship between plant height and root length.

Forgotten Family: The Influence of Women and Children on the Nexus of Wage Earning and Demographic Change in England, 1260–1860

E. A. Wrigley identified the responsiveness of nuptiality and marital fertility to changes in male wages. Others have theorized the importance of women's decision-making in the timing of marriage, but without much empirical evidence. Combining new long-run series of annual wages for men, for married and single women, and for children with existing demographic data, the influence of women and children's remuneration on household formation is investigated. Women played a key role in the functioning of early modern preventive checks. High wages encouraged single women to delay marriage, reducing marital fertility. This counterbalanced the encouragement of nuptiality stimulated by high male earnings, which helped balance population and economic growth. Juvenile earnings had little influence on family formation, challenging links suggested in accounts of protoindustrialization or proletarianization. Demographic evidence suggests that economic circumstances contributed to the timing of medieval marriage, but poverty more often than prosperity prompted celibacy.

Multi-omics analysis of excessive nitrogen fertilizer application: Assessing environmental damage and solutions in potato farming

Potatoes (Solanum tuberosum L.) are the third largest food crop globally and are pivotal for global food security. Widespread N fertilizer waste in potato cultivation has caused diverse environmental issues. This study employed microbial metagenomic sequencing to analyze the causes behind the declining N use efficiency (NUE) and escalating greenhouse gas emissions resulting from excessive N fertilizer application. Addressing N fertilizer inefficiency through breeding has emerged as a viable solution for mitigating overuse in potato cultivation. In this study, transcriptome and metabolome analyses were applied to identify N fertilizer-responsive genes. Metagenomic sequencing revealed that excessive N fertilizer application triggered alterations in the population dynamics of 11 major bacterial phyla, consequently affecting soil microbial functions, particularly N metabolism pathways and bacterial secretion systems. Notably, the enzyme levels associated with NO3- increased, and those associated with NO and N2O increased. Furthermore, excessive N fertilizer application enhanced soil virulence factors and increased potato susceptibility to diseases. Transcriptome and metabolome sequencing revealed significant impacts of excessive N fertilizer use on lipid and amino acid metabolism pathways. Weighted gene co‑expression network analysis (WGCNA) was adopted to identify two genes associated with N fertilizer response: PGSC0003DMG400021157 and PGSC0003DMG400009544.

Ameliorating the response of slow-releasing nitrogen fertilizer on sustainable maize growth

The extensive utilization of nitrogen (N) fertilizers within maize cultivation systems has resulted in diminished nitrogen use efficiency (NUE) and contributed to nitrogen pollution on a global scale. To assess the ecological repercussions of excessive fertilization, it is imperative to elucidate both the nitrogen use efficiency and the fate of nitrogenous fertilizers upon application. The current research evaluated the potential of a newly developed slow-release nitrogen fertilizer on maize growth and its behavior in soil under controlled conditions. Six different levels of urea fertilizer (UF) and slow-release nitrogen fertilizer (SRNF) were administered within the field, representing 100%, 85%, and 70% of the recommended application rates. The slow-release nitrogen fertilizer (SRNF) exhibited superior performance regarding growth, yield and nutrient retention in comparison to urea fertilizer (UF). Moreover, minimal ammonia emissions were detected with the employment of the slow-release nitrogen fertilizer (SRNF), while other urea-based fertilizers proved inefficient in mitigating ammonia emissions, despite enhancing various growth and yield parameters. The efficiency in nutrient recovery followed a distinct pattern, with polymer-coated fertilizers demonstrating superiority. The plots treated with SRNF displayed significantly higher growth and yield characteristics compared to those treated with urea fertilizer. In terms of NH3 volatilization, the urea fertilizer (UF) treatment at 100% application rate showed higher emissions (1.99 mg g-1) after a 27-day incubation period, as opposed to the slow-release nitrogen fertilizer (SRNF) treatment (1.68 mg g-1). Leaching data indicated that urea fertilizer treatments led to greater losses of NO3-N (2.01 mg L-1) compared to SRNF treatments (0.88 mg L-1).

Fertility responses to short-term economic stress: Price volatility and wealth shocks in a pre-transitional settler colony

This paper examines the effects of short-term economic stress, captured by general price volatility and a negative wealth shock on short-run fertility behavior in the rural pre-transitional society of the Cape Colony. First, we link complete birth histories of settler women from the South African Families database to consumer price index data to examine the effect of price volatility on conceptions. Next, we link the same birth histories to slave owner and slave emancipation data to examine the effect of a negative wealth shock on conception. Upon slave emancipation in 1834, former slave owners received on average only between 40 and 50 % of the market value of their slaves as compensation, resulting in a substantial reduction in their wealth. Relying on event history models that look simultaneously at stopping and spacing, we do not find strong evidence in support of fertility control in response to general price volatility. We do find greater variance in birth interval lengths for former slaveholding households during and immediately after emancipation, suggesting that a negative wealth shock is associated with increased fertility limitation through postponement in this context.

Job insecurity and fertility: Evidence from massive lay-offs in urban China

We exploit a staggered reform of state-owned enterprises (SOEs) in the late 1990s in China to provide plausibly causal evidence that job insecurity has a first-order impact on fertility. Prior to the reform, unemployment rates were low and job security for SOE workers paralleled that of government employees. Post-reform, numerous SOE employees were laid off and their contracts were no longer permanent, but government employees continued to enjoy high levels of job security. We find that the reform caused SOE employees who retained their positions to delay having their first child by 0.718 years. The spillover effects are sizable: employees in the untargeted private sector delay starting a family by 0.387 years. Despite the importance of family lineage in China at the time, our findings indicate that the fertility response transcended mere birth timing adjustments, and decreased couples’ likelihood of having children. Specifically, the reform initially reduced the number of births by 8.4 % in the short run and had a more pronounced long-term effect on completed fertility at age 45.

Individual fertilization response with social status and crown characteristics for western hemlock (Tsuga heterophylla)

Due to their high variability, the growth responses of western hemlock ( Tsuga heterophylla (Raf.) Sarg.) stands to fertilization have been regarded as unresponsive or inconsistent. Tree-level fertilization response models for western hemlock were constructed to clarify the inconsistent stand-level responses, using extensive datasets from the United States and Canada. Tree growth in diameter and height, mortality, were assessed by fertilization, stand- and tree-level variables using generalized linear and nonlinear mixed-effects models. Western hemlock fertilization response was influenced not only by stand-level variables and application rates but also by tree social status and crown characteristics. Greater dominance and crown ratio in trees increased height growth responses but decreased diameter growth. The peak of fertilization effect on diameter growth was observed 3 years after application, while effect on height growth peaked at 6 years. Fertilization increased the overall mortality rate, but also ameliorated it for suppressed and steady-growing trees. These complicated fertilization responses of western hemlock may imply its tolerance and allocation strategy of resources at a given size and social status. The results highlight the importance of adopting a tree-level modeling approach to better understanding how western hemlock trees respond to fertilization, improving the accuracy of growth and yield prediction after fertilization.

Environmental Impact of Outdoor Cannabis Production.

Environmental impacts of cannabis production are of increasing concern because it is a newly legal and growing industry. Although a handful of studies have quantified the impacts of indoor production, very little is known about the impact of outdoor cannabis agriculture. Outdoor production typically uses little direct energy but can require significant fertilizer and other inputs due to dissipative losses via runoff and mineralization. Conversely, fertilizer high in nitrogen can be counterproductive, as it produces flowers with decreased cannabinoid content. This study has two aims: (1) To identify reduced-fertilizer regimes that provide optimal cannabis flower yields with reduced inputs and (2) to quantify how this shifts greenhouse gas emissions, resource depletion (fossil and metal), terrestrial acidification, and the eutrophication potential of outdoor cannabis production. Primary data from a fertilizer response trial are incorporated into a life-cycle assessment model. Results show that outdoor cannabis agriculture can be 50 times less carbon-emitting than indoor production. Dissemination of this knowledge is of utmost importance for producers, consumers, and government officials in nations that have either legalized or will legalize cannabis production.

Enhancement of southern flounder (Paralichthys lethostigma) sperm velocity and fertility by direct activation of sperm epidermal growth factor and adenylyl cyclase signaling pathways

Development of southern flounder commercial aquaculture is limited by poor sperm motility and fertility, but the underlying causes and mechanisms regulating sperm motility are unknown. In vitro treatment of southern flounder sperm with progestin hormones rapidly increases velocity (swimming speed), a major component of sperm motility, and also fertility through membrane progestin receptor alpha (mPRα) and increases in Acy (adenylyl cyclase)/cAMP signaling. The progestin-induced increase of Atlantic croaker sperm velocity is also mediated through epidermal growth factor receptor (Egfr) transactivation resulting in extracellular-regulated kinase 1/2 (Erk1/2) signaling, but its role in regulating southern flounder sperm velocity is unknown. The hypotheses that Egfr transactivation and Erk1/2 signaling mediates progestin-induced increases in sperm velocity and calcium levels in southern flounder, and that direct stimulation of sperm Egfr/Erk1/2 and Acy/cAMP pathways increases sperm fertility in strip spawning trials were tested in the present study. Golf, Egfr, Erk1/2, and protein kinase A were detected on southern flounder sperm by immunocytochemistry. Involvement of Egfr/Erk1/2 signaling in increasing sperm velocity and calcium levels was investigated by preincubating sperm with two EGFR inhibitors, AG1478, and AG825, a matrix metalloproteinase inhibitor, Ilomastat, and two ERK1/2 inhibitors, PD98059, and U0126, for 30 min prior to 1 min treatment with progestins. Sperm swimming speed was observed under a microscope after activation with a hyperosmotic medium and recorded for 1 min. Whereas treatment with the inhibitors did not alter basal sperm velocity and calcium levels, all of them significantly attenuated velocity and calcium increases in response to progestins. Treatment in vitro for 1 min with the Egfr agonist, recombinant human EGF (0.1 nM and 100 nM), mimicked the stimulatory effects of progestins on sperm velocity, the increase in calcium, and also fertility in a strip spawning trials with ovulated southern flounder eggs. The results suggest Egfr/Erk1/2 signaling is involved in sperm velocity and fertility responses to progestins in southern flounder. Direct in vitro treatment with the Acy activator, forskolin (10 μM) for 1 min mimicked the stimulatory action of progestins on sperm calcium levels, velocity, and fertility, suggesting that Acy/cAMP signaling also mediates increased sperm swimming speed and fertility. Importantly, both EGF and forskolin also directly stimulated southern flounder sperm velocity and fertility at the end of the reproductive season when sperm were no longer responsive to progestins. The results suggest that EGF and forskolin could potentially be used as pharmacological agents to enhance reproductive performance of male southern flounder broodstock.