The role of soil characteristics,soil tillage and drip irrigation in the timber production of a wild cherry orchard under Mediterranean conditions

Over the last decade high-quality timber plantations have increased in Europe because of the constant high market price of timber and economical incentives from the EU. These latter are mainly due to timber plantations’ role in CO₂ capture. Noble wood plantations have also been established in Mediterranean areas, but many of them suffer from low growth rates due to deficient plantation management and/or non-optimal environmental conditions. Furthermore, little information exists about soil and water management in these plantations and how different soil characteristics may affect management results. In this study, a trial was established in a pure wild cherry plantation under Mediterranean conditions. The trial evaluated the effects that soil type (low soil quality versus good performance for woody crops), soil management (soil tillage versus no tillage), irrigation regime (drip irrigation versus no irrigation) and their interactions may have on wood production. Soil water content and the spontaneous vegetation that appeared in the alleys of the no-tillage treatments were also measured.The results showed that sandy-clay-loam soil with a water-holding capacity of 101.5 ± 5.2 mm had 65% more wood volume increase during the study period than sandy-loam soil with a water-holding capacity of 37.9 ± 8.0 mm. Conventional tillage or zero tillage with the presence of spontaneous vegetation did not differ significantly in wood volume increment, regardless of the type of soil. Although soil water content was significantly increased by tillage in sandy-loam soil, this effect was not enough to increase tree wood volume. On the other hand, the application of drip irrigation did increase wood production by up to 50%. Therefore, 10 years less on the plantation's rotation length can be anticipated when applying irrigation: from 40 to 30 years (sandy–clay–loam soil) and from 56 to 46 years (sandy-loam soil).In conclusion, deep soil characterization of the site is essential before deciding whether to develop a plantation of this type in areas under soil water content limitations caused by deficient soil structure and texture. In addition, our results show important savings can be made by reducing soil tillage, as less tillage leads to greater ground cover and biodiversity. Further investigations are required to examine how long-lasting the effects are and what other benefits can be expected when this type of plantation is managed in a more sustainable way.     

Maize yield and water balance is affected by nitrogen application in a film-mulching ridge–furrow system in a semiarid region of China

Poor soil and drought stress are common in semiarid areas of China, but maize has a high demand for nitrogen (N) and water. Maize production using the technique of double ridges and furrows mulched with plastic film are being rapidly adopted due to significant increases in yield and water use efficiency (WUE) in these areas. This paper studied N use and water balance of maize crops under double ridges and furrows mulched with plastic-film systems in a semiarid environment over four growing seasons from 2007 to 2010. To improve precipitation storage in the non-growing season, the whole-year plastic-film mulching technique was used. There were six treatments which had 0, 70, 140, 280, 420 or 560 kg N ha⁻¹ applied in every year for maize. In April 2011, spring wheat was planted in flat plots without fertilizer or mulch following four years of maize cultivation. After four years, all treatments not only maintained soil water balance in the 0–200 cm soil layer but soil water content also increased in the 0–160 cm soil layer compared to values before maize sowing in April 2007. However, under similar precipitation and only one season of spring wheat, soil water content in the 0–160 cm soil layer sharply decreased in all treatments compared to values before sowing in April 2011. Over the four years of maize cultivation, average yield in all treatments ranged from 4071 to 6676 kg ha⁻¹ and WUE ranged from 18.2 to 28.2 kg ha⁻¹ mm⁻¹. In 2011, the yield of spring wheat in all treatments ranged from 763 to 1260 kg ha⁻¹ and WUE from 3.5 to 6.5 kg ha⁻¹ mm⁻¹. The potential maximum grain yield for maize was 6784 kg ha⁻¹ with 360 kg N ha⁻¹ applied for four years, but considerable NO₃N accumulated in the soil profile. A lesser application (110 kg N ha⁻¹) to this tillage system yielded in 82% of the maximum, increased nitrogen use efficiency and mitigated the risk of nitrogen loss from the system. This study suggests that double ridge–furrow and whole-year plastic-film mulching could sustain high grain yields in maize with approximately 110 kg N ha⁻¹ and maintain soil water balance when annual precipitation is >273 mm in this semiarid environment.     

Impact of tillage and mulch management on economics,energy requirement and crop performance in maize–wheat rotation in rainfed subhumid inceptisols,India

Different tillage systems (conventional, minimum, raised bed and no tillage) and four mulch levels (control, polythene, straw and soil) were compared in maize (Zea mays) and wheat (Triticum aestivum) production for three years on an experimental field (sandy loam) located at Dry Land Research Sub Station, Dhiansar, Jammu. Each treatment was replicated four times in split plot design. The aim of the research was to determine the influence of tillage and mulch practices on economics, energy requirement, soil physical properties and performance of maize and wheat. Tillage methods significantly affected the soil physical properties as change in soil moisture contents and infiltration rate of soil was recorded. The soil moisture contents in minimum tillage (MT) were maximum (12.4%, 16.6%) in surface soil as compared to conventional tillage (CT) in maize and wheat crops, respectively. Comparing to the CT infiltration rate was (1.16times, 1.21times and 1.11times) higher in minimum tillage (MT), no tillage (NT) and raised bed (RB), respectively in kharif season. Similar results were also found in rabi season. The greatest maize yield of 1865 kg ha^?1 was achieved with CT system while not significantly lower yield was achieved with MT system (1837 kg ha^?1). However, wheat yield was recorded higher in MT as compare to the CT system. Comparing to the energy requirement of different operations, MT required 34.3% less, NT 31.1% less and RB 46.0% less than the CT system. MT system saved 2.5 times energy in tillage operation compared to the CT system. The economic analysis also revealed that the maximum benefits could be obtained from MT (EUR 202.4 ha^?1) followed by RB (EUR 164.2 ha^?1) and NT (EUR 158.3 ha^?1) and lowest in CT (EUR 149.5 ha^?1). Benefit-cost ratio was highest in MT (0.71) and lowest in CT (0.44). Results revealed that mulch significantly affected the soil physical properties and growth of maize. The maximum soil moisture content, infiltration rate and grain yield of maize and wheat recorded higher in mulching practices over no mulch treatment. Polythene mulch and straw mulch were almost equally valuable in maize and wheat sequence. Tillage (minimum) and mulch (polythene and straw) have pronounced effect on soil physical properties (improved infiltration rate and conserve soil water), energy requirement, economics and growth of maize and wheat.     

Short and long-term effects of different irrigation and tillage systems on soil properties and rice productivity under Mediterranean conditions

In Mediterranean environments, flood irrigation of rice (Oryza sativa L.) crops is in danger of disappearance due to its unsustainable nature. The aim of the present study was to determine the short- and long-term effects of aerobic rice production, combined with conventional and no-tillage practices, on soils' physical, physicochemical, and biological properties, as well as on the rice yield components and productivity in the semi-arid Mediterranean conditions of SW Spain. A field experiment was conducted for three consecutive years (2011, 2012, and 2013), with four treatments: anaerobic with conventional tillage and flooding (CTF), aerobic with conventional tillage and sprinkler irrigation (CTS), aerobic with no-tillage and sprinkler irrigation (NTS), and long-term aerobic with no-tillage and sprinkler irrigation (NTS7). Significant soil properties improvements were achieved after the long-term implementation of no-tillage and sprinkler irrigation (NTS7). The short-term no-tillage and sprinkler irrigated treatment (NTS) gave lower yields than CTF in 2011 and 2012, but reached similar yields in the third year (NTS 8229 kg ha⁻¹; CTF 8926 kg ha⁻¹), with average savings of 75% of the total amount of water applied in CTF. The NTS7 data showed that high yields (reaching 9805 kg ha⁻¹ in 2012) and water savings are sustainable in the long term. The highest water productivity was with NTS7 in 2011 (0.66 g L⁻¹) and 2012 (1.46 g L⁻¹), and with NTS in 2013 (1.05 g L⁻¹). Thus, mid- and long-term implementation of sprinkler irrigation combined with no-tillage may be considered as a potentially productive and sustainable rice cropping system under Mediterranean conditions.     

Use of soil and vegetation spectroradiometry to investigate crop water use efficiency of a drip irrigated tomato

An agronomic research was conducted in Tuscany (Central Italy) to evaluate the effects of an advanced irrigation system on the water use efficiency (WUE) of a tomato crop and to investigate the ability of soil and vegetation spectroradiometry to detect and map WUE. Irrigation was applied following an innovative approach based on CropSense system. Soil water content was monitored at four soil depths (10, 20, 30 and 50 cm) by a probe. Rainfall during the crop cycle reached 162 mm and irrigation water applied with a drip system amounted to 207 mm, distributed with 16 irrigation events. Tomato yield varied from 7.10 to 14.4 kg m⁻², with a WUE ranging from 19.1 to 38.9 kg m⁻³. The irrigation system allowed a high yield levels and a low depth of water applied, as compared to seasonal ET crop estimated with Hargraves’ formula and with the literature data on irrigated tomato. Measurements were carried out on geo-referenced points to gather information on crop (crop yield, eighteen Vegetation indices, leaf area index) and on soil (spectroradiometric and traditional analysis). Eight VIs, out of nineteen ones analyzed, showed a significant relationship with georeferenced yield data; PVI maps seemed able to return the best response, before harvesting, to improve the knowledge of the area of cultivation and irrigation system. CropSense irrigation system reduced seasonal irrigation volumes. Some vegetation indexes were significantly correlated to tomato yield and well identify, a posteriori, crop area with low WUE; spectroradiometry can be a valuable tool to improve irrigated tomato field management.     

Yield decrease in sugar beet caused by reduced tillage and direct drilling

In a long-term series of on-farm tillage trials (10 loessial sites in southern and eastern Germany; annual mouldboard ploughing 0.25–0.3 m deep, mulching with a rigid-tine cultivator 0.1–0.15 m deep, direct drilling with no tillage except seedbed preparation for sugar beet solely) sugar beet yield was significantly decreased by direct drilling compared to ploughing. This study was conducted to (i) show that the lower plant density caused by mulching and direct drilling contributes to yield decrease but explains effects just partially, and (ii) determine the relation between soil structural properties and sugar beet yield. In 2003–2005 plant density experiments (53,000, 65,000 and 82,000 plants ha^?1) were introduced to tillage plots on five selected environments. Yield and soil structural properties of four layers representing 0–0.43 m soil depth were determined.White sugar yield (WSY) significantly declined with direct drilling compared to ploughing treatment, whereas mulching treatment diminished WSY less pronounced. Moreover, decreasing plant density significantly lowered WSY. No interactions between tillage and plant density occurred, revealing that both factors additively affected WSY.Decreasing tillage depth increased penetration resistance (PR) and dry bulk density (DBD), and diminished air filled pore volume (AFPV) in the topsoil down to 0.27 m depth. Several soil structural parameters were closely correlated with each other as well as WSY. Variation of single parameters explained up to 60% of WSY variance attributed to tillage. Combining DBD from 0.03 to 0.07 m depth, average PR from 0.03 to 0.27 m and AFPV from 0.03 to 0.18 m soil depth explained 77% of the tillage effect. Nevertheless, multi-collinearity of soil physical parameters allowed no clear conclusions on the cause-and-effect mechanisms.Conclusively, lowered plant density and soil structure degradation due to reduced tillage may independently decrease sugar beet yield. When grown on loessial soils this crop requires mechanical loosening down to 0.15–0.20 m depth to produce high yields.     

Spatial distribution of soil water,soil temperature,and plant roots in a drip-irrigated intercropping field with plastic mulch

Intercropping and drip irrigation with plastic mulch are two agricultural practices used worldwide. Coupling of these two practices may further increase crop yields and land and water use efficiencies when an optimal spatial distribution of soil water contents (SWC), soil temperatures, and plant roots is achieved. However, this coupling causes the distribution of SWCs, soil temperatures, and plant roots to be more complex than when only one of these agricultural practices are used. The objective of this study thus was to investigate the effects of different irrigation treatments on spatial distributions of SWCs, soil temperatures, and root growth in a drip-irrigated intercropping field with plastic mulch. Three field experiments with different irrigation treatments (high T1, moderate T2, and low T3) were conducted to evaluate the spatial distribution of SWCs, soil temperatures, and plant roots with respect to dripper lines and plant locations. There were significant differences (p < 0.05) in SWCs in the 0–40 cm soil layer for different irrigation treatments and between different locations. The maximum SWC was measured under the plant/mulch for the T1 treatment, while the minimum SWC was measured under the bare soil surface for the T3 treatment. This was mainly due to the location of drippers and mulch. However, no differences in SWCs were measured in the 60 100 cm soil layer. Significant differences in soil temperatures were measured in the 0 5 cm soil layer between different irrigation treatments and different locations. The soil temperature in the subsoil (15 25 cm) under mulch was higher than under the bare surface. The overlaps of two plant root systems in an intercropping field gradually increased and then decreased during the growing season. The roots in the 0 30 cm soil layer accounted for about 60% 70% of all roots. Higher irrigation rates produced higher root length and weight densities in the 0 30 cm soil layer and lower densities in the 30 100 cm soil layers. Spatial distributions of SWCs, soil temperatures, and plant roots in the intercropping field under drip irrigation were significantly influenced by irrigation treatments and plastic mulch. Collected experimental data may contribute to designing an optimal irrigation program for a drip-irrigated intercropping field with plastic mulch.     

Response of giant reed (Arundo donax L.) to nitrogen fertilization and soil water availability in semi-arid Mediterranean environment

The aim of the present work was to evaluate the effect of soil water availability and nitrogen fertilization on yield, water use efficiency and agronomic nitrogen use efficiency of giant reed (Arundo donax L.) over four-year field experiment.After the year of establishment, three levels for each factor were studied in the following three years: I₀ (irrigation only during the year of establishment), I₁ (50% ETm restitution) and I₂ (100% ETm restitution); N₀ (0 kg N ha⁻¹), N₁ (60 kg N ha⁻¹) and N₂ (120 kg N ha⁻¹).Irrigation and nitrogen effects resulted significant for stem height and leaf area index (LAI) before senescence, while no differences were observed for stem density and LAI at harvest.Aboveground biomass dry matter (DM) yield increased following the year of establishment in all irrigation and N fertilization treatments. It was always the highest in I₂N₂ (18.3, 28.8 and 28.9 t DM ha⁻¹ at second, third and fourth year growing season, respectively). The lowest values were observed in I₀N₀ (11.0, 13.4 and 12.9 t DM ha⁻¹, respectively).Water use efficiency (WUE) was significantly higher in the most stressed irrigation treatment (I₀), decreasing in the intermediate (I₁) and further in the highest irrigation treatment (I₂). N fertilization lead to greater values of WUE in all irrigation treatment.The effect of N fertilization on agronomic nitrogen use efficiency (NUE) was significant only at the first and second growing season.Giant reed was able to uptake water at 160–180 cm soil depth when irrigation was applied, while up to 140–160 cm under water stress condition.Giant reed appeared to be particularly suited to semi-arid Mediterranean environments, showing high yields even in absence of agro-input supply.     

Ridge-furrow mulching system in semiarid Kenya: A promising solution to improve soil water availability and maize productivity

In semiarid Kenya, field productivity of maize has been at a low integrity level due to insufficient use of rainwater use. From 2012 to 2013, an innovative ridge-furrow mulching system (RFMs) was tested using local maize (Zea mays L.) hybrid, KCB in KARI-Katumani Farm, Kenya in long and short rainy seasons. Field experiments were conducted in a randomized complete block design with four treatments: 1) RFMs with transparent polyethylene film (RFT), 2) RFMs with black polyethylene film (RFB), 3) RFMs with grass straw mulching (RFS), and 4) RFMs without mulching (CK). Soil moisture & temperature, grain yield, water use and economic benefit were determined and analyzed. The results indicated that both RFT and RFB treatments significantly increased soil water storage amount in the depth of 0–60 cm. Grain yield and water use efficiency (WUE) in both treatments were increased by 66.5–349.9% and 72.9–382% respectively, compared with those of CK over two growing seasons. In addition, grain yield and WUE in RFS treatment were only increased by from 4.2–127.1% compared with those of CK. Particularly, two types of plastic films displayed different effects on modifying topsoil temperature. Transparent film mulching significantly increased topsoil temperature by 1.3 °C (p < 0.05) higher than CK, to facilitate growth and grain formation in long (but cool) growing season. In contrast, black film mulching lowered soil temperature by 0.3 °C lower than CK in short (but warm) growing season, which led to better soil thermal balance. Overall, RFMs with film mulching could serve as an effective solution to increase maize productivity, and hence a promising strategy to cope with food security under climate change in semiarid Kenya.     

Stable isotope technique in the evaluation of tillage and fertilizer effects on soil carbon and nitrogen sequestration and water use efficiency

Agricultural soil could be made to serve as a sink rather than a source of greenhouse gases by suitable soil management. This study was, therefore, conducted to assess the impact of tillage and fertilizer application on soil and plant carbon and nitrogen fractionation and intrinsic water use efficiency (iWUE). The experiment was a split–split-plot factorial design with three replications. The main plot consisted of two tillage treatments: zero tillage (ZT) and conventional tillage (CT). The sub-plot contained four NPK fertilizer treatments (0, 90, 120 and 150 kg N ha⁻¹), while the sub–sub-plot comprised three poultry manure (PM) treatments (0, 10 and 20 Mg ha⁻¹). Soil carbon and nitrogen sequestration were evaluated using stable isotope of carbon (δ¹³C) and nitrogen (δ¹⁵N). The δ¹³C in maize plant was used to obtain iWUE. It was observed that soil δ¹³C and δ¹⁵N were more depleted under ZT than CT and in plots treated with 20 Mg ha⁻¹ PM (PM₂₀) implying carbon and nitrogen sequestration under ZT and by PM₂₀. Relative to the control, application of PM₂₀ raised soil δ¹⁵N enrichment by 82% and 96% under CT and ZT, respectively. Higher iWUE of 25.7% was obtained under CT and was significantly higher than the iWUE values under ZT in the second year of the study while the iWUE was significantly lower with PM₂₀ application than other fertilizer treatments. The significant δ¹³C depletion and hence lower iWUE with combination of NPK fertilizer and PM under CT than the control implied that soil disturbance under tilled plots was mediated by combined nutrient management thereby limiting soil C available for fractionation resulting in lower iWUE. This suggests that conservation tillage such as zero tillage and integrated application of organic and inorganic fertilizers are good strategies for reducing soil carbon and nitrogen emission.     

Tillage,cover crops,and nitrogen fertilization effects on soil nitrogen and cotton and sorghum yields

Sustainable soil and crop management practices that reduce soil erosion and nitrogen (N) leaching, conserve soil organic matter, and optimize cotton and sorghum yields still remain a challenge. We examined the influence of three tillage practices (no-till, strip till and chisel till), four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secaele cereale L.)], vetch/rye biculture and winter weeds or no cover crop}, and three N fertilization rates (0, 60–65 and 120–130 kg N ha⁻¹) on soil inorganic N content at the 0–30 cm depth and yields and N uptake of cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench]. A field experiment was conducted on Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) from 1999 to 2002 in Georgia, USA. Nitrogen supplied by cover crops was greater with vetch and vetch/rye biculture than with rye and weeds. Soil inorganic N at the 0–10 and 10–30 cm depths increased with increasing N rate and were greater with vetch than with rye and weeds in April 2000 and 2002. Inorganic N at 0–10 cm was also greater with vetch than with rye in no-till, greater with vetch/rye than with rye and weeds in strip till, and greater with vetch than with rye and weeds in chisel till. In 2000, cotton lint yield and N uptake were greater in no-till with rye or 60 kg N ha⁻¹ than in other treatments, but biomass (stems + leaves) yield and N uptake were greater with vetch and vetch/rye than with rye or weeds, and greater with 60 and 120 than with 0 kg N ha⁻¹. In 2001, sorghum grain yield, biomass yield, and N uptake were greater in strip till and chisel till than in no-till, and greater in vetch and vetch/rye with or without N than in rye and weeds with 0 or 65 kg N ha⁻¹. In 2002, cotton lint yield and N uptake were greater in chisel till, rye and weeds with 0 or 60 kg N ha⁻¹ than in other treatments, but biomass N uptake was greater in vetch/rye with 60 kg N ha⁻¹ than in rye and weeds with 0 or 60 kg N ha⁻¹. Increased N supplied by hairy vetch or 120–130 kg N ha⁻¹ increased soil N availability, sorghum grain yield, cotton and sorghum biomass yields, and N uptake but decreased cotton lint yield and lint N uptake compared with rye, weeds or 0 kg N ha⁻¹. Cotton and sorghum yields and N uptake can be optimized and potentials for soil erosion and N leaching can be reduced by using conservation tillage, such as no-till or strip till, with vetch/rye biculture cover crop and 60–65 kg N ha⁻¹. The results can be applied in regions where cover crops can be grown in the winter to reduce soil erosion and N leaching and where tillage intensity and N fertilization rates can be minimized to reduce the costs of energy requirement for tillage and N fertilization while optimizing crop production.     

Organic amendment and minimum tillage in winter wheat grown in Mediterranean conditions: Effects on yield performance,soil fertility and environmental impact

The experiment was conducted to evaluate the agronomic benefit of the application of organic fertilizers combined with different soil tillage on quantitative and qualitative components of winter wheat (Triticum durum Desf., cv. ‘Simeto’) and on chemical soil fertility parameters. The environmental impact, due to heavy metals introduced in soil-plant system, was further investigated. Soil tillage treatments consisted of conventional (CT) and minimum tillage (MT). Fertilization treatments were: mineral at 100 kg N ha⁻¹ (N_min); municipal solid waste compost at 100 kg N ha⁻¹ (N_comp); 50 kg N ha⁻¹ of both compost and mineral fertilizers (N_mix); sewage sludge at 100 kg N ha⁻¹ (N_ss). These treatments were compared with an unfertilized control (N₀). No significant difference was observed between the two soil tillage treatments for quantitative yield production, while among the fertilization treatments N_ss did not show any significant difference compared to N_min. At the end of the research, the fertility of the soil (oxidable carbon, total nitrogen, available phosphorus) was on average higher in N_comp and N_ss treatments compared to the N₀ and N_min ones. The overall distribution of heavy metals in soil-plant system respect to the different fertilizer treatments has not allowed to grouped their effects with Principal Components Analysis. This result showed that the amount of potential pollutants applied by organic amendments did not modified the dynamic equilibrium of the soil–plant system. The MT, as well as the fertilization with the application of sewage sludge (N_ss), allowed to reach productive performance similar to conventional management (CT with N_min). Here we demonstrate that, in the short term period, sustainable agronomical techniques can replace the conventional one with environmental benefit.     

Long term effects of tillage practices and N fertilization in rainfed Mediterranean cropping systems: durum wheat,sunflower and maize grain yield

Long term investigations on the combined effects of tillage systems and other agronomic practices such as mineral N fertilization under Mediterranean conditions on durum wheat are very scanty and findings are often contradictory. Moreover, no studies are available on the long term effect of the adoption of conservation tillage on grain yield of maize and sunflower grown in rotation with durum wheat under rainfed Mediterranean conditions. This paper reports the results of a 20-years experiment on a durum wheat-sunflower (7 years) and durum wheat–maize (13 years) two-year rotation, whose main objective was to quantify the long term effects of different tillage practices (CT = conventional tillage; MT = minimum tillage; NT = no tillage) combined with different nitrogen fertilizer rates (N0, N1, N2 corresponding to 0, 45 and 90 kg N ha⁻¹ for sunflower, and 0, 90 and 180 kg N ha⁻¹ for wheat and maize) on grain yield, yield components and yield stability for the three crops. In addition, the influence of meteorological factors on the interannual variability of studied variables was also assessed. For durum wheat, NT did not allow substantial yield benefits leading to comparable yields with respect to CT in ten out of twenty years. For both sunflower and maize, NT under rainfed conditions was not a viable options, because of the unsuitable (i.e., too wet) soil conditions of the clayish soil at sowing. Both spring crops performed well with MT. No significant N × tillage interaction was found for the three crops. As expected, the response of durum wheat and maize grain yield to N was remarkable, while sunflower grain yield was not significantly influenced by N rate. Wheat yield was constrained by high temperatures in January during tillering and drought in April during heading. The interannual yield variability of sunflower was mainly associated to soil water deficit at flowering and air temperature during seed filling. Heavy rains during this latter phase strongly constrained sunflower grain yield. Maize grain yield was negatively affected by high temperatures in June and drought in July, this latter factor was particularly important in the fertilized maize. Considering both yield and yield stability, durum wheat and sunflower performed better under MT and N1 while maize performed better under both CT and MT and with N2 rates. The results of this long term study are suitable for supporting policies on sustainable Mediterranean rainfed cropping systems and also for cropping system modelling.     

Mineral nitrogen dynamics in irrigated rice–wheat system under different irrigation and establishment methods and residue levels in arid drylands of Central Asia

Increasing water shortage and low water productivity in the irrigated drylands of Central Asia are compelling farmers to develop and adopt resource conservation technologies. Nitrogen (N) is the key nutrient for crop production in rice–wheat cropping systems in this region. Nitrogen dynamics of dry seeded rice-(aerobic, anaerobic) planted in rotation with wheat (well drained, aerobic) can differ greatly from those of conventional rice cultivation. Soil mineral N dynamics in flood irrigated rice has extensively been studied and understood, however, the impact of establishment method and residue levels on this dynamics remains unknown. Experiments on resource conservation technologies were conducted between 2008 and 2009 to assess the impact of two establishment methods (beds and flats) in combination with three (R0, R50 and R100) residue levels and two irrigation modes (alternate wet and dry (AWD) irrigation (all zero till), and a continuously flooded conventional tillage (dry tillage)) with water seeded rice (WSR) on the mineral N dynamics under dry seeded rice (DSR)-surface seeded wheat systems. N balance from the top 80 cm soil layers indicated that 32–70% (122–236 kg ha⁻¹) mineral N was unaccounted (lost) during rice cropping. The amount of unaccounted mineral N was affected by the irrigation method. Residue retention increased (p < 0.001) the unaccounted mineral N content by 38%. With AWD irrigation, the N loss was not different among dry seeded rice in flat (DSRF), dry seeded rice in bed (DSRB), and conventional tillage WSR. Under different irrigation, establishment methods and residue levels, unaccounted mineral N was mainly affected by plant N uptake and soil mineral N content. Major amounts (43–58%) of unaccounted mineral N from DSR field occurred between seeding and panicle initiation (PI). During the entire rice and wheat growing seasons, NH₄N consistently remained at very high levels, while, NO₃N remained at very low levels in all treatments. In rice, the irrigation method affected NH₄N content. Effect of residue retention and establishment methods were not significant on NH₄N and NO₃N dynamics in both crops and years. Further evidence of the continuously fluctuating water filled pore spaces (WFPS) of 64% and the microbial aerobic activity of 93% at the top 10 cm soil surface during rice growing season indicates soil in the DSR treatments was under frequent aerobic–anaerobic transformation, a conditions very conducive for higher amounts of N loss. In DSR treatments, the losses appeared to be caused by a combination of denitrification, leaching and N immobilization. When intending to use a DSR management strategies need to be developed for appropriate N management, irrigation scheduling, and residue use to increase mineral N availability and uptake before this practices can be recommended.     

Impacts of conservation agriculture on total soil organic carbon retention potential under an irrigated agro-ecosystem of the western Indo-Gangetic Plains

Sequestration of C in arable soils has been considered as a potential mechanism to mitigate the elevated levels of atmospheric greenhouse gases. We evaluated impacts of conservation agriculture on change in total soil organic C (SOC) and relationship between C addition and storage in a sandy loam soil of the Indo-Gangetic Plains. Cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) crops were grown during the first three years (2008–2011) and in the last year, maize (Zea mays L.), wheat and green gram (Vigna radiate L.) were cultivated. Results indicate the plots under zero tillage with bed planting (ZT-B) and zero tillage with flat planting (ZT-F) had nearly 28 and 26% higher total SOC stock compared with conventional tillage and bed planting (CT-B) (∼5.5 Mg ha⁻¹) in the 0–5 cm soil layer. Plots under ZT-B and ZT-F contained higher total SOC stocks in the 0–5 and 5–15 cm soil layers than CT-B plots. Although there were significant variations in total SOC stocks in the surface layers, SOC stocks were similar under all treatments in the 0–30 cm soil layer. Residue management had no impact on SOC stocks in all layers, despite plots under cotton/maize + wheat residue (C/M+ W RES) contained ∼13% higher total SOC concentration than no residue treated plots (N RES; ∼7.6 g kg⁻¹) in the 0–5 cm layer. Hence, tillage and residue management interaction effects were not significant. Although CT-B and ZT-F had similar maize aboveground biomass yields, CT-F treated plots yielded 16% less maize biomass than CT-B plots. However, both wheat and green gram (2012) yields were not affected by tillage. Plots under C/M + W RES had ∼17, 13, 13 and 32% higher mean cotton, maize, wheat and green gram aboveground biomass yields than N RES plots, yielding ∼16% higher estimated root (and rhizodeposition) C input in the 0–30 cm soil layer than N RES plots. About 9.3% of the gross C input contributed towards the increase in SOC content under the residue treated plots. However, ∼7.6 and 10.2% of the gross C input contributed towards the increase in SOC content under CT and ZT, respectively. Thus, both ZT and partial or full residue retention is recommended for higher soil C retention and sustained crop productivity.     

Yield,water use and radiation use efficiencies of kenaf (Hibiscus cannabinus L.) under reduced water and nitrogen soil availability in a semi-arid Mediterranean area

Kenaf is a warm-season species that recently has been proved to be a good source of biomass for cellulose pulp for the paper industry in Mediterranean countries, where the use of hemp is problematic for legal reasons. A two-year research program aiming at studying the effects of different water regimes and nitrogen fertilization levels, upon plant growth, leaf area index, biomass accumulation, water and radiation use efficiency, was carried out on kenaf under a typically semi-arid Mediterranean climate of South Italy. In cv. Tainung 2, four different water regimes (I₀ = no irrigation, I₂₅, I₅₀ and I₁₀₀ = 25, 50 and 100% ETc restoration, respectively) and three nitrogen levels (N₀ = no nitrogen, N₇₅ and N₁₅₀ = 75 and 150 kg ha⁻¹ of N, respectively) were studied. The amount of water applied strongly affected plant growth (in terms of LAI, plant height and biomass) and final total and stem dry yield, which significantly increased from I₀ to I₁₀₀. Nitrogen did not exert any beneficial effect upon dry yield. Radiation Use Efficiency (RUE), calculated in the second year only, was the highest (1.95 g DM MJ⁻¹) in fully irrigated treatment (I₁₀₀) and the lowest (0.86 g DM MJ⁻¹) in the dry control.Water use efficiency (WUE) was rather similar among water regimes, whilst irrigation water use efficiency (IWUE) progressively increased with the decrease of total volume of water distributed to the crop by irrigation, from 3.47 to 12.45 kg m⁻³ in 2004 and from 4.27 to 7.72 kg m⁻³ in 2005. The results obtained from this research demonstrate that in semi-arid areas of South Italy, irrigation at a reduced rate (50% ETc restoration) may be advantageous, since it allowed a 42–45% irrigation water saving, when compared to the fully irrigation treatment, against a 23% (in 2004) and 36% (in 2005) yield reduction, and a still good efficiency (near that potential) in transforming the solar radiation in dry biomass was maintained (RUE = 1.76 g DM MJ⁻¹, against 1.95 g DM MJ⁻¹ in fully irrigated treatment).     

Fourteen years of applying zero and conventional tillage,crop rotation and residue management systems and its effect on physical and chemical soil quality

Soil management systems may negatively affect the quality of the soil. Policymakers and farmers need scientific information to make appropriate land management decisions. Conventional (CT) and zero tillage (ZT) are two common soil management systems. Comparative field studies under controlled conditions are required to determine the impact of these systems on soil quality and yields. The research presented studied plant and soil physical and chemical characteristics as affected by different agricultural management practices, i.e. ZT and CT, cropped with continuous wheat or maize in monoculture (M) or in a yearly rotation (R) of these two crops, either with residue retention (+r) or without residues retention (?r), in an experimental field in the Transvolcanic Belt of Mexico after 14 years. The dominant factors defining soil quality were organic C, total N, moisture, aggregate stability, mechanical resistance, pH and EC. The principal component combining the variables organic C, total N, aggregate stability and moisture content showed the highest correlations with final yield (R = 0.85 for wheat and 0.87 for maize).After 14 years of continuous practice, ZTM + r and ZTR + r had the best soil quality and produced the highest wheat and maize yields of average 2001–2004 (6683 and 7672 kg ha^?1 and 5085 and 5667 kg ha^?1, respectively). Removing the residues, i.e. treatments ZTM ? r with maize (average 2001–2004: 1388 kg ha^?1) and ZTR ? r and CTR ? r with wheat (average 2001–2004: 3949 and 5121 kg ha^?1), gave the lowest yields and less favourable soil physical and chemical characteristics compared to the other practices. It was found that zero tillage with residue retention is a feasible management technology for farmers producing maize and wheat in the agro-ecological zone studied, resulting in a better soil quality and higher yields than with the conventional farmer practice (maize monoculture, conventional tillage and residue removal).     

Changes in soil quality and plant available water capacity following systems re-design on commercial vegetable farms

Loss of ecological functions due to soil degradation impacts viability of crop production systems world-wide, particularly in vegetable cropping systems commonly located in the most productive areas and characterized by intensive soil cultivation. This paper reports soil degradation caused by intensive vegetable farming, and its reversibility after two to five years of drastic changes in soil management on 16 commercial vegetable farms in south Uruguay. Changes in soil management included addition of green manures and pastures in rotations of vegetable crops, use of animal manure, and erosion control support measures (terracing, reducing slope length, re-orientation of ridges). Soil degradation caused by vegetable farming was assessed by comparing soil properties in 69 vegetable fields with values at reference sites located close to the cropped fields. Effects of the changes in soil management in the 69 fields were assessed by comparing soil properties at the start and to those at the end of the project. Compared to the on-farm reference sites, the vegetable fields contained 36% less SOC, 19% less exchangeable potassium, water stable aggregates with an 18% smaller geometric mean diameter, and 11% lower plant-available soil water capacity. Phosphorus availability was 5 times higher under vegetable cropping compared to the on-farm reference. Phaeozems (Abruptic) revealed greater degradation (44% less soil organic carbon (SOC)) than Vertisols (24% less SOC) and Phaeozems (Pachic) (21% less SOC). After two to five years of improved soil management, SOC concentration in the upper 20 cm increased by on average 1.53 g kg⁻¹ (12%) in the Phaeozems (Abruptic) and 1.42 g kg⁻¹ (9%) in the Phaeozems (Pachic). SOC in Vertisols increased only by 0.87 g kg⁻¹, most likely due to their greater initial SOC concentration. Topsoil carbon sequestration was on average 3.4 Mg ha⁻¹ in the Phaeozems. Multiple linear regression showed the quantity of incorporated amendments, the initial amount of SOC and the clay content to explain 77% of the variability in yearly changes of SOC. Available water capacity increased significantly with SOC particularly due to more water retention at field capacity, resulting in an increase in available water capacity in the first 20 cm of soil of 8.4 mm for every 10 g kg⁻¹ of SOC increase. Results are discussed in relation to perspectives of soil degradation reversal in the long term.     

Optimized single irrigation can achieve high corn yield and water use efficiency in the Corn Belt of Northeast China

Decreasing the corn (Zea mays L.) gap between the potential yield and farm yield and reducing the risk of grain yield of drought are very important for corn production in the Corn Belt of Northeast China (CBNC). To achieve a high and stable corn yield, the effects of supplementary irrigation on yield, water use efficiency (WUE) and irrigation water use efficiency (IWUE) were studied using a modelling approach. The Root Zone Water Quality Model 2 was parameterized and evaluated using two years of experimental data in aeolian sandy soil and black soil. The evaluated model was then used to investigate responses to various irrigation strategies (rainfed, full irrigation and 12 single irrigation scenarios) using long-term weather data from 1980 to 2012. Full irrigation guarantees a high and stable corn grain yield (12.92 Mg ha⁻¹ and has a coefficient of variation (CV) of 14.8% in aeolian sandy soil; 12.30 kg Ma⁻¹ and CV of 11.1% in black soil), but has a low water use efficiency (19.92 and 21.81 kg ha⁻¹ mm⁻¹) and a low irrigation water use efficiency (10.01 and 11.03 kg ha⁻¹ mm⁻¹). A single irrigation can increase corn yields by 3–35% for aeolian sandy soil and 5–35% for black soil over different irrigation dates compared with no irrigation. The most suitable single irrigation date was during late June to early July for aeolian sandy soil (yield = 10.73 Mg ha⁻¹ and WUE = 27.94 kg ha⁻¹ mm⁻¹) and early to mid-July for black soil (yield = 11.20 Mg ha⁻¹ and WUE = 27.70 kg ha⁻¹ mm⁻¹). The lowest yield risk of falling short of the yield goal of 8, 9, and 10 Mg ha⁻¹ were 9.1%, 18.2%, and 33.33% in aeolian sandy soil and 3.0%, 15.25, and 21.2% in black soil when an optimized single irrigation was applied in late June or early July, respectively. Therefore, an optimized single irrigation should be applied in late June to early July with the irrigation amount to refill soil water storage of root zone to field capacity in CBNC.     

Effect of rainfall concentration with different ridge widths on winter wheat production under semiarid climate

Ridge and furrow rainfall concentration (RC) system has gradually been popularized to increase water availability to crops for improving and stabilizing agricultural production in the semiarid area of northwest China. The system is comprised of two elements: the plastic-covered ridge serves as rainfall harvesting zones and the furrow serves as planting zones. To make this system more perfect for alleviating drought stress in semiarid region, it is necessary to test optimum planting systems. A field experiment was conducted from 2007 to 2010 to evaluate the effects of RC planting on soil moisture, wheat yield and water use efficiency (WUE) under different ridge widths. Four planting systems were designed (RC₄₀: 40 cm ridge with 60 cm furrow width, RC₆₀: 60 cm ridge with 60 cm furrow width, RC₈₀: 80 cm ridge with 60 cm furrow width, and CF: conventional flat without ridging). The results showed that RC planting can significantly increase soil moisture in 0–200 cm during the growing seasons of winter wheat. The rainfall-harvesting effect increased with ridge width increasing. Winter wheat yield and WUE was significantly higher under RC₆₀ than under CF by 405.1 kg ha⁻¹ and 2.39 kg mm⁻¹ ha⁻¹, respectively, on average across the three experimental years (P < 0.05). The above findings indicate that RC₆₀ can benefit winter wheat cropping for higher yield through improving soil moisture. It could be concluded that the RC planting system with 60 cm ridge and furrow width will offer a sound opportunity for sustainable farming in semiarid dryland agricultural area.