Dryland irrigation increases accumulation rates of pedogenic carbonate and releases soil abiotic CO2

Agricultural fields in drylands are challenged globally by limited freshwater resources for irrigation and also by elevated soil salinity and sodicity. It is well known that pedogenic carbonate is less soluble than evaporate salts and commonly forms in natural drylands. However, few studies have evaluated how irrigation loads dissolved calcium and bicarbonate to agricultural fields, accelerating formation rates of secondary calcite and simultaneously releasing abiotic CO2 to the atmosphere. This study reports one of the first geochemical and isotopic studies of such “anthropogenic” pedogenic carbonates and CO2 from irrigated drylands of southwestern United States. A pecan orchard and an alfalfa field, where flood-irrigation using the Rio Grande river is a common practice, were compared to a nearby natural dryland site. Strontium and carbon isotope ratios show that bulk pedogenic carbonates in irrigated soils at the pecan orchard primarily formed due to flood-irrigation, and that approximately 20–50% of soil CO2 in these irrigated soils is calcite-derived abiotic CO2 instead of soil-respired or atmospheric origins. Multiple variables that control the salt buildup in this region are identified and impact the crop production and soil sustainability regionally and globally. Irrigation intensity and water chemistry (irrigation water quantity and quality) dictate salt loading, and soil texture governs water infiltration and salt leaching. In the study area, agricultural soils have accumulated up to 10 wt% of calcite after just about 100 years of cultivation. These rates will likely increase in the future due to the combined effects of climate variability (reduced rainfall and more intense evaporation), use of more brackish groundwater for irrigation, and reduced porosity in soils. The enhanced accumulation rates of pedogenic carbonate are accompanied by release of large amounts of abiotic CO2 from irrigated drylands to atmosphere. Extensive field studies and modelling approaches are needed to further quantify these effluxes at local, regional and global scales.

Adapting Root Distribution and Improving Water Use Efficiency via Drip Irrigation in a Jujube (Zizyphus jujube Mill.) Orchard after Long-Term Flood Irrigation

Jujube tree yields in dryland saline soils are restricted by water shortages and soil salinity. Converting traditional flood irrigation to drip irrigation would solve water deficit and salt stress. The root distribution reacts primarily to the availability of water and nutrients. However, there is little information about the response of jujube roots to the change from flood irrigation to drip irrigation. In this context, a two–year experiment was carried out to reveal the effects of the change from long–term flood irrigation to drip irrigation on soil water, root distribution, fruit yield, and water use efficiency (WUE) of jujube trees. In this study, drip irrigation amounts were designed with three levels, i.e., 880 mm (W1), 660 mm (W2), 440 mm (W3), and the flood irrigation of 1100 mm was designed as the control (CK). The results showed that replacing flood irrigation with drip irrigation significantly altered soil water distribution and increased soil moisture in the topsoil (0–40 cm). In the drip irrigation treatments with high levels, soil water storage in the 0–60 cm soil layer at the flowering and fruit setting, and fruit swelling stages of jujube trees increased significantly compared with the flood irrigation. After two consecutive years of drip irrigation, the treatments with higher irrigation levels increased root length density (RLD) in 0–60 cm soil depth but decreased that in the 60–100 cm depth. In the horizontal direction, higher irrigation levels increased RLD in the distance of 0–50 cm, while reducing RLD in the distance of 50–100 cm. However, the opposite conclusion was obtained in W3 treatment. Additionally, in the second year of drip irrigation, W2 treatment (660 mm) significantly improved yield and WUE, with an increasing of 7.6% for yield and 60.3% for WUE compared to the flood irrigation. In summary, converting flood irrigation to drip irrigation is useful in regulating root distribution and improving WUE, which would be a promising method in jujube cultivation in arid regions.

Phenological behaviour of gobhi sarson (Brassica napus L.) and thermal indices as influenced by drip irrigation and fertigation schedules under semi-arid subtropical condition of Punjab

A field experiment was conducted during rabi 2016-17 and 2017-18, at the Research Farm of Department of Agronomy, Punjab Agricultural University, Ludhiana, to study the phenological behaviour of gobhi sarson (Brassicanapus L.) and thermal indices as influenced by drip irrigation (60, 80 and 100% of cumulative pan-evaporation, CPE) and fertigation schedules (60, 80 and 100 % recommended dose of fertilizers, RDF) in comparison with conventional flood irrigation and manual application of fertilizers i.e. absolute control. The pooled data revealed that Brassica irrigated through drip at 100 % of CPE took maximum number of days to attain 50% flowering, 50% siliqua formation and physiological maturity, followed by 80 and 60% of CPE. Higher fertigation levels also delayed the number of days taken to attain various phenological stages. Maximum seed yield was observed at 100% of CPE with 100% RDF which was statistically at par with 100% of CPE with 80% RDF and 80% of CPE with 80 or 100% RDF, but significantly higher than absolute control. Maximum accumulation of heat units along with heat use efficiency (1.49 kg grains ha-1 °C day hour-1) was also obtained at 100% of CPE with 100% RDF.

The potential importance of soil denitrification as a major N loss pathway in intensive greenhouse vegetable production systems

Background About 30 % of vegetables in China are produced in intensively managed greenhouses comprising flood irrigation and extreme rates of nitrogen fertilizers. Little is known about denitrification N losses. Methods Soil denitrification rates were measured by the acetylene inhibition technique applied to anaerobically incubated soil samples. Four different greenhouse management systems were differentiated: Conventional flood irrigation and over-fertilization (CIF, 800 kg N ha−1, 460 mm); CIF plus straw incorporation (CIF+S, 889 kg N ha−1, 460 mm); Drip fertigation with reduced fertilizer application rates (DIF, 314 kg N ha−1, 190 mm); DIF plus straw incorporation (DIF+S, 403 kg N ha−1, 190 mm). Soil denitrification was measured on nine sampling dates during the growing season (Feb 2019-May 2019) for the top-/ subsoil (0 – 20/ 20- 40 cm) and on three sampling dates for deep soils (40-60/ 80-100 cm). Data was used to constrain N-input-output balances of the different vegetable production systems. Results Rates of denitrification were at least one magnitude higher in topsoil than in sub- and deep soils. Total seasonal denitrification N losses for the 0 – 40 cm soil layer ranged from 76 (DIF) to 422 kg N ha−1 (CIF+S). Straw addition stimulated soil denitrification in top- and subsoil, but not in deep soil layers. Integrating our denitrification data (0-100 cm) with additional data on N leaching, N2O emissions, plant N uptake, and NH3 volatilization showed, that on average 50 % of added N fertilizers are lost due to denitrification. Conclusions Denitrification is likely the dominant environmental N loss pathway in greenhouse vegetable production systems. Reducing irrigation and fertilizer application rates while incorporating straw in soils allows the reduction of accumulated nitrate.

A WiFi-Based Sensor Network for Flood Irrigation Control in Agriculture

The role of agriculture in society is vital due to factors such as providing food for the population, is a major source of employment worldwide, and one of the most important sources of revenue for countries. Furthermore, in recent years, the interest in optimizing the use of water resources has increased due to aspects such as climate change. This has led to the introduction of technology in the fields by means of sensor networks that allow remote monitoring and control of cultivated lands. In this paper, we present a system for flood irrigation in agriculture comprised of a sensor network based on WiFi communication. Different sensors measure atmospheric parameters such as temperature, humidity, and rain, soil parameters such as humidity, and water parameters such as water temperature, salinity, and water height to decide on the need of activating the floodgates for irrigation. The user application displays the data gathered by the sensors, shows a graphical representation of the state of irrigation of each ditch, and allows farmers to manage the irrigation of their fields. Finally, different tests were performed on a plot of vegetables to evaluate the correct performance of the system and the coverage of the sensor network on a vegetated area with different deployment options.

Assessment of Cob Characteristics of Sweet Corn on Sandy Soils under Different Irrigation Methods

Drip irrigation is an incredibly efficient watering method that slowly delivers water directly to a plants root system, through a network of small pipes. This minimizes conventional losses such as deep percolation, runoff and soil erosion. A few low cost automation systems were developed and evaluated their performance with drip irrigation on sweet corn. Compared to flood irrigation and paired row drip irrigation, single row drip irrigation produced better results. The results indicated that the number of kernel rows per cob, number of kernels per cob, length and diameter of the cob and individual fresh cob weight were observed to be more in single row as compared to flood irrigation and paired row drip irrigation systems. The yield response was also observed to be best in soil moisture sensor based irrigation with single row spacing.

Nitrogen application rate and timing management for improved grain quality parameters of wheat crop

Nitrogen use efficiency under flood irrigation system is generally low (30%) in field crops, which is one of the fundamental factors of high production cost in the developing countries. Optimum rate and timing of N-application is otherwise important to harvest good quality grain for backing in the recent climate change scenario. Optimum N-rate (NAR) corresponds with the application timing (NAT) has resulted in good quality grains. Aim of the study was to focus on spring wheat grain quality and N use efficiency (NUE) with NAR {i.e., 0, 100, 120, 140 and 160 kg ha-1) and NAT (i.e., 100% at sowing (NAR1), 50% at sowing and 50% at tillering (NAT2), 25% at sowing, 50% at tillering and 25% at booting (NAT3) and 25% at sowing, 25% at tillering and 50% at booting (NAT4)}. Treatment impacts were investigated focusing grain yield, grain-N, and quality parameters (i.e., crude protein, gluten, amylose and amylopectin). Experiment was a randomized complete block, in three replications, conducted at Agronomy Res. Farm of the University of Agric. Peshawar in 2016-17 and repeated in 2017-18. Results showed the highest NUE in100 kg N ha-1, followed by a decreasing rate (p<0.05) for every next N-increment. While averaged on N-rates, the highest NUE observed in NAT3 which did not differ fromNAT4 but decreased (p<0.05) for treatment NAT2 with lowest for theNAT1. Pakhtunkhuwa-2015 showed higher NUE among the varieties. Grain-N, grain yield, gluten and amylose did not differ with NAR 140 and 160 kg ha-1 as well as for the NAT3 and NAT4 but decreased for NAT2 and the lowest was noted for NAT1. The N-content of wheat grain was highest in Pakhtunkhuwa-2015, followed by Pirsabak-2015 and the lowest in DN-84. Nonetheless, grain amylopectin showed a reduction with increasing NAR and/or split N-applications from one to two and/or three doses. Cultivars did not show any changes in the amylopectin. It is concluded that in recent climate changes where flood irrigation system is practiced, three N-splits (NAT3 or NAT4) resulted higher quality grains with140 kg N ha-1 to wheat crop

Climate-smart agriculture practices influence weed density and diversity in cereal-based agri-food systems of western Indo-Gangetic plains

Climate-smart agriculture (CSA)-based management practices are getting popular across South-Asia as an alternative to the conventional system for particular weed suppression, resources conservation and environmental quality. An 8-year study (2012–2013 to 2019–2020) was conducted to understand the shift in weed density and diversity under different CSA-based management practices called scenarios (Sc). These Sc involved: Sc1, conventional tillage (CT)-based rice–wheat system with flood irrigation (farmers’ practice); Sc2, CT-rice, zero tillage (ZT)-wheat–mungbean with flood irrigation (partial CA-based); Sc3, ZT rice–wheat–mungbean with flood irrigation (partial CSA-based rice); Sc4, ZT maize–wheat–mungbean with flood irrigation (partial CSA-based maize); Sc5, ZT rice–wheat–mungbean with subsurface drip irrigation (full CSA-based rice); and Sc6, ZT maize–wheat–mungbean with subsurface drip irrigation (full CSA-based maize). The most abundant weed species were P. minor > A. arvensis > M. indicus > C. album and were favored by farmers’ practice. However, CSA-based management practices suppressed these species and favored S. nigrum and R. dentatus and the effect of CSAPs was more evident in the long-term. Maximum total weed density was observed for Sc1, while minimum value was recorded under full CSA-based maize systems, where seven weed-species vanished, and P. minor density declined to 0.33 instead of 25.93 plant m−2 after 8-years of continuous cultivation. Full CSA-based maize–wheat system could be a promising alternative for the conveniently managed rice–wheat system in weed suppression in north-west India.

Poultry Manure Induced Garden Eggs Yield and Soil Fertility in Tropical and Semi-Arid Sandy-Loam Soils

Synthetic nitrogen fertilizer use comes with unsustainable financial and environmental costs, making it not attractive to small-scale and organic farmers. Poultry manure (PM) when available is a primary fertilizer source for small-scale and organic farmers but there is still limited research on its effects of specific crops and soil fertility under specific practices. The study investigated PM effects on garden egg in three seasons in Ghana and PM effects soil fertility in sandy-loam soils of Arizona after three years under flood irrigation and no-till. The PM application improved garden egg growth (dry matter by 73%) and increased yield by 66% in slightly acidic sandy-loam tropical soils, which could be related to soil mineral improvement. In the semi-arid soil, three years PM application increased cation exchange capacity (41%), P (471%), K (18%), S (244%), Ca (45%), Mg (31%), Zn (5%) and Mn (19%) with reduction in nitrate (−26%), Fe (−38%) and Cu (−11%). The reduction in the nitrate and Fe in the semi-arid Arizona cropland could be associated to flood irrigation and high soil pH, respectively. To gain the full potential from PM applications, best management practice is recommended to reduce nitrate leaching.

Model Validation of Aqua Crop for Brinjal (Solanum melongena) Crop at Madakasira Region, Anantapur District, Andhra Pradesh

Crop simulation models plays a vital role for estimating the effects of soil, water, nutrients on grain and biomass yields and water productivity of different crops. Among the various crop simulation models, Aqua Crop model was adopted for the predicting the crop water requirement in the Madakasira region, Anantapur district, Andhra Pradesh. The Brinjal crop was selected for the study and was irrigated through two different methods i.e., drip and flood irrigation. The model generated the crop yield and crop water requirement for the drip and flood irrigation of Brinjal crop was compared with the actual field results of crop yield and crop water requirement. The simulated crop yield and crop water requirement for the Brinjal crop under flood irrigation was 5.23 t/ha and 326 mm. The actual crop yield and crop water requirement for the Brinjal crop under flood irrigation was 4.2 t/ha and 335 mm. The simulated crop yield and crop water requirement for the Brinjal crop under Drip irrigation was 5.76 t/ha and 318.3 mm. The actual crop yield and crop water requirement for the Brinjal crop under drip irrigation was 4.8 t/ha and 290 mm. From the results, it was clear that the model simulated the actual conditions of the crop. The benefit cost ratio was done for the experimental field data which clearly shows that the crop yield under drip irrigation has achieved the higher cost benefit ratio. Therefore, Aqua Crop model was suitable for simulating the crop conditions under any circumstances.