Koffi Djaman

Irrigation management is essential for successfully cultivating Chile peppers (Capsicum spp.), as it influences plant yield, fruit quality, and susceptibility to soil-borne diseases. This study investigates the effects of various sprinkler irrigation regimes on different Chile pepper varieties to optimize water use efficiency and enhance overall production. The varieties included in the study are ‘TAM Mild Jalapeno’, ‘Anaheim’, ‘Sandia’, ‘NM#6’, ‘California Wonder’, and ‘Red Knight’. Field experiments were conducted at the Agricultural Science Center in Farmington during the 2024 and 2025 growing seasons. A split-plot design with three replicates was employed to assess the effects of varying irrigation levels (100%, 80%, and 60% ET), which corresponded to 0%, 20%, and 40% water savings, respectively. Each plot comprised three rows of 10 plants, with 0.762 m between rows and 0.305 m between plants. In both 2024 and 2025, the amounts of applied irrigation and total water supplied varied across the irrigation treatments, with greater depths under the 100% ET regime and progressively lower amounts at 80% ET and 60% ET. Irrigation Water Use Efficiency (IWUE) values varied from 4.06 kg m⁻³ in ‘NM#6’ to 9.57 kg m⁻³ in ‘TAM Mild Jalapeno’ in 2024. In 2025, IWUE values ranged from 4.62 kg m⁻³ in ‘California Wonder’ to 8.76 kg m⁻³ in ‘TAM Mild Jalapeno’. On average, ‘TAM Mild Jalapeno’ consistently had the highest IWUE across both years, while ‘NM#6’ had the lowest. Evapotranspiration Water Use Efficiency (ETWUE) values ranged from 5.41 kg m⁻³ in ‘NM#6’ to 12.13 kg m⁻³ in ‘TAM Mild Jalapeno’ in 2024. In 2025, ETWUE values ranged from 6.99 kg m⁻³ in ‘California Wonder’ to 12.82 kg m⁻³ in ‘TAM Mild Jalapeno’. On average, ‘TAM Mild Jalapeno’ consistently had the highest ETWUE across both years, while ‘NM#6’ had the lowest. Results indicated that both ‘TAM Mild Jalapeno’ and ‘California Wonder’ achieved the highest marketable yields in 2024, while ‘TAM Mild Jalapeno’ and ‘Red Knight’ had the greatest marketable yields in 2025. Moderate deficit irrigation (20% water savings) maintained or improved marketable yield and water use efficiency. In contrast, a 40% water savings strategy led to significant reductions in both yield and plant growth. ‘TAM Mild Jalapeno’ exhibited the greatest adaptability to water-limited conditions, consistently achieving the highest irrigation and evapotranspiration water use efficiency. Conversely, ‘California Wonder’ was more sensitive to severe water deficits.

The response of chile peppers (Capsicum spp.) to different irrigation systems is an important factor affecting crop yield, quality parameters, and resistance to soil-borne diseases. The choice of irrigation method significantly impacts fruit size development, water-use efficiency, and overall crop production. Research shows that proper irrigation management can increase yields, improve physiological response, and reduce the incidence of Phytophthora blight, a major disease caused by Phytophthora capsici. However, over-irrigation directly harms chile peppers, causing waterlogging, which, together with increasing weed spreads, creates favorable conditions for P. capsici to grow and increase disease susceptibility. Conversely, under-irrigation can induce drought stress that weakens chile peppers and increases their vulnerability to P. capsici. Although the pathogen cannot thrive or spread in dry soils, severely stressed plants become highly susceptible when even brief periods of moisture occur—such as from dew, light rainfall, or a short irrigation event—creating favorable conditions for infection. In addition, lack of proper timing and insufficient irrigation frequency adversely affect fruit quality characteristics, including capsaicin content (spiciness), color, and nutrient composition. Water stress is extremely damaging because it can reduce the biomass of plants, delay flowering, reduce fruit size, or cause significant yield loss. Considering the importance of water management in chile pepper cultivation and optimizing irrigation systems is important to ensure high-quality crops. Disease susceptibility and effects of different irrigation systems, including inadequate irrigation and excessive irrigation, have been reviewed, with an emphasis on the impact of these irrigation methods on plant growth and yield quality, and on Phytophthora blight. This review aims to provide insights into the importance of irrigation management for sustainable and effective chile pepper production and disease control.

Increasing water scarcity for agricultural irrigation demands options to maximize yield with available water. Alfalfa (Medicago sativa) is a valuable crop in arid and semiarid regions and is considered a major user of irrigation water. Consequently, an area of established alfalfa was center-pivot-irrigated over two years according to one of four irrigation regimes, each with three replicates as strip plots. These were started after the last of the six harvests of the year, after seeding: winter-irrigated and throughout the growing season (winter full), winter-irrigated and terminated after the 4th harvest (winter limited), irrigated from mid-April, when canal water typically becomes available, and throughout the remainder of the growing season (season full), or typically-irrigated until the 4th harvest (season limited). Annual dry matter yield (DMY) was increased using winter irrigation compared to season-only irrigation (10.34, 8.94, 8.67, and 6.54 Mg ha⁻¹ for winter full, winter limited, season full, and season limited, respectively, p < 0.0001, SEM 0.45). Irrigation termination after the fourth harvest with no winter irrigation significantly reduced annual applied water use efficiency (AAWUE) compared to all other treatments (9.08, 8.59, 8.82, and 7.38 kg DMY ha⁻¹ mm⁻¹ for winter full, winter limited, season full, and season limited, respectively; p < 0.0098, SEM = 0.38). Winter irrigation to fill the soil profile, followed by late summer irrigation termination, is feasible for increasing alfalfa productivity over season-only irrigation.

Analysis of reference evapotranspiration (ET₀) trends is essential for understanding the impacts of climate change on water resources. Thus, despite the continuous rise in temperatures, a decrease in evapotranspiration is noted in some parts of the world. This contrast is called the “evaporation paradox” and is thought to be related to the variation in wind speed, relative humidity and solar radiation. The objective of this work is to analyze the annual and seasonal trends of ET₀ and climate variables at the scale of the Senegal, Gambia and Casamance river basins. The reanalyze data of NASA/POWER are used over the period 1984–2019. Mann Kendall's test and Sen slope were used to analyze trends in ET₀ and climate variables. Results show that on annual scale, ET₀ increases significantly in 32 % of the Senegal basin and decreases in less than 1 % of it. In contrast, in the Casamance and Gambia basins, the annual ET₀ drops by 65 % and 18 %, respectively. On an annual scale, temperature and relative humidity show an increasing trend over all basins while wind speed and radiation decrease significantly. This confirms the existence of the “evaporation paradox” in the three basins. This phenomenon is explained by the increase in relative humidity and the decrease in wind speed and solar radiation.

This study aimed to measure maize (Zea mays) plant nutrient content and nutrient removal in grain, and to evaluate the residual soil nitrogen, phosphorus, and potassium as impacted by planting date and density. Field experiments were conducted to evaluate six plant densities and seven planting dates using a split-split plot design with three replications. Besides the crop growth and yield parameters, six plants were collected at the maturity and soil was sampled from each plot for nutrient analysis. Plant N, P, and K concentrations varied with planting date and density and within the ranges of 0.6–1.024%, 0.054–0.127%, and 0.75–1.71%, respectively. Grain N, P, and K concentrations decreased with plant density and varied from 1.059 to 1.558%, 0.20 to 0.319%, and 0.29 to 0.43%, respectively. Soil residual nutrient varied with depth, planting density and date. Residual N concentration in the topsoil varied from 0.6 to 37.2 mg kg^-1 in 2019 and from 1.5 to 11.2 mg kg^-1 in 2020 and was high under the last two planting dates. Soil residual N concentration was higher in the second layer than in the topsoil. The N concentration in the third layer varied from 0.1 to 33.2 mg kg^-1 and was impacted by plant density. Topsoil P did not vary among planting dates and densities. The second and third soil layers P concentration was not affected. There was 83% increase in topsoil K in 2020 compared to 2019, and a decrease of 65 and 23% in soil K was observed in the second and third soil layers, respectively. For maize production system sustainability, future research should use a holistic approach investigating the impact of planting date, plant density on crop growth, yield, nutrient uptake and remobilization, and soil properties under different fertilizer rates to develop the fertilizer recommendation for maize while reducing the environmental impact of the production system.

Irrigation and nitrogen management are crucial for sustainable potato (Solanum tuberosum L.) production. A field experiment was conducted during the 2022 and 2023 growing seasons at Farmington, New Mexico, to evaluate the performance of two chip potato varieties (Lamoka and Waneta) under three irrigation regimes (full irrigation (FI), 20% deficit irrigation (DI) and 40% DI) and seven nitrogen fertilizer rates (0, 60, 115, 170, 220, 280, and 340 kg N/ha). The treatment combinations of irrigation regimes, nitrogen rates, and varieties were arranged in a split–split plot design with three replications as main plot, sub-plot, and sub-sub plot, respectively. The two-year results showed that irrigation regimes had the most significant effect on plant growth, physiology, and tuber yield of the potato varieties. For both Lamoka and Waneta, the plant height and canopy cover were lower under 40% DI than under 20% DI and FI treatments. The SPAD meter values were higher under 40% DI, followed by 20% DI and FI treatments, whereas the stomatal conductance was higher under FI, followed by 20% DI and 40% DI during both growing seasons. Regardless of nitrogen rates and variety, a 20% water-saving irrigation strategy reduced the total tuber yield by 4.5% and 22.1% in the 2022 and 2023 growing seasons, respectively, while the 40% water-saving irrigation strategy reduced total tuber yield by 36.8% and 58.2% in the 2022 and 2023 growing seasons, respectively, as compared to full irrigation. Shifting from full irrigation to 20% DI could save 711.2 to 1036.3 m³/ha of irrigation water. For Lamoka, the highest total tuber yield was obtained with 60 kg N/ha under 20% DI and 220 kg N/ha under FI in 2022 and 2023, respectively. For Waneta, the highest total tuber yield was obtained with 115 kg N/ha under 20% DI and 170 kg N/ha under FI in 2022 and 2023, respectively. Maximum water use efficiency (WUE) was obtained at 60 kg N/ha with 20% DI for both Lamoka and Waneta in 2022, while maximum WUE was obtained at 220 kg N/ha under FI for Lamoka and at 170 kg N/ha for Waneta in the 2023 season. The maximum nitrogen use efficiency (NUE) was achieved with 60 kg N/ha under 20% DI for both varieties during both growing seasons. Thus, for sustainable irrigation and nitrogen management, the application of a 20% deficit irrigation strategy with a lower nitrogen rate (60 to 170 kg N/ha) could be the best option to improve WUE and NUE with minimal tuber yield reduction. Our study suggested that 40% deficit irrigation would not be beneficial as compared to both full irrigation and 20% water-saving irrigation.