The adaptability and irrigation constraints analysis of the WOFOST model for grain production in the Songhua River Basin.

BACKGROUND: The Songhua River Basin, a vital grain-producing area in China, faces challenges due to the uneven distribution of water resources and the intensive water demands of agriculture. To enhance agricultural development and effectively manage water scarcity, it is essential to identify the water-saving potential of major staple crops - corn, wheat, and rice. This study enhances the World Food Studies (WOFOST) model by refining the day of year for the developmental vegetative stage (DVS), thereby improving the representation of phenological stages for spring maize, spring wheat, and rice within the model. This refinement offers a detailed analysis of the potential and rainfed yields. RESULTS: The results from the modified WOFOST model show promising simulation outcomes for the biomass and yield of maize, wheat, and rice, with Nash-Sutcliffe efficiency (NS) and index of agreement (IoA) values all exceeding 0.7. An analysis of photothermal potential yields (Yp) and rainfed yields (Yr) revealed minimal differences in yields for spring maize and rice across various rainfall frequencies. Specifically, the average photothermal utilization rates (LTs) are 93.57% for maize and 85.25% for rice. In contrast, the rainfed yield for wheat is lower than its photothermal yield, with an LT of 43.66%. CONCLUSIONS: These findings suggest that in the Songhua River Basin, maize and rice offer greater potential for water conservation compared to wheat. It is recommended to judiciously reduce irrigation during the growing seasons of spring maize and rice to help alleviate agricultural water use pressures. © 2024 Society of Chemical Industry.

Effects of irrigation methods and salinity on CO2 emissions from farmland soil during growth and fallow periods.

Drip irrigation and brackish water irrigation are considered to be the two main ways to alleviate the current shortage of agricultural freshwater resources and have been widely used in countries around the world. Our purpose is to evaluate the effects of different irrigation methods (flood irrigation and drip irrigation) and irrigation water salinities (1.1 g·L-1, 2.0 g·L-1, 3.5 g·L-1, and 5.0 g·L-1) on the soil CO2 emissions during the growth and fallow periods of spring maize. Therefore, a two-year field experiment was conducted in Hetao Irrigation District in China from 2017 to 2019. The results showed that compared with flood irrigation, drip irrigation significantly decreased the soil CO2 emissions in the growth period. After irrigation with a salinity of 5.0 g·L-1, the soil moisture was the highest because the plant water absorption was inhabited by soil salt, and the soil CO2 emissions were also promoted during the growth period. Irrigation method and irrigation water salinity had no effect on the soil CO2 emissions in the fallow period. Soil temperature, moisture and inorganic nitrogen content were the main factors affecting the daily CO2 emission flux. The soil CO2 emissions during the growth period accounted for more than 83.93% of the annual soil emissions. Based on the goal of saving freshwater resources, ensuring soil safety, reducing soil CO2 emissions and increasing the size of the carbon pool, adoption of drip irrigation with 2.0 g·L-1 brackish water could be adopted to ensure the sustainable development of local agriculture.

Finding the optimal fertilizer type and rate to balance yield and soil GHG emissions under reclaimed water irrigation.

Water and inorganic nitrogen fertilizer have a notable impact on crop yield and greenhouse gas (GHG) emissions from soil. Reclaimed water (RW) is widely used for irrigation when there are shortages of water resources. It is very important to control yield and greenhouse gas emissions by fertilization under reclaimed water irrigation (RWI). The study consisted of a continuous test that evaluated three types of fertilizer treatments (urea, amine, and slow-release fertilizer) and a no-fertilizer treatment under three-year RWI and four fertilizer levels (150, 200, 250 and 300 kg.N.ha-1) under one-year RWI to determine the best fertilizer to support maize production and reduce GHG (CO2 and N2O) emissions from soil; further, the applicability of RWI in the DNDC model was verified. For many years, GHG emissions under RWI showed an increasing trend, but the effect was not significant. A strong correlation was found between the GHG emissions flux and fertilizer amount, and a threshold fertilization amount existed between 220 and 260 kg.N.ha-1 that minimized yield-scaled N2O emissions and the ratio of GHG cumulative emission to yield (GHG/Y). The results indicated that the optimal amounts of SF and UF under RWI were 240 and 225 kg.N.ha-1 by second-order equation and the DNDC model, respectively, and the rate better balanced the yield and GHG emissions.

Effects of fertilizer types and water quality on carbon dioxide emissions from soil in wheat-maize rotations.

The use of fertilizers as addition inputs in agricultural systems can increase the yield of wheat and maize, while also stimulating the emission of carbon dioxide from soil that the main man-made greenhouse gas. Our objectives focused on the impact of different types of synthetic fertilizers and water quality. The purposes were to determine the feasibility of using wasted water for irrigation and to relate CO2 fluxes to the yield of maize and wheat, as well as to select the best fertilizer type with low CO2 emission and high yield. The experiment consisted of a double factors test focusing on four forms of fertilizer (urea, amine and slow release fertilizer) and the quality of water (reclaimed water and underground water). The results showed that the reclaimed water was not significant on the CO2 discharge rate, the maize-wheat yield or the soil properties in 2014 or 2015; however, the CO2 emission increased slightly in 2015. Focusing on fertilizer treatments, the reclaimed water & amine fertilizer treatment (CAF) that had higher cumulative CO2 emissions was 32.75 t·ha-1 in 2014 and 33.86 t·ha-1 in 2015. According to the ratio CO2/Y, the slow released fertilizer that reduces CO2 emissions and keeps the yield high is the preferred choice.