Irrigation Inputs Research Articles

Irrigation on the move: How transient farming partnerships facilitate the expansion of smallholder irrigation along ephemeral rivers in dryland areas of Kenya

Irrigation is commonly viewed as an activity fixed in time and place requiring permanent infrastructure. However, smallholder farmers in Sub-Saharan Africa engage in irrigation in diverse locations under different organizational modalities. This research analyses a flexible and dynamic form of irrigation driven by unique partnerships between migrants and local actors who derive benefits from land and water resources along a sand river. The case study of the ephemeral Olkeriai sand river in Kajiado, Kenya, was based on a baseline survey of 107 farm plots and 23 in-depth interviews with farmers. We found that 75% of the farm plots were managed under transient farming partnerships between migrant farmers and capital providers, locally known as tajiris, who leased land from local landowners to grow high-value market crops. These partnerships are based on flexible agreements between the actors and the frequent need to review and re-build them creates a fertile ground for new entrepreneurial players from within and outside the area, playing a key role in accelerating irrigation intensification and expansion. However, these irrigation ventures are not always successful. Unreliable partners, unstable market channels and increasing costs of irrigation inputs frequently result in farm losses and breaking up of partnership ventures. Furthermore, the lack of collective action among various resource users at the catchment level raises questions on how to sustainably manage the natural resources in sand rivers.

The Impact of Irrigation on Olive Fruit Yield and Oil Quality in a Humid Climate

The expansion of olive orchards into regions with no tradition of olive production and humid climates, such as Uruguay, with more than 1200 mm of annual rainfall, calls into question the need for irrigation. In these regions, however, years with water deficit during summers are quite common. The vapor pressure deficit during summer is lower than in countries with a Mediterranean climate. The high variability in interannual water availability in the current context of climate change, with a growing tendency for extreme events to occur, emphasizes the need to evaluate the production response of olive trees to irrigation. To achieve this, three irrigation treatments were applied to Arbequina and Frantoio cultivars according to the value of the maximum crop evapotranspiration: a first treatment applying 100% ETc, corresponding to being fully irrigated; a second treatment applying 50% ETc; and a third treatment in which neither irrigation nor rain inputs occurred from the end of the pit hardening period until harvest. Results show the possibility of an increasing fruit weight and pulp/pit ratio through irrigation in the local environmental conditions. The oil content in response to irrigation was different within cultivars. Water restriction conditions did not affect the oil content of olives in Arbequina, while in Frantoio it increased it. Polyphenols in fruit increased under water stress for both cultivars. The technological applicability of the results obtained must be accompanied by an economic analysis. The results obtained highlight the need for better use of irrigation water during the growth and ripening phase of the olive fruit under a humid climate.

Use of plastic geocellular modules as a replacement gravel layer for natural turf rootzones

AbstractA trial was conducted to assess the suitability of a novel plastic geocellular drainage layer (Permavoid) as a replacement for a conventional gravel layer in a high‐quality sports pitch. The trial was conducted during the 2014–2015 and 2015–2016 United Kingdom football (soccer) seasons. Perennial ryegrass (Lolium perenne L.) was grown under five different rootzone depth treatments (50, 100, 200, and 300 mm over Permavoid and 300 mm over gravel as a control representing current practices). These were repeated for two contrasting rootzone types. The trial area was subjected to artificial football‐style wear throughout each playing season, with irrigation and nutritional inputs as would be normal for a high‐quality football pitch. Infiltration rates, rootzone moisture content, turf cover and tractional strength for the 200‐ to 300‐mm rootzone over Permavoid and 300 mm over gravel were the same throughout the trial. The replacement of the gravel drainage layer with Permavoid had no negative effect on the rootzone's hydraulic characteristics or turfgrass growth over the 2‐yr study period. In addition, it may be possible to use shallower rootzone depths in some circumstances, reducing the volume of material needed for construction. Shallower rootzones (50–100 mm) experienced greater fluctuations in rootzone moisture content, which was likely to be directly related to rootzone depth. Rootzone type had a minor effect, with finer rootzones holding onto more moisture and allowing slightly stronger turf. Therefore, when managing shallower and/or coarser rootzones, maintenance programs need to reflect the moisture and nutrient retention characteristics of these growing media.

STAKEHOLDER INVOLVEMENT DURING PROJECT INITIATION: A SUSTAINABILITY FACTOR OF SMALLHOLDER DONOR-FUNDED IRRIGATION PROJECTS IN ZVIMBA DISTRICT, ZIMBABWE

The purpose of this study was to examine whether the involvement of stakeholders during initiation of donor-funded smallholder irrigation projects in Zvimba district, Zimbabwe, was a critical sustainability factor. Donor-funded smallholder irrigation projects investments enhance water security for agricultural production and improve peasant farmers’ livelihoods in the face of climate change induced risks. While these donor-funded smallholder irrigation investments have historically empowered local communities, ensured food security and contributed to economic growth, we have an incomplete understanding of why they collapse after the withdrawal of the donors. This paper addresses this gap by adopting the pragmatism philosophy which prompted the use of whatever works to explore how involvement of stakeholders during initiation of irrigation investments influences its sustainability. To do so, stratified and purposive sampling techniques were used to select a population of 360 people who included donor-funded irrigation project beneficiaries, community, local leaders and Agritex officers for a Zvimba district case study. The results advance that collapses of investments are consequences of non-involvement of beneficiaries in initiation of donor-funded smallholder irrigation projects. The findings highlight that in the context of irrigation projects in Zvimba district, donors, government officials and political actors were the only participants during needs assessment, stakeholder identification and project designing phases. Project beneficiaries from the communities and suppliers of irrigation equipments and inputs only came on board during the project construction phases. While findings remain contextual to the Zvimba district study area, the study concludes that non-involvement of beneficiaries, inputs suppliers, buyers, interest groups in the initiation process of the donor-funded irrigation project was a critical sustainability factor. In that context, the study recommended the adoption of a participatory donor-funded smallholder irrigation project initiation model, which calls for the involvement of all stakeholders for the entire irrigation project development life cycle.

Reduced groundwater use and increased grain production by optimized irrigation scheduling in winter wheat–summer maize double cropping system—A 16-year field study in North China Plain

Optimizing irrigation strategies to increase water utilization efficiency and achieve higher yield is vital for balancing groundwater use and improving food security during water shortage in the North China Plain (NCP). Based on a 16-year field experiment (2003–2018) using seven irrigation schedules from W0M0 to W4M3 (numbers are irrigation times in wheat (W) and maize (M) season, 75 mm each) in the winter wheat–summer maize double cropping system, we analyzed annual total water consumption ( ET a ) and groundwater table change in terms of net groundwater depletion, annual total grain yield, water productivity (WP), irrigation water productivity (IWP) and marginal benefit of the whole wheat–maize system. Relationship between yield or WP and irrigation or ET a were also revealed. Results showed that (1) total ET a increased as irrigation input increased, ranging from 427.3 mm (Rainfed, W0M0) to 891.0 mm (W4M3). Soil water storage contributed nearly 30% to ET a for winter wheat under water deficit conditions. Pre-sowing soil water storage played an important role in improving the annual yield and WP of both wheat and maize by promoting germination, seedling emergence and root growth; (2) the rainfed treatment (W0M0) was best for mitigating the groundwater table decline (0.1 m yr -1 ), followed by W1M1 (0.5 m yr -1 ) and W2M1 (0.8 m yr -1 ). Groundwater table decline in M2W2 almost overlapped the observed data at the station (1.1 m yr -1 ). In W3M2, the farmers’ traditional practice, the groundwater table declined by 1.4 m yr -1 , obviously over exploitation, while W4M2 and W4M3 declined by almost 2.0 m yr -1 ; (3) the relationship between total annual yield and irrigation (or ET a ) followed a quadratic curve. Total annual yield significantly increased from W0M0 to M1W1 (25%) to M2M1 (5%) and then kept stable. Average annual WP decreased as irrigation increased, from 2.4 kg m -3 (W0M0) to 1.6 kg m -3 (W4M3). Average annual IWP and marginal benefit also declined as irrigation increased. These results over 16 years indicated that the W2M1 is the most balanced irrigation regime for wheat– maize rotation to mitigate groundwater decline, maintain grain production, and improve water use efficiency in the NCP. ● A 16 - year field experiment of seven irrigation regimes for wheat-maize was conducted. ● ET a increased and water productivity decreased with increasing irrigation amount. ● W2M1 was the best optimized irrigation regime for balancing groundwater use and yield.

Satellite-Based Assessment of Meteorological and Agricultural Drought in Mainland Southeast Asia

Satellite-based soil moisture products allow direct monitoring of agricultural drought, especially in regions with sparse ground-based observations. In this study, a soil moisture drought index only based on satellite soil moisture is developed and adopted to assess drought in Mainland Southeast Asia. We report here on an exceptionally severe Mainland Southeast Asia drought in 2016, which is believed to be strongly linked to the 2015-2016 super El Niño strongly. The event began in February 2016 and lasted until May 2016, with more than 50% of the study areas suffering from moderate drought or worse at peak period. We assess the evolution of agricultural droughts (defined as prolonged deficit in soil moisture) by placing it in the context of the forcing meteorological drought (prolonged deficit in precipitation). The drought assessment using satellite soil moisture is temporally consistent with precipitation-based metrics, but allows for better mapping of the spatial and temporal patterns of how a precipitation deficit may or may not lead to a soil moisture deficit. The specific advantages of a remote-sensing approach—wide-coverage without need for spatially-dense, ground-based climatological records, and sensitivity to otherwise unmeasured irrigation inputs—suggest further opportunity for drought monitoring in ungauged regions, particularly in agricultural contexts.

Significance of root hairs in developing stress-resilient plants for sustainable crop production.

Root hairs represent a beneficial agronomic trait to potentially reduce fertilizer and irrigation inputs. Over the past decades, research in the plant model Arabidopsis thaliana has provided insights into root hair development, the underlying genetic frameworkand the integration of environmental cues within this framework. Recent years have seen a paradigm shift, where studies are now highlighting conservation and diversification of root hair developmental programs in other plant species and the agronomic relevance of root hairs in a wider ecological context. In this review, we specifically discuss the molecular evolution of the RSL (RHD Six-Like) pathway that controls root hair development and growth in land plants. We also discuss how root hairs contribute to plant performance as an active physiological rooting structure by performing resource acquisition, providing anchorageand constructing the rhizosphere with desirable physical, chemicaland biological properties. Finally, we outline future research directions that can help achieve the potential of root hairs in developing sustainable agroecosystems.

Effects of spatial and temporal regulation of drip emitters and tube configurations on water productivity of juvenile macadamia trees in the tropics

SummaryMacadamia in Australia is traditionally grown in semi-arid climates with hot and humid summers and cool winters supporting rainfed cultivation. Recent industry expansion into more northern, drier production areas of Queensland, Australia, requires supplementary irrigation for successful macadamia production. However, ever-increasing demand for irrigation water in these areas is both competitive and regulated. Limited information is available to optimize water use efficiency for field-grown macadamia trees. We trialled a technique that employs specially designed drip tubes with push-in emitter plugs to close emitters so that transplanting can start with emitters closed distant from tree bases and open next to the trunks of each tree. Additional emitters are then gradually opened (i.e., plugs are removed) as tree canopy size increases over subsequent years. This technique was tested on single and double in-line irrigation tube configurations per row of macadamia. Temporal regulation of emitter closure significantly reduced irrigation input by 75, 50 and 25% in the first, second and third year of treatment. Hence, irrigation over the three-year establishment period was reduced to one-half that of the non-regulated crop. These early reductions of irrigation in juvenile trees had no significant negative effects on plant growth (height, canopy spread, leaf chlorophyll and leaf photosynthetic rates), nor on nut counts. Control of emitter discharge between the plants along the row in the earlier stage (i.e., before complete within-row canopy cover) also reduced weed growth between the trees in the row. Notable growth advantages of the single in-line over the double in-line tube configuration were evident, with a non-significant but sizeable benefit on nut counts too. Effects of the temporal regulation of emitters and of in-line tube configurations must be validated on cultivars with differing water requirements and for the longer-term reproductive performance and nut quality.

Direct seeded rice in sequence with zero-tillage wheat in north-western India: addressing system-based sustainability issues

Resource conserving and eco-friendly interventions through improved crop establishment are the need of time to produce more with less resources, and mitigating climatic vulnerabilities and protecting environmental quality in the rice–wheat cropping system (RWCS) of India. In this context, seven years (2010–2017) field experimentation at Karnal, Haryana, India revealed that the weed infestation was more intensified and diversified in direct seeded rice (DSR) than puddled transplanted rice (PTR), and even eliminating puddling in rice-induced more infestation of Phalaris minor in succeeding wheat crop. Residue retention in zero-till (ZT) DSR and rotating conventional till (CT) DSR with PTR reduced weed pressure compared to continuous DSR. Root knot and plant parasitic nematodes were less in DSR than PTR but reverse was true for saprozoic nematodes in DSR and ZT situations. CTDSR, ZTDSR (with or without residues), and ZT/CT machine-transplanted rice (MTR) produced grain yields at par (P = 0.05) with PTR. The grain yield of ZT wheat (5.03–6.90 t ha−1) in sequence with CT/ZT rice establishment (DSR/MTR) was 0.3–0.6 t ha−1 higher than what it was attained after puddled rice systems. Net returns from DSR/MTR-based cropping systems were higher than PTR, with 22–31% saving of labor. Irrigation water productivity was also higher under DSR (27.5–29.9 kg ha-cm−1) than PTR (23.7 kg ha-cm−1), with 17.5–22.8% reduction in irrigation input. There was also improvement in soil health under ZTDSR/MTR (higher OC, N, P and K, and lower bulk density) compared to PTR. Overall, the resource conservation and soil health improvement through these planting methods signaled toward system stability over trade-offs in RWCS.

Effect of Mulching on Vegetable Production: A Review

Vegetables have much importance as economic, nutritional, medicinal and industrial and also have employment opportunities. However, vegetable production is a costly enterprise as it requires heavy cultural practices such as irrigation, weeding, fertilizers and protection from biotic and abiotic stress. Many times the farmers loose the entire crop in rabi and summer due to inadequate irrigation facility. In addition, seedling establishment is a tedious job in arid and semi-arid climatic conditions due to water scarcity. To improve the productivity of vegetables where either particularly non-irrigated rainfed conditions, proper moisture management of the soil is necessary. Thus, in an attempt to reducing number of irrigation and chemical inputs for weed control, mulch may be a good alternative of conventional cultivation practice. It reduces the water evaporation by interfering the radiation falling on the soil surface and thus delays the drying of the soil and reduces the soil thermal regime during the day time. It also reduces the weed population and improves the microbial activity of the soil by improving the environment around the root zone. Therefore, the practices of mulching in vegetable production have been advised to cut-down the cost of cultivation and obtain quality produce with increased profits.

Productivity Hot Spots and Cold Spots: Setting Geographic Priorities for Achieving Food Production Targets

Rice is the most important staple food in the Philippines as it provides almost half of the calorie requirements of the population. The domestic supply of rice, however, is inadequate to meet local demand, making the Philippines one of the top five rice-importing countries in the world. To close the domestic supply-and-demand gap, agricultural planners and policymakers in the Philippines have been promoting interventions to increase farm-level productivity. In support of the government efforts to increase rice productivity, a stochastic frontier analysis combined with an optimized spatial hot spot analysis was conducted to determine the factors that may influence the increase in rice farm efficiency and also identify candidate areas for relevant geographic-specific rice production interventions. Results show that enhancing access to irrigation and farm inputs and increasing the producers' technical capacity can help address the local supply deficiency by potentially increasing yield per hectare to as high as 5.50 metric tons per hectare. The approach to potentially increase rice farm technical efficiency and productivity must consider the spatial nature of rice production as suggested by the findings from the optimized hot spot analysis. It is important that policy interventions consider areas with a high incidence of low levels of productivity and technical efficiency. These are the locations where agricultural planners and policymakers can make greater impacts on rice yields. Relevant policies and initiatives, therefore, should take into account the geographical location of farms to ensure the greatest contribution to attaining food production targets.

Carbon Smart Strategies for Enhanced Food System Resilience Under a Changing Climate

There is an urgent need to match food production with increasing world population through identification of sustainable land management strategies. However, the struggle to achieve food security should be carried out keeping in mind the soil where the crops are grown and the environment in which the living things survive, especially under rainfed agricultural system. Rainfed agricultural ecosystem is extremely fragile, improving soil fertility and reducing greenhouse gas emission are key factors for developing sustainable agriculture. Moreover, society increasingly expects agriculture to be more sustainable, by decreasing irrigation and mineral fertilizer inputs. Increasing food production sustainably through efficient use of resources will strongly contribute to food security, sustainable agriculture development, and increased climate change resilience. This paper addresses the effects of carbon smart technologies on greenhouse gas emission, soil quality and crop productivity in rainfed agro ecological environment. This paper hypothesized that application of carbon smart technologies could improve soil physical and chemical properties to enhance GHG mitigation and crop production. Carbon smart technologies highlighted in this paper include minimum tillage, crop residue retention, agroforestry, biofuels, integrated nutrient management and land use management systems. This paper review and discusses the work done on carbon smart technologies in different agro-ecological regions so as to understand its impact from the perspectives of the soil, the crop and the environment. The impact of conservation agriculture on greenhouse gas emissions and the underlying mechanism in different agroecological environments have been discussed. A detailed case study and tremendous advancements on the strength of integration of trees and shrub as carbon smart technologies in improving soil and crop productivity is highlighted immensely. The paper concludes with recommendations for encouraging and improving adoption by smallholder farmers to ensure more efficient and sustainable food system. This systematic review will primarily contribute to the achievement of the following Sustainable Development Goals (SDGs), particularly SDG1 (No poverty), SDG2 (Zero hunger), SDG5 (Gender equality) and SDG13 (Climate action).

Strategic tillage achieves lower carbon footprints with higher carbon accumulation and grain yield in a wheat-maize cropping system

Continuous single tillage has the potential to increase greenhouse gas (GHG) emissions and decrease the accumulation of soil organic carbon (SOC), thus increasing carbon footprints (CFs). However, in a wheat-maize cropping system, limited information was available about the effects of strategic tillage on CFs. Thus, a four-year field experiment was conducted, including continuous rotary tillage (RT), continuous no-till (NT), RT + subsoiling (RS), and NT + subsoiling (NS), to investigate the effects of NS (strategic tillage) on the unit area and unit yield. The results showed that CO2 emission was the highest contributor to CFs (73.92%) in a winter wheat-summer maize cropping system, following the order of NS < NT < RS < RT. The direct N2O emissions from fertilizers and residues were 4.43–4.51 t CO2-eq ha−1 yr−1 during the wheat and maize seasons, and indirect N2O emissions from irrigation and fertilizer inputs had a proportion of >80% from total agricultural inputs. The differences in SOC storage significantly affected the CFs. Although the NS treatment increased the amount of GHG emissions from the residues returned and consumption of diesel, the enhancement of SOC storage by deeper SOC increased. Thus, lower area-scaled CFs were observed in the NS treatment. Furthermore, a higher grain yield and an annual change of SOC storage compared with other treatments were observed under the NS system, which helped to reduce the CFs. The yield-scaled CFs followed the order of RT > RS > NT > NS when considering the changes in SOC storage. Therefore, the NS treatment resulted in a higher grain yield and SOC sequestration with lower CFs, and thus, it could be recommended as the best tillage method to achieve sustainable production and environmental balance in a wheat-maize cropping system.

Enhancing Sustainable Potato Production—A Case Study in Northern China

Potato is the fourth most important staple crop in China. To meet the increased demand and environmental objectives, potato production should be enhanced by sustainable practices that aim to maximize yield and resource use efficiencies and minimize environmental impacts. Most experiments so far have taken place on experimental stations, while on-farm experimentation is needed to evaluate, demonstrate and scale more sustainable practices. On-farm field experiments were conducted in two years (2017, 2018) in northern China to investigate and demonstrate the effects of different nitrogen (N) fertiliser and irrigation input levels on potato yield, quality, resource use efficiency and environmental impacts. The 2017 experimental results on one farmer’s field showed that under irrigated conditions, adding N fertiliser (from 0 to 267 kg ha−1) did not increase yield due to the high soil N supply, rather it reduced tuber quality. The 2018 experimental results, in which four additional farmers were involved, indicated that, under irrigated conditions, reducing N fertiliser from the current rates (189–252 kg ha−1) to lower levels (109–181 kg ha−1) did not affect yield nor quality; while further reducing N fertiliser inputs (to 9–117 kg ha−1) resulted in a yield reduction (18% on average) in some fields. In both years, irrigation improved tuber yield and quality compared to that under rainfed conditions. The nitrogen use efficiency was improved and N surplus was reduced by applying irrigation and reducing N fertiliser input. Farmers expressed they were willing to reduce N fertiliser input by 10–20%, and indicated that a widespread adaptation of drip irrigation is hindered by the high costs and labor requirements. Site-specific recommendations on optimum N fertiliser and irrigation management must be provided, which should preferably be based on regular quantitative monitoring of soil N supply and soil moisture content.

Afforestation of Degraded Croplands as a Water-Saving Option in Irrigated Region of the Aral Sea Basin

Climate change is likely to decrease surface water availability in Central Asia, thereby necessitating land use adaptations in irrigated regions. The introduction of trees to marginally productive croplands with shallow groundwater was suggested for irrigation water-saving and improving the land’s productivity. Considering the possible trade-offs with water availability in large-scale afforestation, our study predicted the impacts on water balance components in the lower reaches of the Amudarya River to facilitate afforestation planning using the Soil and Water Assessment Tool (SWAT). The land-use scenarios used for modeling analysis considered the afforestation of 62% and 100% of marginally productive croplands under average and low irrigation water supply identified from historical land-use maps. The results indicate a dramatic decrease in the examined water balance components in all afforestation scenarios based largely on the reduced irrigation demand of trees compared to the main crops. Specifically, replacing current crops (mostly cotton) with trees on all marginal land (approximately 663 km2) in the study region with an average water availability would save 1037 mln m3 of gross irrigation input within the study region and lower the annual drainage discharge by 504 mln m3. These effects have a considerable potential to support irrigation water management and enhance drainage functions in adapting to future water supply limitations.

Interpreting Diachronic Size Variation in Prehistoric Central Asian Cereal Grains

The morphology of ancient cereal grains in Central Asia has been heavily discussed as an indicator of specific genetic variants, which are often linked to cultural factors or distinct routes of dispersal. In this paper, we present the largest currently existing database of barley (n= 631) and wheat (n= 349) measurements from Central Asia, obtained from two different periods at the Chap site (ca. 3,500 to 1,000 BC), located in the Tien Shan Mountains of Kyrgyzstan at 2,000 masl. The site is situated at the highest elevation ecocline for successful cereal cultivation and is, therefore, highly susceptible to minor climatic fluctuations that could force gradients up or down in the foothills. We contrast the Chap data with measurements from other second and first millennia BC sites in the region. An evident increase in average size over time is likely due to the evolution of larger grains or the introduction of larger variants from elsewhere. Additionally, site- or region-specific variation is noted, and we discuss potential influences for the formation of genetic varieties, including possible pleiotropic linkages and/or developmental responses to external factors, such as environmental fluctuations, climate, irrigation inputs, soil nutrients, pathologies, and seasonality. External factors acting on developmental or acclamatory responses in plants can be either natural or cultural. We argue that the study of long-term changes in grain morphology on the edges of crop-growing ranges can be informative regarding cultural and environmental constraints in the past.

Understanding soil nitrogen processes in diversified vegetable systems through agroecosystem modelling

Vegetable production systems are typically tillage- and input-intensive, though they may vary widely in production practices utilized. Improved understanding of soil water and nitrogen (N) processes with the use of agroecosystem models may aid in the optimization of crop yields and reduction of N losses. The objectives of this study were to (1) apply the RZ-SHAW model to diversified vegetable systems of varying production intensity, and (2) to elucidate soil N processes key loss pathways to inform opportunities for improving N cycling and sustainable intensification in these systems. The systems included conventional (CONV), low input organic (LI), and organic high tunnel (HT) vegetable systems. Soil water content and temperature were simulated well (rRMSE < 0.30) in all systems. Simulated soil NO3¯-N content was closer to measured values in the CONV than other systems. On average, the soil NO3¯-N content was underpredicted by 8 kg N ha−1 in the 0–0.15 m, and 5 kg N ha−1 in the 0.30–0.50 m soil layer in the LI system. In all systems, simulated daily N2O flux followed the trends in the measured values, but model predicted greater peaks than measured. Nitrate leaching was the greatest N loss pathway in all systems, though timing and driving factors varied by system. Asynchrony between N mineralization and crop uptake was observed throughout the LI rotation, indicating opportunities for targeted N and irrigation inputs to increase crop yields. Simulation results indicate the need for additional study of soil microbial and N processes in HT systems.

Exponential response of nitrous oxide (N2O) emissions to increasing nitrogen fertiliser rates in a tropical sugarcane cropping system

High rainfall, irrigation and large fertiliser nitrogen (N) inputs create conditions highly conducive for nitrous oxide (N2O) emissions in sugarcane systems. A positive non-linear response of N2O emissions to increasing N fertiliser rates has been reported from a range of cropping systems, where N inputs exceed crop requirements. However, the response of N2O emissions to N fertiliser rates in sugarcane remains largely unclear. This study monitored N2O emissions in a tropical sugarcane system in Australia to examine the response of N2O emissions to increasing N fertiliser application rates. Soil-borne N2O emissions were measured at high temporal resolution with an automated monitoring system across four N fertiliser treatments (0, 150, 200 and 250 kg N ha−1). Furrow irrigation and rainfall events triggered large N2O emissions with peak N2O emissions > 100 g N ha-1 d−1. Nitrous oxide emissions peaked when high soil nitrate (NO3-) content (> 40 kg N ha−1) coincided with water-filled pore space (WFPS) near saturation. Emissions of N2O in the first three months after N fertilisation accounted for 74–96 % of total N2O emitted over the year. Cumulative N2O emissions increased exponentially with N fertiliser rates, ranging from 0.29 to 3.06 kg N ha−1. Emission factors (EF) ranged from 0.69 to 1.11 %, exceeding the IPCC default of 1 % at 250 kg N ha−1 of N rate. The amount of N2O emitted per kg sugar yield doubled above the recommended N rate of 200 kg N ha−1. The exponential response of N2O to fertiliser N suggests that N2O emissions from intensive sugarcane systems with high fertiliser N inputs are considerably larger than currently assumed and that a non-linear model may be more appropriate for estimating N2O emissions from sugarcane soils. The steep increase in N2O intensity demonstrates environmental inefficiency at high fertiliser N rates, emphasising the importance of avoiding excessive N fertiliser application in tropical sugarcane systems from both agronomic and environmental perspectives.

Effect of Organic and Conventional Production Methods on Fruit Yield and Nutritional Quality Parameters in Three Traditional Cretan Grape Varieties: Results from a Farm Survey.

The antioxidants found in grapes and wine have been linked to health benefits in humans, but may be affected by agronomic parameters, grape type/variety, and processing. Here, we report results of a farm survey which investigated the effects of production system (organic vs. conventional) and grape variety on fruit yield, total antioxidant activity/capacity (TAA, assessed by the Trolox Equivalent Antioxidant Capacity (TEAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays), and total concentrations of total phenolics (TPC) and anthocyanins (TAC) in grapes of one red (Kotsifali) and two white (Villana and/or Vidiano) traditional Cretan grape varieties. Analysis of variance (ANOVA) results showed that grape variety choice had a more substantial effect on TPC, TAA, and TAC than primary production protocols, and significant interactions were identified between production system and grape variety choice for TAATEAC. Specifically, TAATEAC was significantly (57%) higher in organic than conventional Vidiano grapes, while there was no significant effect of production system on TAATEAC in Kotsifali and Villana grapes. As expected from previous studies, the TAC was substantially higher in red Kotsifali grapes. Redundancy analysis (RDA) identified grape variety as the only strong explanatory variable/driver for yield, TPC, TAA, and TAC of table grapes, and positive associations were detected between the variety Vidiano and both TPC and TAATEAC. All other explanatory variables included in the RDA (including supplementary irrigation, orchard orientation, production system, soil type, vineyard age, plant density, and fertiliser inputs) explained only a small proportion of the additional variation.

Forage Yield and Quality of Winter Canola–Pea Mixed Cropping System

Forage crop–dairy farming is an important agro-industry across the world. This system is intensive with high-input forage crops. In the United States (US) Southern Great Plains, the system is based primarily on high-input annual grass-type crops in monocropping approaches and requires diverse low-input broadleaf crops for strengthening its sustainability. Winter canola (Brassica napus L.) and pea (Pisum sativum L.) have the potential to provide forage crop diversity options with high forage yields of high quality. Winter canola and pea in mono- and mixed-cropping approaches at seeding ratios of canola/pea at 0:100, 25:75, 50:50, 75:25, and 100:0 were studied for yield and quality in 2015 and 2016 in Clovis, New Mexico (NM). Averaged over years, canola–pea at 75:25 and 50:50 seeding ratios produced similar biomass forage yield but higher than mono-pea by 43% and canola–pea at 25:75 and mono-canola cropping by 8%. The land equivalent ratio of all mixed-cropping treatments exceeded 1.0, with canola–pea at the 50:50 seeding ratio recording a land equivalent ratio of 1.15, indicating that mixed-cropping systems are better users of land resources. Total digestible nutrients and relative feed value were higher in canola–pea mixed cropping than in mono-canola and mono-pea cropping. Canola–pea mixed cropping achieved high yields (13.3 to 14.7 Mg·ha−1) with improved forage quality, as well as improved crop and land productivity, with the potential to improve mechanical harvestability of vining pea, and strengthen the diversity and sustainability of forage crop–dairy farming in the Southern Great Plains under limited irrigation input of ~300 mm.