Exploring integrated crop–livestock systems in different ecoregions of the United States

Large-scale, energy-intensive, specialized production systems have dominated agricultural production in the United States for the past half-century. Although highly productive and economically successful, there is increasing concern with unintended negative environmental impacts of current agricultural systems. Production systems integrating crops and livestock have potential for providing additional ecosystem services from agriculture by capturing positive ecological interactions and avoiding negative environmental outcomes, while sustaining profitability. A diversity of ecologically sound integrated crop-livestock systems have been and can be employed in different ecoregions: sod-based crop rotations, grazing cover crops in cash-crop rotations, crop residue grazing, sod intercropping, dual-purpose cereal crops, and agroforestry/silvopasture. Improved technologies in conservation tillage, weed control, fertilization, fencing, and planting, as well as improved plant genetics offer opportunities to facilitate successful adoption of integrated systems. This paper explores the use and potential of integrated crop-livestock systems in achieving environmental stewardship and maintaining profitability under a diversity of ecological conditions in the United States.     

Agroecological principles for the redesign of integrated crop–livestock systems

Combining crops and livestock within integrated crop–livestock systems (ICLS) represents an opportunity to improve the sustainability of farming systems. The objective of this paper is to analyse how agroecological principles can help farmers to redesign and improve the resilience, self-sufficiency, productivity, and efficiency of ICLS. Relying on case studies from Brazil and France, we examine how the transformation of two conventional, specialised systems into more integrated-production systems illustrates the different dynamics towards agroecological ICLS. The French case study, based on self-sufficient farming systems belonging to a sustainable agriculture network, highlights that cost-cutting management led to a win–win strategy comprising good economic and environmental performances. The farms decreased their dependence on external inputs and had only a limited loss of production. The past trajectories of the farms illustrate how increasing the interactions between subsystems improved the self-sufficiency and efficiency of the farms. The Brazilian case study compares slash-and-burn agriculture in the Amazonian region with the recovery of degraded grazing area by ICLS. A small increase in chemical inputs linked to a diversification of productions led to a large increase in production and a large decrease in environmental impacts (deforestation). The Brazilian case study also illustrates how the diversification of production increased the resilience of the system to market shocks. Reconstructing the links among soil, crops, and animals following agroecological principles could improve the different performances of ICLS. New agroecological ICLS, benefiting from diversified productions and increased interactions between subsystems, are likely to offset the trade-off between agricultural production and environmental impacts observed in current ICLS.     

Pasture grazing intensity and presence or absence of cattle dung input and its relationships to soybean nutrition and yield in integrated crop–livestock systems under no-till

In integrated soybean–beef cattle systems, the pasture grazing intensity affects the grain crop performance in succession. In addition, the dung cattle input influences the soil nutrients distribution in the field affecting the grain crop yield. This experiment aims to evaluate the effects of winter pasture heights and cattle dung input in soybean crop performance in succession. Main soil macronutrient content, soybean plant population, dry shoot biomass, plant height, plant nutrient content, soybean yield and yield components were assessed in the 10th experimental year. The experiment was conducted in the state of Rio Grande do Sul, Southern Brazil, in a long-term integrated crop–livestock systems implemented in 2001. Treatments were arranged in a split plot design with four pasture heights (0.10, 0.20, 0.30, and 0.40 m) and two levels of dung input (with or without). For all the variables analyzed, there was no interaction between pasture heights and cattle dung input (P > 0.05). The pasture height management had only effect in soil P content, soybean dry biomass production, plant height and number of grains per pod. The increase in grazing intensity was associated to the rise in soybean plant height and dry mass production but was without effect on grain yield. The presence of grazing animals in the integrated soybean–beef cattle systems, and the resultant augmentation of dung input increased by 122% and 38% the availability of soil K and P, respectively in relation to the absence. Thus, the content of such nutrients in the plant were increased in 41% and 7%, respectively. The improvement in soybean nutrition increases the amount of pods per plant by 20%, and resulting in a 23% increase in soybean yield. These results indicate that cattle dung input resulting from grazing animals in the pasture phase increased soybean grain yield due to better plant nutrition. Although, the occurrence of cattle dung was very concentrated in some spots of the field and thus future studies should address strategies to improve spatial distribution of cattle dung input.     

Crop and cattle production responses to tillage and cover crop management in an integrated crop–livestock system in the southeastern USA

Integrated crop–livestock systems can help achieve greater environmental quality from disparate crop and livestock systems by recycling nutrients and taking advantage of synergies between systems. We investigated crop and animal production responses in integrated crop–livestock systems with two types of winter cover cropping (legume-derived N and inorganic fertilizer N), two types of tillage [conventional disk (CT) and no tillage (NT)], and whether cover crops were grazed by cow/calf pairs or not. The 13-ha field study was a modification of a previous factorial experiment with four replications on Ultisols in Georgia, USA. Recurring summer drought severely limited corn and soybean production during all three years. Type of cover crop had little influence and grazing of cover crops had minor influence on crop production characteristics. Cattle gain from grazing of winter cover crops added a stable component to production. No-tillage management had large positive effects on corn grain (95 vs. 252 g m⁻² under CT and NT, respectively) and stover (305 vs. 385 g m⁻²) production, as well as on soybean grain (147 vs. 219 g m⁻²) and stover (253 vs. 375 g m⁻²) production, but little overall effect on winter wheat grain (292 g m⁻²) and stover (401 g m⁻²) production. Our results suggest that robust, diversified crop–livestock systems can be developed for impoverished soils of the southeastern USA, especially when managed under no tillage to control environmental quality and improve resistance of crops to drought.     

Integrated crop–livestock systems in the Brazilian subtropics

In the subtropical region of Brazil, integrated crop–livestock systems (ICLSs) are characterized by the annual rotation of pastures and crops in a no-till system where the pasture component is used to produce either meat or milk. These systems focus on integration within the farm rather than between farms, being characterized by alternating cropping and pasturing in the same area. Independent of the crop rotations possible in a subtropical environment, the main integrated farming system found was rotation or succession of summer crops (Glycine max, Zea mays, Phaseolus vulgaris or Oryza sativa) with winter annual grazing grasses (mixed or solely Avena strigosa and Lolium multiflorum) or successive natural pastures.The high variability of crop yield in the Brazilian subtropics (due to climate extremes) as well as associated high costs and low prices has encouraged farmers to integrate livestock into their enterprises as a low-risk diversification option. Long-term experiments have demonstrated the benefits of crop–livestock integration with respect to many aspects of the soil–plant–animal system. There is evidence that such a system is not only a livestock–agriculture combination but also a unique system reaching a new complexity threshold, resulting in emergent properties with novel functionalities, some of which have yet to be investigated. In addition to greater environmental gains with less vulnerability, there are higher yields and more financial gain by the farmer, compared to that in the use of monocultures or non-integrated livestock farming. We conclude that ICLSs in Subtropical Brazil provide the opportunity for intensification with sustainability.     

Evolution in crop–livestock integration systems that improve farm productivity and environmental performance in Australia

Australian farming systems have an enduring history of crop–livestock integration which emerged in the face of high climate variability, infertile soils and variable landscapes. Ley farming systems with phases of shorter annual legume pasture phases with cereal crops predominate but, emerging sustainability issues and the need to manage risk is driving ongoing innovation in crop–livestock integration. We discuss the recent evolution of selected innovations that integrate crop and livestock production and their impacts on farm productivity, sustainability and business risk. Dual-purpose use of cereals and canola (Brassica napus) for forage during the vegetative stage while still harvesting for grain is now practiced throughout southern Australia's cropping zone. This practice provides risk management benefits, diversifies crop rotations, reduces pressure on other feed resources and can significantly increase both livestock and crop productivity from farms by 25–75% with little increase in inputs. Sacrificially grazing crops when expected grain yield is low and/or livestock prices are attractive relative to grain provides further flexibility in crop–livestock management systems vital for business risk management in a variable climate. Replacing annual pastures with perennial pasture phases in rotation with crops can provide a range of benefits including improved hydrological balance to reduce dryland salinity, subsoil acidification and water-logging, provide a management tool for herbicide-resistant or problem weeds, improved soil nutrient and carbon stocks as well as increased livestock productivity by filling feed gaps. In some environments, integration of perennial forages in mixtures with cropping, such as alley cropping and inter-cropping, also provide options for improving environmental outcomes. These practices are all innovations that provide flexibility and enable tactical decisions about the mix of enterprises and allocation of land and forage resources to be adjusted in response to climate and price. We discuss these innovations in the context of the emerging constraints to crop–livestock integration in Australia including the continuing decline in labour availability on farms and increasing management skill required to optimise enterprise profitability.     

Management targets for continuously stocked mixed oat × annual ryegrass pasture in a no-till integrated crop–livestock system

Feeding livestock with cover crops can improve the efficiency and sustainability of integrated crop–livestock systems under no-till. However, no-till systems are based on permanent soil cover by organic material, so grazing livestock can compete for soil cover. Hence, managing stocking rates during the grazing period of the cultivated forage species is a key factor to assure enough herbage mass for maintaining long-term sustainable no-till systems. In this context, the objective of this study was to determine sward management targets for a continuously stocked mixed oat (Avena strigosa) × annual ryegrass (Lolium multiflorum) pasture in rotation with soybean in a no-till integrated crop–livestock system to determine the optimum balance between animal production and herbage mass for soil cover. The effects of sward height management on animal performance and herbage mass covers were evaluated. Treatments corresponded to four sward heights: 10, 20, 30 and 40 cm, maintained throughout the experimental period through continuous stocking and variable stocking rate, plus a no-grazing control area. Treatments were arranged in a randomized complete block design with three replications. Herbage mass and animal performance increased linearly with sward height, but weight gain per hectare decreased. Grazing efficiency fitted to a quadratic regression and conversion efficiency a logarithmic model. Equilibrium between grazing and conversion efficiencies was reached on swards managed at 20 cm, indicating that this sward height provided enough herbage mass to allow both animal performance and no-till crop demand for soil cover.     

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.     

Winter cover crop: the effects of grass–clover mixture proportion and biomass management on maize and the apparent residual N in the soil

The advantages and disadvantages of varying mixture proportion of crimson clover (Trifolium incarnatum L.) and Italian ryegrass (Lolium multiflorum Lam.), used as winter cover crops, and cover crop biomass management before maize sowing (Zea mays L.) were studied in a series of field experiments in Eastern Slovenia. Pure stands and mixtures of cover crops on the main plots were split into different cover crop biomass management subplots: whole cover crop biomass ploughed down before maize sowing, aboveground cover crop biomass removed before ploughing and sowing, or aboveground cover crop biomass removed before sowing directly into chemically killed residues.Cover crop and cover crop biomass management affected the N content of the whole aboveground and of grain maize yields, and the differences between actual and critical N concentrations in the whole aboveground maize yield. The whole aboveground and grain maize dry matter yields, and the apparent remaining N in the soil after maize harvesting, showed significant interaction responses to cover crop × management, indicating positive and negative effects. Crimson clover in pure stand provided high, and pure Italian ryegrass provided low maize dry matter yields and N content in the yields in all the observed methods of biomass management. However, within individual management, mixtures containing high proportions of crimson clover sustained maize yields and N contents similar to those produced by pure crimson clover. Considering the expected ecological advantages of the mixtures, the results thereby support their use.     

Responses of soil properties,root growth and crop yield to tillage and crop residue management in a wheat–maize cropping system on the North China Plain

Crop residue removal and subsoil compaction are limiting to yield improvement in the North China Plain (NCP). We conducted a field study composed of six consecutive crop growing seasons from 2010 to 2013 in Henan province, China, to determine responses of soil properties, crop root distribution and crop yield to tillage and residue management in a wheat–maize cropping system under irrigated conditions. Tillage practices comprised mouldboard ploughing (MP) to a depth of 15-cm, deep mouldboard ploughing (DMP) to a depth of 30-cm, and chisel ploughing (CP) to a depth of 30-cm. Crop residue management included crop residue retained (CRRet) and crop residue removed (CRRem). The results indicated that yields in DMP and CP increased by 6.0% and 7.3% for wheat and by 8.7% and 9.0% for maize, respectively, relative to MP. The CRRet treatment also increased wheat yield by 6.7% and maize yield by 5.0%. The yield increases under DMP and CP were related to reduced bulk density and soil penetration resistance, increased soil water content, improved total N distribution and improved root density (0–60-cm). Compared with MP, the root mass density under DMP and CP were increased by 43.4% and 42.0% for wheat and by 40.6% and 39.4% for maize, respectively. The yield increases under CRRet were also related to increased soil water content, reduced penetration resistance and increased N status (0–40-cm). Overall, for DMP + CRRet and CP + CRRet, a more favorable soil environment alongside greater root mass density and suitable spatial distribution resulted in higher grain yields of wheat and maize. Thus, compared with conventional shallow tillage practice, DMP or CP with residue application could improve soil quality and agricultural productivity under irrigated areas with loam soil in the NCP.     

White lupine as a beneficial crop in Southern Europe. II. Nitrogen recovery in a legume–oat rotation and a continuous oat–oat

One experiment lasting for two years was carried out at Pegões (central Portugal) to estimate the impact of mature white lupine residue (Lupinus albus L.) on yield of fodder oat (Avena sativa L. cv. Sta. Eulalia) as the next crop in rotation, comparing with the continuous cultivation of cereal, under two tillage practices (conventional tillage and no-till) and fertilized with five mineral nitrogen (N) rates, with three replicates. Oat as a first crop in the rotation provided more N to the agro-ecosystem (63 kg N ha⁻¹) than did lupine (30–59 kg N ha⁻¹). This was at a cost of 100 kg of mineral N ha⁻¹, whereas lupine was grown without addition of N. A positive response of oat as a second crop was obtained per kg of lupine-N added to the system when compared with the continuous oat–oat. The cereal also responded positively to mineral N in the legume amended soil in contrast with the oat–oat sequence where no response was observed, partly due to the fast mineralization rate of lupine residue and a greater soil N immobilization in the continuous oat system. Each kg N ha⁻¹ added to the soil through the application of 73 kg DM ha⁻¹ mature lupine residue (above- and belowground material) increased by 72 kg DM ha⁻¹ the oat biomass produced as the second crop in rotation when 150 kg mineral N ha⁻¹ were split in the season, independent of tillage practice. Mature legume residue conserved in the no-tilled soil depressed the yield of succeeding cereal but less than the continuous oat–oat for both tillage practices, where the application of mineral N did not improve the crop response.     

Comparison of haploid Tuberosum-Solanum chacoense versus Solanum phureja-haploid Tuberosum hybrids as staminate parents of 4x–2x progenies evaluated under distinct crop management systems

The relative value of haploid Tuberosum-Solanum chacoense (TCH) vs. Solanum phureja-haploid Tuberosum (PTH) hybrids as male parents in 4x–2x crosses was estimated under two distinct crop management systems. The first experiment (E#1) was carried out with supplementary irrigation (three times a week) at Hancock-Wisconsin (WI) with 27 families derived from a sub-set of crosses involving 11 tetraploid (4x) cultivars and 10 diploid (2x) clones (3 TCH; 6 PTH; and one TCH-PTH hybrid clone). A second experiment (E#2) was conducted at Rhinelander-WI with the same group of families but it was only rainfed with no supplementary irrigation being provided during the entire course of the assay. For comparison, a complete set of 4x and 2x clones (used as parents) was also planted in each location. Three traits were evaluated in both locations: total tuber yield (TTY), haulm maturity (HM), and plant vigor (PV). Altogether, 18 out of 27 and 10 out of 27 families outyielded the corresponding 4x parents at E#1 and E#2, respectively. Significant differences among all 4x–2x families and among families of the TCH group were observed for TTY at both locations. No difference was found for TTY among families of PTH and [TCH–PTH] groups at each location. A total of 75% and 50% of the TCH families outyielded their 4x parents at E#1 and E#2, respectively. The percentage of families from the PTH group that outyielded their 4x parents at E#1 and E#2 was 83.3% and 25%, respectively. The TCH group had on average lower HM scores than PTH (at both locations) indicating some segregation for earliness. However, the HM values of the 4x–2x families were, in general, higher than those observed for the 4x parents. For PV, the PTH group mean was significantly higher than TCH group only in E#1. The PV values of the 4x–2x families were higher than the 4x-parent group at both locations. Our results indicated that TCH hybrids might be as good parents as PTH to increase the TTY of 4x–2x progenies. In addition, the TCH families displayed a slight higher level of performance under more stressful growing conditions than PTH hybrids as indicated by the assay at Rhinelander. Therefore, selection of genetic materials with potential broad range of adaptation seems to be feasible with both hybrids via the 4x–2x breeding scheme. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Construction of a crop—wild hybrid population for broadening genetic diversity in cultivated sunflower and first evaluation of its combining ability: the concept of neodomestication

The genetic base of sunflower elite lines is very narrow, due to many years of selection and breeding. To broaden the genetic diversity of the cultivated sunflower, in 1995 73 wild sunflower populations were crossed with 3 cultivated lines (Testers), and 219 hybrid offspring’s were evaluated in the field. GCA and SCA effects were computed suggesting for all traits a genetic potential for improvement through selection. Study of the hybrids revealed that the wild accessions bear different genetic abilities to combine with the testers for traits of morphological architecture, phenology and yield (seed weight and seed oil). The variance due to GCA and SCA showed that gene action was additive for days to flowering, branching and plant height. Genotypes derived from the same geographic origin may have either good or poor general combing ability. The correlation between GCA and per se genotype performance was positive for all traits except for seed oil content. This was the first attempt to evaluate wild-cultivated hybrids in sunflower on a large scale and will be the starting point for the management of hybrid Helianthus annuus populations for breeding. GCA and SCA estimations will facilitate the definition of strategies to manage and exploit the natural diversity for this crop.     

Productivity and profitability of cotton–wheat system as influenced by relay intercropping of insect resistant transgenic cotton in bed planted wheat

Cotton (Gossypium hirsutum L.) is the leading cash crop being grown across the globe including Pakistan. By the inclusion of insect resistant transgenic cotton (BT cotton), the cotton production has mounted many folds in Pakistan. BT cotton is mostly grown in Southern Punjab in cotton–wheat cropping system of Pakistan; however there exists a time conflict among wheat harvest and BT cotton sowing in this system. Wheat is harvested during late April but the ideal sowing time of BT cotton is early-mid March indicating a time conflict of 4–6 weeks which is becoming the main concern leading to wheat exclusion from this system. Intercropping of BT cotton in standing wheat is one of the possible options to manage this overlapping period. This two year field study was, therefore, conducted at two locations (Multan, Vehari) to evaluate the economic feasibility of relay intercropping of BT cotton through different sowing methods in BT cotton–wheat cropping system. BT cotton–wheat cropping systems included in the study were: conventionally tilled cotton (CTC) on fallow land during early and late March, CTC during late April after harvest of flat sown wheat (FSW), bed sown wheat (BSW) + intercropped cotton during early and late March, and ridge sown wheat (RSW) + intercropped cotton during early and late March. Planting cotton in fallow land with conventional tillage during early March had more seed cotton yield; whereas planting in the same way during April after wheat harvest had minimum seed cotton yield. Likewise, FSW had more yield than ridge and bed sown wheat with intercropped BT cotton during early or late March. However, the system productivity in terms of net income, benefit: cost ratio and marginal rate of return of BSW + intercropped BT cotton during early March was the highest during both years at both locations. However, the system with sole crop of BT cotton sown on fallow land during late or early March was the least economical even than the system with CTC during late April after harvest of FSW. In conclusion, BSW + intercropped cotton during early March may be opted to manage the time conflict and improve the economic productivity of BT cotton–wheat cropping system without wheat exclusion from the system.     

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.     

Towards a geography of queer temporalities: Time,space and rural–urban migrant gay men's exploration of sexuality in China

Building on the geography of sexualities and queer temporality studies, this research investigates the entanglement of sexuality, time and space with a case study of rural–urban migrant gay men in China. Based on participant observations and in-depth interviews with 46 Chinese rural–urban migrant gay men, we identify three forms of queer temporality – queer biographical time, queer life stage, and queer clock time – emerging from Chinese gay men's life stories. We also demonstrate how these different forms of queer temporality are conditioned by and influence certain spatial practices among our informants. In doing so, this analysis contributes to the geographical research on sexuality by challenging the rural/urban dichotomy in the existing literature on the one hand, and exploring the possibilities for a geography of queer temporality on the other.     

Is time to flowering in wheat and barley influenced by nitrogen?: A critical appraisal of recent published reports

The literature includes a number of reports, relating to both crop and non-crop species, showing conflicting responses of developmental plasticity to nitrogen availability. We reviewed 1130 papers published from 1990 to 2010 drawn from 14 agriculture-themed journals and conducted a critical appraisal of the effects of fertiliser nitrogen on time to heading or anthesis in barley and wheat, species for which there is a good deal of data. Features of the analysis were the use of relative responses (respect to unfertilised controls) of yield and time to flowering to nitrogen as a proxy for crop nitrogen status and developmental differences, respectively, and the standardisation of the start point for calculating time (in both calendar and thermal units) to flowering in autumn-sown winter cultivars to March 1 (N Hemisphere). The resulting database (180 cases) covered a broad range of unfertilised crop yields (1–8 Mg ha⁻¹), and times to flowering (47–168 days). In very few cases (19 out of 118), the relative time to flowering in fertilised crops differed by more than 5% from those of unfertilised crops across a range of yield responses to fertiliser nitrogen from negligible to three-fold. Currently available evidence does not provide solid support to a plastic response of time to flowering to nitrogen in these two species.