Effects of water application intensity, drop size and water application amount on the characteristics of topsoil pores under sprinkler irrigation

Field experiments were carried out to study the effects of sprinkler irrigation on the characteristics of topsoil pores. Total soil porosity, capillary porosity, air-space porosity and porosities of different pore shapes were analyzed using images analysis of thin sections of soil samples. The experimental treatments included five water application intensities (5.3, 7.7, 11.0, 15.0 and 20.7 mm/h), five drop diameters (0.76, 1.28, 1.92, 3.18, 4.19 mm) and five water application amounts (9.0, 23.6, 37.5, 49.6, 59.4 mm). The compounding sprinkler system was used in the experiments of water application intensity and single sprinkler was used in the experiments of drop size and water application amount. The total porosity, air-space porosity and porosities of elongated pores have the similar decreasing tendency and pattern when water application intensity, drop diameter or water application amount increase. Capillary porosity, porosities of round and irregular pores have no obvious changing tendency. The decreasing porosities of the elongated pores and macropores are the main reasons for the decreasing of total porosity under sprinkler irrigation. To maintain soil structure in good conditions, the reasonable parameters would be considered for water application intensity, drop diameter and water application amount.

Effect of soil matric potential on the distribution of soil salt under drip irrigation on saline and alkaline land in arid regions

Field experiment was conducted to investigate the effect of soil matric potential on the distribution of soil salt under ridge-mulch drip irrigation on saline and alkaline land in arid regions. The experiment included three treatments, in which controlled the soil matric potential higher than -5 kPa (S1), -15 kPa (S2) and -25 kPa (S3), respectively, at 20 cm depth immediately under emitter. All treatments were repeated three times with the experimental plots following a complete randomized block design. Results show that the different salt ions have the different characteristics of transport and distribution under mulch drip irrigation. Na⁺ and Cl^- concentration easily leached by irrigation water is the lowest near the emitter and have an increasing trend of concentration far away from emitter. The leaching of Na⁺ and Cl^- is increasing with the increase of soil matric potential. There are linear relations of total dissolved solids to the concentration of Na⁺ and Cl^- in the experiment area, respectively. Mg²⁺, Ca²⁺ and HCO₃^- content are less influenced by soil matric potential, which have not obvious correlation with total dissolved solids and have relatively uniform distributions in the soil profile. The leaching of total dissolved solids mainly appears in the periods of the first drip irrigation with large amount of water on the same day after seeding and the later irrigation with high soil matric potential at seedling stage. There are less effects of irrigation water on the leaching of total dissolved solids at the latter stages of crop growth. The research results have a theory and application value for the water and salt regulation in soil and irrigation scheduling on saline and alkaline land

Characteristics of soil salinity and salt ions distribution in salt-affected field under mulch-drip irrigation in different planting years

In order to investigate the long-term effect of mulch-drip irrigation on the chemical properties of salt-affected soils by the method of time-space transformation. The characteristics of salinity and salt ions distribution in 0-150 cm soil profile in the fields with corn planted for one year and two years. At the same time, the uncropped saline waste land adjacent to the experimental site was taken as the control. The results show that the soil salinity, contents of individual salt ions, pH value, the ratio of Cl^- to SO₄^2- and sodium adsorption ratio (SAR) in 0-40 cm layer decreased gradually with the increase of planting years when the soil matric potential at 20 cm depth immediately under emitter is maintained higher than -10 kPa under mulch-drip irrigation. It indicates that soil environment is becoming better with the increase of planting years in 0-40 cm layer. Compared with uncropped saline waste land, contents of chloride and sodium, the ratio of Cl^- to SO₄^2- and SAR in the layer of below 40 cm under mulch-drip irrigation increase

Effects of Phosphate Application Rate on Grain Yield and Nutrition Use of Summer Maize under the Coastal Saline-Alkali Land

Saline-alkali soil is a major threat to global food security. Phosphorus (P) fertilizer is essential for crop growth and yield production. Nevertheless, the optimal phosphate fertilizer application rates for summer maize under coastal saline–alkali soil are still unclear. A field experiment with five phosphate application rates (0, 45, 90, 135, and 180 kg ha−1, referred to as T1, T2, T3, T4, and T5, respectively) was conducted during the 2018–2020 summer maize seasons study the effects of phosphate rates on the grain yield, biomass, and nitrogen (N), P and potassium (K) accumulation, and N, P, and K physiological efficiency (denoted as NPE, PPE and KPE, respectively). Results showed that P application notably improved maize grain and biomass yield, the total uptake of N, P, K, and NPE and KPE across three seasons. As the P addition increased to 135 kg ha−1, the grain yield achieved a maximum of 7168.4 kg ha−1, with an average NPE of 2.15 kg kg−1, PPE of 0.19 kg kg−1, and KPE of 1.49 kg kg−1. However, PPE continuously decreased with the input of phosphate. P application rates exceeding 135 kg ha−1 were not considered effective due to a decline in grain yield, nutrient uptake, and NPE. Furthermore, the effect of the planting season was significant on the total uptake of N and K, and the use efficiency of N, P, and K. TOPSIS revealed that a phosphate application rate of 90–135 kg ka−1 was the optimal pattern for maize production. These results may give a theoretical basis for the phosphate management of maize production in saline–alkali soil

Coupling Regulation of Root-Zone Soil Water and Fertilizer for Summer Maize with Drip Irrigation

Water scarcity is the most significant constraint for grain production in the North China Plain (NCP). Water-saving irrigation technology is a valuable tool for addressing the NCP’s water scarcity. Drip irrigation is considered as one of the most water-saving irrigation technologies. However, drip irrigation is not now commonly used in NCP field grain crops (particularly maize). Fertilizers are accurately administered to summer-maize root soil by recycling the drip-irrigation system of winter wheat. To increase the water and fertilizer-use efficiency of summer-maize fields, the coupling body of root-zone soil water and fertilizer for summer maize was thoroughly adjusted using a combination of emitter flow rate, irrigation quota, and fertilizer frequency. In this experiment, a split plot design with randomized blocks was employed. The primary plot was emitter flow rate (0.8 and 2.7 L/h), the subplot was irrigation water quota (120 and 150 m3/hm2, 1 hm2 = 10,000 m2), and the final plot was fertigation frequency (7, 14, and 28 days). The grain yield, water-use efficiency and fertilizer-use efficiency of summer maize were measured in this study. The results showed that grain yield and water-use efficiency (WUE) of the small-flow drip-irrigation treatment (emitter flow rate 1 L/h); the rates of grain yield increase were 8.2% and 13.3% and WUE were 3.5% and 8.0%, respectively. A higher irrigation quota can increase the yield of summer maize. The maximum yield and WUE were observed at the fertigation frequency of 7 days under small-flow drip-irrigation conditions. All comparisons and analyses showed that small-flow drip irrigation combined with high fertigation frequency could obtain higher yield and WUE in the NCP. This study proposes a new way to improve water and fertilizer utilization efficiency to achieve the goal of “increasing grain yield by fertilizing” and “adjusting the quality by fertilizing”, from the perspective of winter wheat–summer maize no-tillage annual rotation planting

Effects of Different Nitrogen Allocation Ratios and Period on Cotton Yield and Nitrogen Utilization

Choosing the proper fertilizer regime for a crop in a given location remains challenging to increase yield, profitability, environmental growth protection, and sustainability. However, the nutrient demand characteristics of cotton in the North China Plain are different at various growth stages. Therefore, we choose the local superior cotton variety (Lumian 532) with high yield as the material, in the present study, we assessed the cotton yield, biomass accumulation and distribution, nitrogen absorption and utilization efficiency, and other parameters by setting four nitrogen allocation ratios (3:5:2, 0:10:0, 3:7:0, and 0:7:3) when the nitrogen application rates were 0, 150, 220, and 300 kg hm−2. The results showed that when the nitrogen application rate was 300 kg hm−2, the growth index, biomass, nitrogen content, and yield of Lumian 532 were the highest, while the nitrogen partial productivity (12.2 and 12.8) was the lowest. When the nitrogen application rate was 220 kg hm−2 and the nitrogen allocation ratio was 3:5:2, the agronomic nitrogen use efficiency (3.2 and 3.5) and nitrogen physiological (24.8 and 25.0) was achieved. When the nitrogen application rate was 150 kg hm−2, the nitrogen partial productivity (20.6 and 20.9) was the highest. In conclusion, the biomass accumulation and distribution, nitrogen use efficiency, yield, and yield composition of Lumian 532 could be effectively regulated by appropriate nitrogen application rate and nitrogen allocation ratio. Therefore, to optimize the yield and improve the nitrogen use efficiency, the optimal nitrogen application rate of Lumian 532 was 220 kg hm−2, and the optimal nitrogen allocation ratio was 3:5:2 in the North China Plain. The results provided practical basis for nutrient demand, cotton yield and ecological protection in different growth stages of cotton in North China Plain

Decreasing Nitrogen Fertilizer Input Had Little Effect on Microbial Communities in Three Types of Soils

<div><p>In this study, we examined the influence of different nitrogen (N) application rates (0, 168, 240, 270 and 312 kg N ha^-1) on soil properties, maize (<i>Zea mays</i> L.) yields and microbial communities of three types of soils (clay, alluvial and sandy soils). Phospholipid fatty acid analysis was used to characterize soil microbial communities. Results indicated that N fertilization significantly decreased microbial biomass in both clay and sandy soils regardless of application rate. These decreases were more likely a result of soil pH decreases induced by N fertilization, especially in the sandy soils. This is supported by structural equation modeling and redundancy analysis results. Nitrogen fertilization also led to significant changes in soil microbial community composition. However, the change differences were gradually dismissed with increase in N application rate. We also observed that N fertilization increased maize yields to the same level regardless of application rate. This suggests that farmers could apply N fertilizers at a lower rate (i.e. 168 kg N ha^-1), which could achieve high maize yield on one hand while maintain soil microbial functions on the other hand.</p></div

Downscaling TRMM Monthly Precipitation Using Google Earth Engine and Google Cloud Computing

Accurate precipitation data at high spatiotemporal resolution are critical for land and water management at the basin scale. We proposed a downscaling framework for Tropical Rainfall Measuring Mission (TRMM) precipitation products through integrating Google Earth Engine (GEE) and Google Colaboratory (Colab). Three machine learning methods, including Gradient Boosting Regressor (GBR), Support Vector Regressor (SVR), and Artificial Neural Network (ANN) were compared in the framework. Three vegetation indices (Normalized Difference Vegetation Index, NDVI; Enhanced Vegetation Index, EVI; Leaf Area Index, LAI), topography, and geolocation are selected as geospatial predictors to perform the downscaling. This framework can automatically optimize the models&rsquo; parameters, estimate features&rsquo; importance, and downscale the TRMM product to 1 km. The spatial downscaling of TRMM from 25 km to 1 km was achieved by using the relationships between annual precipitations and annually-averaged vegetation index. The monthly precipitation maps derived from the annual downscaled precipitation by disaggregation. According to validation in the Great Mekong upstream region, the ANN yielded the best performance when simulating the annual TRMM precipitation. The most sensitive vegetation index for downscaling TRMM was LAI, followed by EVI. Compared with existing downscaling methods, the proposed framework for downscaling TRMM can be performed online for any given region using a wide range of machine learning tools and environmental variables to generate a precipitation product with high spatiotemporal resolution