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.     

Combined application of nitrogen and phosphorus to enhance nitrogen use efficiency and close the wheat yield gap on varying soils in semi‐arid conditions

A primary driver of the wheat yield gap in Australia and globally is the supply of nitrogen (N) and options to increase N use efficiency (NUE) are fundamental to closure of the yield gap. Co‐application of N with phosphorus (P) is suggested as an avenue to increase fertiliser NUE, and inputs of N and P fertiliser are key variable costs in low rainfall cereal crops. Within field variability in the response to nutrients due to soil and season offers a further opportunity to refine inputs for increased efficiency. The response of wheat to N fertiliser input (0, 10, 20, 40 and 80 kg N ha^‐1) under four levels of P fertiliser (0, 5, 10 and 20 kg P ha^?1) was measured on three key low rainfall cropping soils (dune, mid‐slope and swale) across a dune‐swale system in a low rainfall semi‐arid environment in South Australia, for three successive cropping seasons. Wheat on sandy soils produced significant and linear yield and protein responses across all three seasons, while wheat on a clay loam only produced a yield response in a high rainfall season. Responses to P fertiliser were measured on the sandy soils but more variable in nature and a consistent effect of increased P nutrition leading to increased NUE was not measured.     

褐潮土长期定位不同施肥制度土壤生产功能演化研究

通过14年长期定位试验研究了褐潮土不同施肥制度对土壤生产功能、产量可持续性指数及农学效率的影响。结果表明，N、P为褐潮土作物高产的主要限制因子，14年产量平均，NPK比CK、N、NK、PK分别增产459%、386%、280%、205%（小麦）和154%、108%、87%、78%（玉米）；NPK+M(NPK配施厩肥)比NPK平均增产12%，NPK+S(NPK加秸秆)与NPK产量相当。NPK及NPK配施有机肥（包括厩肥和秸秆）处理的小麦、玉米产量可持续性指数高于N、P不均衡施用处理。化肥肥效因作物种类、施肥组合而不同，N肥单施时小麦和玉米N的农学效率降低，而NPK配施时N的农学效率有上升趋势，平均分别为16 kg/kg N（小麦）和14 kg/kg N（玉米）；磷肥肥效具有短期的叠加效应，P的农学效率小麦大于玉米，种植10年后P的农学效率最高可达最初的4.5～7倍；K的农学效率在试验进行十年后NK处理平均为负值，同期NPK处理中小麦K的农学效率却急剧增加，K成为作物高产的限制因素；有机肥对小麦和玉米的农学效率分别为21 kg/t和25 kg/t，秸秆对小麦和玉米的农学效率分别为负值和37 kg/t。NPK均衡施肥能提高土壤有机质、全N、全P、速效N、速效P等肥力指标；NPK配施有机肥能加快土壤有机质和N、P、K养分的积累；NPK不均衡施肥导致土壤中此种营养元素的耗竭。     

不同施肥结构的增产效应和对小麦籽粒品质的影响

１３年的定位监测研究结果表明，不同施肥结构对小麦、玉米两熟制轮作的年产量影响明显，各处理总的产量趋势是：ＭＮＰＫ＞ＭＮＰ＞ＭＮ＞ＮＰＫ＞ＮＰ＞Ｍ＞Ｎ＞ｃｋ。基础地力的产量效应为３７．９％，肥料的增产效应为６２．１％；肥料增产效应中，化肥占７５．８％，有机肥占２４．２％，显示出化肥为主要增产途径；在化肥的增产效应中，Ｎ的增产效应为７０．６％，Ｐ为２３．５％，Ｋ为５．９％；以ＭＮＰＫ处理的产量和小麦籽粒蛋白质含量最高，这说明有机肥与无机肥配合施用，可使作物高产优质，土壤有机质含量得到提高。     

Long-term effects of crop rotation,manure and mineral fertilisation on carbon sequestration and soil fertility

Carbon sequestration, recently advocated to mitigate climate change, needs a thorough knowledge of the dynamics of soil organic carbon (SOC), whose study requires long-term experiments. A field trial started in 1967 is still in progress in the Southeast Po valley (Italy). It compares a 9-year rotation (corn–wheat–corn–wheat–corn–wheat–alfalfa–alfalfa–alfalfa), two 2-year successions (corn–wheat and sugarbeet–wheat), continuous corn and continuous wheat. During the first 18 years (up to 1984) wheat crops were always followed by catch crops of silage corn. Within each rotation, three rates of cattle manure have been factorially combined with three mineral NP rates. In 1984 the highest manure application was stopped. Wheat straw and corn stalks have always been removed from the field. Since 1972 up to now every year we have determined the organic C and total N contents in soil samples collected from 0.40-m depth. During the first 18 years (in the presence of the catch crop) SOC exponentially declined, probably as a consequence of the intensification of tillage depth and crop succession with respect to the previous conventional agriculture. The intensification regarded ploughing, which became deeper, the number of cropped species that in most treatments was reduced, and mineral N application, which, on average, increased. The drop was faster in the sugarbeet–wheat succession than in the 9-yr rotation and continuous wheat. After 1985, without the catch crop, SOC linearly increased, faster in the 9-yr rotation and continuous wheat than in sugarbeet–wheat. The results can be ascribed to the amount and C/N ratio of debris remaining in the field after each crop, even after having taken away wheat straw and corn stalks. The debris consisted of sugarbeet tops, with a low C/N ratio, and of roots and basal culms of the two cereal crops with higher C/N ratio. Mineral fertilizers significantly increased SOC, probably for the greater amount of cereal roots and sugarbeet tops in more fertilized plots. The influence of manure was less intense, but its benefits lasted longer than 18 years after its interruption. Soil N content was more related to accumulated organic matter than to mineral N fertilisation. In conclusion the highest C sequestration was obtained with manure addition, with the highest rate of mineral fertilizers, and in the rotation containing the alfalfa ley. The effects of these factors were not additive.     

Applications of Foliar Fertilizers Containing Glycinebetaine Improve Wheat Yields

Nitrogen availability and drought influence wheat (Triticum aestivum L.) grain yields in the semiarid and subhumid Pampas region of Argentina. The application of fertilizers containing osmoprotectants, such as glycinebetaine, to crop canopies might reduce crop losses caused by environmental stresses. The objectives of this study were (a) to determine the effects on wheat grain yields of the foliar application of a commercial fertilizer with glycinebetaine, and (b) to establish, under farmers’ field conditions, the relation between soil properties and the productivity of wheat crops treated with the same product. Two experiments were conducted in the north‐western part of the Buenos Aires province of Argentina on Typic Hapludolls and Entic Hapludolls. In the first, the treatments were N fertilization (0, 23 and 46 kg ha^?1) and the foliar application to the wheat crop, in the vegetative stages, of a foliar fertilizer containing N, P, Zn and glycinebetaine (0 and 2.5 l ha^?1). The second experiment was carried out on 10 farmers’ fields, for each of which the treatment was the foliar application to the wheat crop, in the vegetative stages, of the same foliar fertilizer (0 and 2.5 l ha^?1). In both experiments, the grain yield, the individual grain weight, the number of grains per spike and the spike and plant density at the physiological maturity of the crops were determined. Soil organic matter (SOM) and available P were determined in each of the 10 fields of the second experiment. Wheat grain yields were increased by N fertilization and glycinebetaine treatment. The number of grains per spike was higher in the treatments with glycinebetaine application. In the farmers’ fields, the grain yields of the treatments with the application of the product with glycinebetaine were, on average, 18 % higher than those of the non‐treated plots, with greater responses at sites with low SOM levels. We conclude that, in subhumid regions with a dry period between the tillering and flowering stages of wheat, the foliar application of foliar fertilizers containing glycinebetaine at the vegetative stages of crop development enhances grain yields by increasing the number of grains per spike. This response is independent of the SOM level or the N fertilization rate.     

Cropping System Affects Polymer‐Coated Urea Release and Corn Yield Response in Claypan Soils

Preplant‐applied, urea‐based fertilizer management in high‐residue, no‐till (NT) corn (Zea mays L.) is challenging because of potential N loss due to cool, wet conditions in the spring and dry conditions during the summer months. Field research evaluated the effects of polymer‐coated urea (PCU) application timing, placement and cropping system on urea release for corn and determined corn yield response to PCU on claypan soils following wheat (Triticum aestivum L.) cropping systems [reduced‐till corn following wheat, no‐till corn following wheat with double‐cropped (DC) soybean [Glycine max (L.) Merr.] and no‐till corn following wheat with a frost‐seeded red clover (FSC) (Trifolium pratense L.) cover crop]. Urea release from PCU was <35 % from fall through winter (November–January) and <20 % for early preplant (February–March) applications until 1 April. By 1 August, less urea was released in some instances from surface applications of PCU following FSC or DC soybean, but release was generally greater than in the absence of soil. No‐till corn following DC soybean or FSC had yields that were 1.01–1.32 Mg ha^?1 greater when grown with PCU compared to urea at 168 kg N ha^?1. Grain yields were similar within no‐till cropping systems with PCU, anhydrous ammonia and sidedressed urea ammonium nitrate (UAN) at 168 kg N ha^?1. Farmers should recognize that high yields may not be obtained if PCU rates are reduced by 50 % (84 kg N ha^?1) in high‐residue (DC soybean or FSC), no‐till production systems. Several N sources such as PCU, anhydrous ammonia and sidedressed UAN worked similarly in high‐residue, no‐till systems, although no differences between N sources were observed in a reduced‐tillage system.     

Straw management, crop rotation, and nitrogen source effect on wheat grain yield and nitrogen use efficiency

Nitrogen fertilizer management from different sources and annual crop rotations are important components of wheat (Triticum aestivum L.) production systems, especially where air and soil quality issues have prompted a search for alternatives to wheat straw burning. This study examined the effects of two different wheat straw management options (burning and incorporation by tillage), three crop rotations [wheat-sesbania (Sesbania spp.), wheat–maize (Zea mays L.), and wheat-clean fallow] and three N sources (urea, chicken manure, and urea plus chicken manure) on wheat grain yield and N use efficiency. The experiment was conducted as split–split plot treatment arrangement with three replications for eight wheat cropping seasons in the state of Sonora, Mexico. Results indicated that both wheat grain yield and N use efficiency were higher with burning than incorporation of wheat straw and with fertilization with urea or urea plus chicken manure than chicken manure alone. As shown by the crop rotation-by-straw management interaction, planting sesbania following incorporation of the straw by tillage produced comparable grain yields to straw burning treatment. In contrast, wheat in annual rotation with maize produced the lowest wheat grain yield and N use efficiency irrespective of the wheat straw management and N source applied.     

Effects of crop residue management on winter durum wheat productivity in a long term experiment in Southern Italy

A long-term experiment comparing different crop residue (CR) managements was established in 1977 in Foggia (Apulia region, southern Italy). The objective of this study was to investigate the long-term effects of different types of crop residue management on main yield response parameters in a continuous cropping system of winter durum wheat. In order to correctly interpret the results, models accounting for spatial error autocorrelation were used and compared with ordinary least square models.Eight crop residue management treatments, based on burning of wheat straw and stubble or their incorporation with or without N fertilization and irrigation, were compared. The experimental design was a complete randomized block with five replicates.Results indicated that the dynamics of yield, grain protein content and hectolitric weight of winter durum wheat did not show any decline as usually expected when a monoculture is carried out for a long time. In addition, the temporal variability of productivity was more affected by meteorological factors, such as air temperature and rainfall, than CR management treatments. Higher wheat grain yields and hectolitric weights quite frequently occurred after burning of wheat straw compared with straw incorporation without nitrogen fertilization and autumn irrigation and this was attributed to temporary mineral N immobilization in the soil. The rate of 50 kg ha⁻¹ of N seemed to counterbalance this negative effect when good condition of soil moisture occurred in the autumn period, so yielding the same productive level of straw burning treatment.     

Maize Grain Yield Response to Tillage and Fertilizer Nitrogen Rates on a Tara Silt Loam

Effects of tillage on the appropriate fertilizer N applications needed to achieve maximal grain yield are poorly denned. The study objective was determination of relative corn grain yield response to N application rate for four tillage practices: no-tillage (NT), ridge tillage (RT), fall chisel plowing (CP) and fall moldboard plowing (MP). Maize (Zea mays L.) grain yield and N accumulation were monitored over a 6 year period with the same tillage treatment and the same fertilizer N rate applied each year to each plot. Two hybrids, differing in relative maturity rating, were planted each year. Fertilizer N rates ranged from 10 to 190 kg ha^?1 and consisted of 10 kg ha^?1 of liquid starter N applied at planting with varying amounts of fall applied anhydrous ammonia. With only starter fertilizer, grain yields increased with tillage intensity in the order NT ≤ RT ≤ CP ≤ MP. With ≥ 55 kg total applied Nha^?1, 6 year average grain yields were unaffected by tillage. Total N removed in grain annually with only starter fertilizer ranged from 25–85 kg ha^?1 Maximal amounts of N removed, about 145 kg N ha^?1, occurred with 100–145 kg applied N ha^?1 for all tillage treatments under the more favorable climatic conditions. Several interactions affecting grain yield appear climatically sensitive with exception of tillage by fertilizer N interactions. Because of variability in climate, planting dates varied by almost 4 weeks. Relative yield loss due to planting delay were Fertilizer N (mean change ??124 –?275 kg ha^?1 day^?1) > Starter N only and MP (mean ?? 259 kg ha^?1 day^?1) > other tillages in general. Yield loss due to delayed planting ranged from 0.0–275 kg ha^?1 day^?1. Grain yield gains due to early spring soil temperatures were 16.0–21.8 kg ha^?1 index-degree^?1 with MP tillage and averaged 2.7– 16.7 kg ha^?1 index-degree^?1 more than those of other tillage-hybrid combinations.     

The effect of tillage system and residue management on grain yield and nitrogen use efficiency in winter wheat in a cool Atlantic climate

The effects of soil tillage and straw management systems on the grain yield and nitrogen use efficiency of winter wheat (Triticum aestivum L. em. Thell.) were evaluated in a cool Atlantic climate, in central Ireland between 2009 and 2011. Two tillage systems, conventional tillage (CT) and reduced tillage (RT) each with and without incorporation of the straw of the preceding crop, were compared at five levels of fertiliser N (0, 140, 180, 220 and 260 kg N ha⁻¹).CT had a significantly higher mean grain yield over the three years but the effect of tillage varied between years. Yields did not differ in 2009 (Year 1), while CT produced significantly higher grain yields in 2010 (Year 2), while RT produced the highest yields in 2011 (Year 3). Straw incorporation had no significant effect in any year.Nitrogen application significantly increased the grain yields of all establishment treatment combinations. Nitrogen use efficiency (NUE) ranged from 14.6 to 62.4 kg grain (85% DM) kg N ha⁻¹ and decreased as N fertiliser rate was increased.The CT system had a significantly higher mean NUE over the three years but the effect of tillage varied with years. While there was no tillage effect in years 1 and 3, CT had a significantly higher NUE than RT in year 2. Straw management system had minimal effect on NUE in any year.The effect of tillage and N rate on soil mineral N content also varied between years. While there was no tillage effect in years 1 and 3, RT had significantly larger soil N contents than CT in the spring before N application, and post-harvest in year 2. N application rates had no effect on soil N in year 1, increased residual N content in year 2 and had an inconsistent effect in year 3. Straw management had no significant effect on soil mineral N content.These results indicate that RT establishment systems can be used to produce similar winter wheat yields to CT systems in a cool Atlantic climate, providing weather conditions at establishment are favourable. The response to nitrogen is similar with both tillage systems where the crop is successfully established. Straw management system has very little effect on crop performance or nitrogen uptake.     

Conservation Agriculture practices reduce the global warming potential of rainfed low N input semi-arid agriculture

Conservation tillage and crop rotations improve soil quality. However, the impact of these practices on greenhouse gas (GHG) emissions and crop yields is not well defined, particularly in dry climates. A rainfed 2-year field-experiment was conducted to evaluate the effect of three long-term (17–18 years) tillage systems (Conventional Tillage (CT), Minimum Tillage (MT) and No Tillage (NT)) and two cropping systems (rotational wheat (Triticum aestivum L.) preceded by fallow, and wheat in monoculture), on nitrous oxide (N₂O) and methane (CH₄) emissions, during two field campaigns. Soil mineral N, water-filled pore space, dissolved organic carbon (C) and grain yield were measured and yield-scaled N₂O emissions, N surplus and Global Warming Potentials (GWP) were calculated. No tillage only decreased cumulative N₂O losses (compared to MT/CT) during campaign 1 (the driest campaign with least fertilizer N input), while tillage did not affect CH₄ oxidation. The GWP demonstrated that the enhancement of C stocks under NT caused this tillage management to decrease overall CO₂ equivalent emissions. Monoculture increased N₂O fluxes during campaign 2 (normal year and conventional N input) and decreased CH₄ uptake, as opposed to rotational wheat. Conversely, wheat in monoculture tended to increase soil organic C stocks and therefore resulted in a lower GWP, but differences were not statistically significant. Grain yields were strongly influenced by climatic variability. The NT and CT treatments yielded most during the dry and the normal campaign, and the yield-scaled N₂O emissions followed the same tendency. Minimum tillage was not an adequate tillage management considering the GWP and the yield-scaled N₂O emissions (which were 39% lower in NT with respect to MT). Regarding the crop effect, wheat in rotation resulted in a 32% increase in grain yield and 31% mitigation of yield-scaled N₂O emissions. Low cumulative N₂O fluxes (<250 g N₂O-N ha⁻¹ campaign⁻¹) highlighted the relevance of soil organic C and CO₂ emissions from inputs and operations in rainfed semi-arid cropping systems. This study suggests that NT and crop rotation can be recommended as good agricultural practices in order to establish an optimal balance between GHGs fluxes, GWP, yield-scaled N₂O emissions and N surpluses.     

醚苯磺隆在小麦田的除草效果及其残留对后茬作物的安全性

小麦返青期,在河北省小麦-夏播作物一年两熟地区冬小麦田施用醚苯磺隆,对其除草效果及其在土壤中的残留在不同耕作方式下对后茬作物生长和产量的影响进行了研究。结果表明:10%醚苯磺隆可湿性粉剂对小麦田主要阔叶杂草有较好的防除效果,对小麦产量无影响。10%醚苯磺隆在小麦田的施药剂量为60 g/hm2,对下茬作物玉米、谷子幼苗的生长及产量无影响,对大豆、花生、油菜的药害轻;随用药剂量增加药害加重,480 g/hm2处理对下茬参试作物均有较重的药害,不同作物对醚苯磺隆在土壤中残留量的敏感性有差异,其顺序为:油菜>大豆>花生>谷子>玉米。播种前进行旋耕比免耕对后茬参试作物幼苗生长及大豆和油菜产量影响要轻。     

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).     

Growth and Yield of Sweet Corn Following Green Manure in a Warm Temperate Environment on Sandy Soil

Legumes used as green manure (GMN) may provide on‐farm sources of N for subsequent crops. In warm‐humid climates on sandy soils, however, there is a need to evaluate effects on growth and yield of subsequent crops when GMN substitutes for chemical N fertilizer. We collected time‐series data for 2 years to evaluate growth and ear yield response of sweet corn (Zea mays L. var. Rugosa) in annual rotation with GMN (summer, winter or summer plus winter GMN) and supplemented with 0, 67 or 133 kg chemical N ha⁻¹. Control treatments receiving 0, 67, 133, 200 or 267 kg chemical N ha⁻¹ were used for comparison. Rotation with summer plus winter GMN resulted in more growth and yield benefit for sweet corn than did the other GMN rotations. Compared with control treatments receiving the same chemical N rates, rotation with summer plus winter GMN increased sweet corn ear yield, leaf area index and total plant dry weight and N content by 15–30 %. Despite these benefits, use of high chemical N rate (267 kg chemical N ha⁻¹) resulted in ear yields at least 20 % greater than sweet corn rotated with any GMN and fertilized with reduced N rates. Largest increases in sweet corn dry weight and N content occurred between 4 and 6 weeks after emergence in all treatments. After this period of rapid growth, sweet corn fertilized with 267 kg chemical N ha⁻¹ showed higher N content than all other treatments. Prior to this period of rapid growth, multiple rainfall events in excess of 30 mm may have resulted in leaching of N from GMN residue. Considering the high rainfall levels, low water and N retention capability of sandy soils and rapid N release from GMN during decomposition, future research of GMN in this environment should evaluate options to better match GMN termination with time of greatest potential N uptake from a subsequent crop.     

不同降水年型旱地小麦休闲期耕作的蓄水增产效应

为明确旱地小麦通过休闲期耕作实现蓄水增产的技术途径, 2009-2012年连续3个小麦生长季, 在山西闻喜县进行了休闲期深翻、深松或无耕作的田间试验, 以明确不同耕作措施对土壤水分变化、小麦产量形成的影响。结果表明, 深翻和深松处理播种期0~300 cm土壤蓄水量增加, 枯水年增加63~91 mm, 平水年增加41~70 mm, 丰水年增加54~74 mm, 尤其在枯水年和丰水年生育后期蓄水效果仍显著, 休闲期土壤蓄水效率显著提高, 枯水年提高147%~205%。深翻和深松处理在枯水年和丰水年可促进小麦生育后期吸收300 cm土层土壤水分, 使产量和产量构成因素显著提高, 尤其在枯水年产量提高34%~45%。在平水年, 穗数、穗粒数和产量显著提高, 且在平水年和丰水年深翻和深松处理对产量构成因素中的穗数影响最大。深翻和深松处理后降水生产效率和水分利用效率显著提高。不同降水年型休闲期耕作条件下, 穗数与播种至拔节期120~180 cm、拔节至开花期60~120 cm土层土壤贮水减少量关系密切, 穗粒数与播种至拔节期60~120 cm土层关系密切, 产量与拔节至开花期60~120 cm、开花至成熟期 120~180 cm土层关系密切。总之, 在本研究条件下, 旱地小麦休闲期深翻或深松耕作有利于蓄积休闲期降水, 改善底墒, 尤其枯水年的效果更为明显; 有利于增加土壤水分, 促进小麦向深层吸收土壤水分, 优化产量构成, 实现增产。在枯水年和平水年, 以休闲期深翻效果较好, 在丰水年以休闲期深松效果较好。     

Decreased foliar nitrogen and crop yield in organic rainfed almond trees during transition from reduced tillage to no-tillage in a dryland farming system

Sustainable farming practices can be beneficial or detrimental to crop production in the short-term, which will strongly determine their appeal to farmers. We evaluated the effects of several sustainable practices on soil properties, plant nutrition and ecophysiology and crop yield in a semiarid agroecosystem. A three-year randomised experiment was conducted in a rainfed almond grove where the initial soil management was reduced tillage. Two alternative treatments were evaluated: reduced tillage plus green manure and no-tillage. The following soil and plant parameters were measured once per year: soil organic carbon, total nitrogen and P_olsen; foliar N, P, δ¹³C and δ¹⁵N and crop yield. We found that soil bulk density increased significantly with no-tillage. Leaf δ¹⁵N was positively associated with soil fertility, foliar nutrient concentrations and crop yield across treatments. Leaf δ¹³C, N_foliar and crop yield were strongly positively associated across treatments in every year of the study. Reduced tillage treatments displayed higher leaf δ¹⁵N, δ¹³C, N_foliar and crop yield than the no-tillage treatment, indicating a sharp decrease in the leaf nitrogen status and intrinsic water use efficiency of almond trees during the transition from reduced tillage to no-tillage. In semiarid agroecosystems where soils are prone to compaction, some tillage is required to maintain optimal crop production in rainfed almonds.     

Long-Term Effects of Fertilizers on the Soil Fertility and Productivity of a Rice–Wheat System

Rice–wheat cropping system to which graded levels of NPK fertilizers had been applied for 20 years were compared for yield trends, and changes in response function, soil organic-C and available N, P, K and S status. This study of system in which only chemical fertilizers had been used over a long period enabled long-term yield declines of rice and wheat at different levels and combinations of NPK fertilizers to be evaluated. The highest rate of yield decline in both rice and wheat was found when 120 kg ha⁻¹ N was applied alone. The lowest rate of decline was observed when all three nutrients (N, P and K) were applied, at 40, 35 and 33 kg ha⁻¹ for N, P and K, respectively, followed by 120, 35 and 33 kg ha⁻¹ (currently recommended levels). The yield response of rice and wheat to N fertilizer declined over the 20 years, with a higher rate of decline in wheat. In contrast, the response to applied P and K increased with time in both crops, with a higher response rate in wheat. With continuous application of N and P fertilizers, there was a marginal change in available N and K in the soil over time, but an approximately 3-fold increase in available P and an approximately 2-fold increase in available S were obtained by regular dressing of P fertilizer (SSP: 7 % P, 12 % S) over 20 years. The results revealed that balanced, high doses of NPK fertilizers are required to maintain soil fertility and raise grain yields.     

淮北砂姜黑土地力贡献与培肥技术研究

对杨柳点长期定位培肥试验和相关小麦施肥试验资料进行分析,结果表明：地力贡献与小麦施肥产量、地力贡献率之间呈线性正相关,高产田块地力贡献在小麦施肥产量中占主要地位。砂姜黑土地力贡献主要受土壤有机质和速效磷含量的影响,速效钾含量尚不是限制因子。长期连续施肥条件下,不同的土壤养分指标受有机无机配比的影响不同。有机质和氮素养分含量偏低的土壤,要通过增施有机肥加以培肥,磷素或钾素养分偏低的土壤可以通过增施有机肥或化肥来培肥。     

Landscape Position and Precipitation Effects on Spatial Variability of Wheat Yield and Grain Protein in Southern Italy

Wheat yield and protein content are spatially variable because of inherent spatial variability of factors affecting the yield at field scale. In Mediterranean environments, yield variability is often caused by the irregular weather pattern, particularly rainfall and by position on the landscape. The objective of this study was to determine the effects of landscape position and rainfall on spatial variability of wheat yield and protein in a rolling terrain field of Southern Italy, and to propose stable management areas through simulation modelling and georesistivity imaging in rolling landscape. The study was carried out in Southern Italy, during 2 years of wheat monoculture; extensive soil properties and in-season plant measurements were measured. This study showed that soil water content was the main factor affecting spatial variation of yield for both years. The interactions between rainfall, topography and soil attributes increase the chances to observe yield variability among years. The principal component analysis demonstrated that for both years, soil water content explained most of the variability. The crop simulation model provided excellent results when compared with measured data with root mean square error of 0.2 t ha⁻¹. The simulated cumulative probability function showed that the model was able to confirm the yield temporal stability of three different zones.