Environmental and Economic Benefits of Saline-Sodic Soil Reclamation Using Low-quality Water and Soil Amendments in Conjunction with a Rice–Wheat Cropping System

A combination of appropriate crop rotation(s) and management interventions has the potential to transform saline‐sodic soil and water resources from an environmental burden into an economic asset. We carried out 2‐year field studies in the Indus Basin of Pakistan to evaluate different irrigation and soil management options of using saline‐sodic waters (SSW) and soils for reclamation and for growing salt‐tolerant cultivars of rice (SSRI‐8) and wheat (SIS‐32). These soils have variable levels of salinity and sodicity (EC_e 9–44 dS m^?1 and SAR 83–319). The treatments on both the sites were the same and consisted of: (1) Irrigation with SSW, (2) Irrigation with freshwater (FW), (3) Soil application of gypsum at 100 % gypsum requirement of soil + SSW (G + SSW), (4) G + one irrigation with SSW and one with FW (G + 1SSW + 1FW), (5) G + two irrigations with SSW and one with FW (G + 2SSW + 1FW), (6) Farm manure at 25 Mg ha^?1 each year before rice + one irrigation with SSW and one with FW (FM + 1SSW + 1FW) and (7) FM + two irrigations with SSW and one with FW (FM + 2SSW + 1FW). Rice was grown as the first crop. After harvesting final wheat crop (fourth in sequence), maximum decrease in bulk density and increase in infiltration rate was observed with G + 1SSW + 1FW while FM + 1SSW + 1FW treatment showed higher decrease in pH_s and EC_e. Significantly the highest decrease in SAR occurred at both sites with G + 1SSW + 1FW. Maximum yields of rice and wheat were generally observed with G + 1SSW + 1FW. The crop yield and economic benefits with treatments showed a positive correlation with that of improvement in soil physical and chemical properties. Overall, the greatest net benefit was obtained from G + 1SSW + 1FW treatment. We also found that the farmers’ management skills were crucial in the overall success in improving crop yields during reclamation of saline‐sodic soils. Based on the results of this study, we propose that SSW could be used to reclaim saline‐sodic soils by using a rice–wheat rotation and a site‐specific combination of soil amendments and water application strategies.     

Effectiveness of Sulphuric Acid and Gypsum for the Reclamation of a Calcareous Saline-Sodic Soil Under Four Crop Rotations

As a low‐cost strategy, the cultivation of certain salt‐tolerant crop species on calcareous saline‐sodic soils, i.e. phytoreclamation, has enjoyed great attention in recent years. A lysimeter study was carried out to evaluate whether a phytoreclamation approach alone, or in combination with some booster dose of either gypsum or sulphuric acid, is sufficient to reclaim a calcareous, moderately saline‐sodic soil. Four crop rotations, rice (Oryza sativa L.)–wheat (Triticum aestivum L.)–sesbania (Sesbania aculeata L.); rice–berseem (Trifolium alexandrinum L.); Kallar grass (Leptochloa fusca L.)–alfalfa (Medicago sativa L.) and sesbania–berseem were tested against three treatments: (T₁) control, (T₂) sulphuric acid application 25 % of soil gypsum requirement (SGR), and (T₃) application of gypsum 25 % SGR. To decrease the sodium adsorption ratio of the saline‐sodic soil well below the threshold level, especially from deeper depth, a booster dose of gypsum or sulphuric acid 25 % SGR was quite effective. Rice–berseem and Kallar grass–alfalfa rotations were more promising in combination with inorganic amendments than the rest of the rotations. The study also suggests that better yields of wheat and rice crops can be obtained with the application of inorganic amendments like gypsum or sulphuric acid. However, Kallar grass yield was somewhat suppressed with these amendments.     

Spatial variability and reclamation of salinity and sodicity in a Kenyan irrigation scheme

Salinity and sodicity of soils are two common problems encountered in the Hola Irrigation Scheme in east Kenya. Both result in poor crop performance and reduced yields. Based upon a detailed survey in a 405 ha area consisting of 45 irrigation blocks, the spatial variability of pH, EC_e and ESP was studied. Data obtained were analyzed using geostatistical procedures in a geographical information system. As it turned out, sodicity in the area has a clear spatial structure. Also differences in homogeneity per block were observed. Reclamation will be necessary, mainly because of the sodicity in the area, while salinity is still at an acceptable level for all crops grown and only small amounts of water are needed to maintain these EC levels. This results in varying gypsum requirements for reclamation for different blocks. A Geographical Information System (GIS) was used to handle large amounts of data and to compare the effects of different land use scenarios.     

Nitrogen Balance of Legume-Wheat Cropping Sequences

In a lysimeter trial the legumes faba bean ( Vicia faba ), red clover ( Trifolium repens ), and alfalfa ( Medicago sativa ) were grown for two years, followed by winter wheat on all plots in the third year. Plots fertilized with mineral nitrogen and a rye/maize – wheat cropping sequence were included for comparisons. These four cropping sequences were replicated twice in 1982–1984 and 1985–1987, respectively. Two soils, a loamy sand and a sandy loam were used.
On average of both soils:
– N fixation during two years was 461 kg N/ha, 803 kg N/ha, and 790 kg N/ha for faba bean, red clover, and alfalfa, respectively.
– Leaching of nitrogen occurred mainly during the periods of winter fallow or, in case of the perennial legumes, after incorporation of residues into the soil and planting of wheat. Average leaching for all 6 years was 49, 28, and 29 kg ha⁻¹ year⁻¹ for faba bean, red clover, and alfalfa, respectively.
– In the period of wheat growth and before planting the new crop (1.5 years) in 1984/85 51–64 kg N/ha and 1986/87 68–94 kg N/ha were leached after growing legumes. Leaching was less for rye/maize fertilized with mineral N, 41 kg N/ha in 1984/85, and 51 kg N/ha in 1986/87, respectively.
– Winter wheat grown after legumes took up 18 kg N/ha < 47 kg N/ha < 65 kg N/ha on average of both soils and 2 years (1984, 1987) after faba bean, red clover, and alfalfa, respectively. This indicates a nitrogen recovery of 24–44% of the legume N potentially available, and consequently a loss by leaching from 56 to 76 %.
On the sandy loam amount of drainage water and N leaching were lower, and faba bean and wheat yields higher than on the loamy sandy soil.     

秸秆还田与化肥配施对汉中盆地稻麦轮作农田土壤固碳及经济效益的影响

为汉中盆地秸秆还田技术和合理化肥减量技术提供科学依据,2015—2017年小麦和水稻生长季,设置秸秆不还田+常规施肥(SN+NPK);秸秆常规还田+常规施肥(S+NPK);秸秆促腐还田+常规施肥(SD+NPK);秸秆促腐还田+化肥减量15%(SD+85%NPK);秸秆促腐还田+化肥减量30%(SD+70%NPK),共5个处理,研究其对土壤总有机碳(TOC)、活性有机碳(LOC)、碳储量(SCS)、作物产量及经济效益的影响。结果表明与秸秆不还田配施常规施肥处理(SN+NPK)相比,秸秆还田配施不同比例化肥处理显著提高了稻田0～15cm土层的TOC和LOC,增幅分别为3.62%～25.07%和23.01%～46.79%; S+NPK和SD+NPK处理提高了0～30 cm碳储量,增幅分别为4.67%和18.20%。而SD+85%NPK和SD+70%NPK分别降低8.31%和9.83%。S+NPK和SD+NPK处理显著增加了小麦和水稻籽粒产量,而SD+85%NPK和SD+70%NPK处理均降低了小麦和水稻产量,周年产量2年平均增幅分别为3.47%、8.70%、-3.65%、-8.12%。与SN+NPK处理相比, S+NPK、SD+NPK、SD+85%NPK、SD+70%NPK处理周年经济效益2年平均增幅分别为16.91%、23.56%、6.02%、1.06%。土壤有机碳、作物产量和经济效益SD+NPK处理的最高, S+NPK处理次之,SD+70%NPK处理最低,与之相比,SD+85%NPK处理在小麦和水稻两季共减少化肥80kghm–2,作物周年产量降低不明显,经济效益略有增加。秸秆还田与常规化肥配施是提高汉中盆地稻麦轮作体系农田固碳、产量及经济效益的最佳措施,两季作物全量还田条件下化肥用量减少15%是适宜该区域的绿色生产模式。     

Chemical changes in a saline-sodic soil after gypsum application and cropping

Reclamation is needed on three million ha of slowly permeable saline-sodic soils in the Indus Plain of Pakistan. Previous studies measured an increased field-saturated hydraulic conductivity (K_fs) in the soil under study with cropping and gypsum application. This field experiment was conducted on a low permeability, saline-sodic soil (a fine-loamy, mixed thermic Typic Natrustalf) to compare the leaching of sodium and soluble salts and changes in chemical properties after various treatments. Treatments were: (i) perennial alfalfa (Madicago sativa L.), (ii) a rotation of sesbania [Sesbania bispinosa (Jacq.)W.F. Wright]-wheat (Triticum aestivum L.)-sesbania, (iii) incorporated wheat straw at 7.5 Mg ha⁻¹ and (iv) a fallow control. These four treatments were each combined with and without 25 Mg ha⁻¹ of gypsum and open-ditch drainage. Electrical conductivity (EC), pH, Na⁺, Ca²⁺, Mg²⁺ and Cl⁻ of the soil in the saturated paste extract under each treatment were measured in each 20 cm increment to 120 cm after 6 month and 1 yr. Gypsum application increased the soluble Na⁺ in the top 20 cm soil. Poor internal drainage of the soil caused the exchanged Na⁺ to remain in the soil solution. However, one year after the treatments, the crop rotation with gypsum significantly decreased SAR, EC, pH and Cl⁻ in the top 20 cm of soil. Alfalfa decreased these same parameters when compared to fallow in the top 80 cm of soil in gypsum-treated plots. The open-ditch drainage was not helpful in reclamation of this soil. In general, for surface soil improvement, a combination of added gypsum plus crop rotation was the best. For improvement of the deeper soil profile, gypsum plus alfalfa was the most effective of the treatments used.     

Yield potential and salt tolerance of quinoa on salt‐degraded soils of Pakistan

Quinoa is recently introduced to Pakistan as a salt‐tolerant crop of high nutritional value. Open field trials were conducted to evaluate its performance on normal and salinity/sodicity‐degraded lands at two locations of different salinity/sodicity levels, S₁ (UAF Farm, Normal Soil), S₂ (Paroka Farm UAF, saline sodic), S₃ (SSRI Farm, normal) and S₄ (SSRI Farm, saline sodic) during 2013–2014. Two genotypes (Q‐2 and Q‐7) were grown in lines and were allowed to grow till maturity under RCBD split‐plot arrangement. Maximum seed yield (3,062 kg/ha) was achieved by Q‐7 at normal field (S₁) soil which was statistically similar with yield of same genotype obtained from salt‐affected field S₂ (2,870 kg/ha). Furthermore, low yield was seen from both genotypes from both S₃ and S₄ as compared to S₁ and S₂. Q‐7 was best under all four conditions. Minimum yield was recorded from Q‐2 (1,587 kg/ha) at S₄. Q‐7 had higher SOD, proline, phenolic and K⁺ contents, and lower Na⁺ content in leaves as compared to Q‐2. High levels of antioxidants and K⁺/Na⁺ of Q‐7 helped to withstand salt stress and might be the cause of higher yields under both normal and salt‐affected soils. Seed quality (mineral and protein) did not decrease considerably under salt‐affected soils even improved seed K⁺, Mg²⁺ and Mn²⁺.     

不同时期施用土壤改良剂对河灌区苏打盐碱地土壤及青贮玉米生长的影响

为明确盐碱地改良剂不同时期施用对河灌区盐碱地土壤的改良效果以及对青贮玉米生长的影响,采用田间试验方法,以青贮玉米‘瑞德2号’为供试作物,研究了河灌区重度苏打盐碱地国产DS、脱硫石膏、脱硫石膏配合DS 3种改良剂的秋季施用和春季施用对青贮玉米出苗率和鲜草产量的影响,分析了土壤(0~20 cm)pH、EC和碱化度的变化。结果表明：与对照（不施用改良剂）相比,施用改良剂处理的青贮玉米出苗率提高6.8%~72.7%,鲜草产量增加1223.2~28144.8 kg/hm2;土壤pH下降0.09~0.83,EC增加0.13~1.26 mS/cm,碱化度降低1.6%~19.8%;秋施和春施脱硫石膏、脱硫石膏配合DS均显著提高了青贮玉米的出苗率与鲜草产量。由此得出,3种盐碱地改良剂秋季施用效果均优于春季施用,其中以脱硫石膏配合DS的秋季施用效果最好。     

Quantifying rice yield gaps and their causes in Eastern and Southern Africa

The demand for rice in Eastern and Southern Africa is rapidly increasing because of changes in consumer preferences and urbanization. However, local rice production lags behind consumption, mainly due to low yield levels. In order to set priorities for research and development aimed at improving rice productivity, there is a need to characterize the rice production environments, to quantify rice yield gaps—that is, the difference between average on-farm yield and the best farmers’ yield—and to identify causes of yield gaps. Such information will help identifying and targeting technologies to alleviate the main constraints, and consequently to reduce existing yield gaps. Yield gap surveys were conducted on 357 rice farms at eight sites (19–50 farmers per site) across five rice-producing countries in Eastern and Southern Africa—that is Ethiopia, Madagascar, Rwanda, Tanzania and Uganda—for one or two years (2012–13) to collect both quantitative and qualitative data at field and farm level. Average farm yields measured at the eight sites ranged from 1.8 to 4.3 t/ha and the average yield gap ranged from 0.8 to 3.4 t/ha. Across rice-growing environments, major causes for yield variability were straw management, weeding frequency, growth duration of the variety, weed cover, fertilizer (mineral and organic) application frequency, levelling and iron toxicity. Land levelling increased the yield by 0.74 t/ha, bird control increased the yield by 1.44 t/ha, and sub-optimal management of weeds reduced the yield by 3.6 to 4.4 t/ha. There is great potential to reduce the current rice yield gap in ESA, by focusing on improvements of those crop management practices that address the main site-specific causes for sub-optimal yields.     

长期定位施肥对土壤有机质、不同形态氮含量及作物产量的影响

通过长期定位试验,研究不同施肥处理对河北省低平原区土壤有机质、不同氮形态含量及作物产量的影响,旨在为该区冬小麦–夏玉米轮作系统秸秆全量还田下土壤肥力和作物产量的提高提供理论依据。结果表明,经过36个小麦玉米轮作周期的不同施肥处理后,与不施肥处理（CK）相比,施肥可以提高土壤有机质和全氮含量,且随化肥施用量的增加而逐渐增加。在化肥施用量≤N 360kg/hm²+P₂O₅ 240kg/hm²时,秸秆还田较不还田可显著提高土壤有机质和全氮含量,在化肥施用量为N 540kg/hm²+P₂O₅ 360kg/hm²时,增加速度减缓。与CK相比,长期施肥提高了土壤碱解氮和硝态氮含量,而对土壤铵态氮含量没有显著影响。单施化肥时,表层土壤碱解氮和硝态氮含量随氮肥施用量的增加而增加;在秸秆还田下,N360+P240+S9000处理表层土壤碱解氮和硝态氮含量最高。施肥显著提高了作物产量,单施化肥处理,小麦、玉米产量均随施肥量的增加而逐渐增加;秸秆还田条件下,小麦产量在化肥施用量≤N 360kg/hm²+P₂O₅ 240kg/hm²时较单独施用化肥的处理增产。由以上结果可知,长期施肥可提高土壤肥力,增加土壤有机质和全氮含量,适宜的氮肥施用量配合秸秆还田可固持土壤有机碳和全氮,过量氮肥不利于土壤有机质的累积。长期单施化肥或化肥配合秸秆还田均可提高土壤碱解氮和硝态氮含量,对土壤铵态氮含量无显著影响。长期施肥可提高作物产量,在秸秆还田条件下,化肥施用量为N 360kg/hm²+P₂O₅ 240kg/hm²时,增产效果较好。     

盐碱土壤上石膏与有机物料组合对作物产量与籽粒养分含量的影响

为了研究不同改良物料（脱硫石膏、草碳、腐殖酸）单一施用与不同配比在盐碱土壤上对作物产量与土壤理化性质的短期改良效果,于2014—2015 年在山东乐陵地区进行了8 处理3 重复的随机区组试验。结果表明：第一季小麦相比未改良处理,脱硫石膏、有机物料单一施用及不同配比均没有显著增加小麦产量。玉米季时,脱硫石膏与腐殖酸单一施用与其1:2 组合与未改良处理在玉米产量上没有显著性差异,但脱硫石膏与腐殖酸1:1 组合实现玉米增产40%。改良物料1:1 组合措施显著提高了玉米籽粒的氮与钾浓度,同时降低土壤pH 0.5 个单位。土壤中的速效钾含量显著提高,交换性钠的含量显著降低,维持了土壤溶液中钾钠比的平衡。因此,盐碱土短期的改良过程中,脱硫石膏与腐殖酸1:1 组合施用,对于改良土壤盐碱具有一定的应用前景。     

N-Dynamik des Bodens, Ertragsbildung und Stickstoffentzug von Winterweizen bei unterschiedlicher Höhe und Verteilung der mineralischen N-Düngung

NO₃ dynamics in the soil, yield formation and N uptake of winter wheat as influenced by dosage and distribution effects of N-fertilizer application
In a 4 year series of field trials carried out with 9 regimes of nitrogen fertilizer application at two trial sites with rather shallow top soil layers but large deviations in soil characteristics, grain yield varied between 50 dt/ ha and 120 dt/ha with nitrogen doses from 0–170 kg N/ha. Soil nitrogen supply for wheat grain formation on unfertilized plots reached 80 kg N/ha/year within the narrow range of 75–95 kg N/ha in different years at both sites which amounts to 1.5 % and 0.5 % of the highly different N-content of the trial sites.
The most successful nitrogen application regimes are characterized by modest fertilizer doses in early spring and the delay of supplemental fertilizer doses until growth stage EC 32. They resulted into modest NO) soil content from EC 29 to EC 32 and/or a noticable decrease of soil NO₃ content during growth stage EC 30–32, which seems to be responsible for the development of only modest stand densities and reduced straw yield, while the delayed supplementation with nitrogen fertilizer overcompensated these effects mainly by increased grain numbers/ear and a remarkable improvement of harvest index.
The contribution of soil borne nitrogen to kernel yield formation started to decrease with even low dosages of supplemental nitrogen fertilization with the exception of the highest yielding season 1987/88. Top levels of grain yield have been regularly obtained with supplemental nitrogen fertilizer dosages about 40 kg N/ha below grain yield nitrogen extraction if they were added within favorable application regimes.     

Effect of Azolla as an Organic Source of Nitrogen in Rice-Wheat Cropping System

Increasing area under high yielding varieties require more quantity of fertilizers and other inputs for higher yield. However, utilization of available biomass could reduce the dependence on costly crop production inputs like fertilizers. In light of this, field experiments were carried out at Agricultural Engineering Department, Indian Institute of Technology, Kharagpur for two years i.e. 1982–83 and 1983–84 to find out the possibilities to meet at least a part of nitrogen requirement through incorporation of Azolla in rice-wheat cropping system. Incorporation of 10 t/ha of fresh Azolla before planting + 30 kg N/ha through fertilizer as basal proved to be the best and recorded maximum land productivity in rice-wheat cropping system. This treatment recorded 117.69 and 103.30 per cent higher grain yield of rice and wheat respectively over control. About 30 kg N could be supplemented through preplanting incorporation of 5 t fresh Azolla. The result indicated that Azolla could be utilized as an alternative source of N-fertilizer for higher production of crops in rice-wheat cropping system.     

Soil sodicity is more detrimental than salinity for quinoa (Chenopodium quinoa Willd.): A multivariate comparison of physiological,biochemical and nutritional quality attributes

Soil salinization is a serious environmental problem worldwide. To explore the comparative effects of soil salinity and sodicity on physiological, biochemical and nutritional quality attributes of four quinoa genotypes (A1, A7, Puno, Vikinga), pot and field experiments were performed on non‐saline soil and two types of salt‐affected soils designated as SS1 (saline) and SS2 (saline‐sodic). The results of both the experiments showed similar reduction pattern in biomass (11%–44%), chlorophyll content (10%–36%), stomatal conductance (18%–32%) and grain yield (30%–47%) of four genotypes on SS2 compared with SS1. Higher sodicity level of SS2 resulted in more Na accumulation (23%–40%) and oxidative damage (12%–35% decrease in membrane stability) leading to an increase in the activities of antioxidant enzymes (SOD, POD, CAT) in all the genotypes. Grain mineral contents (except Na and Mg) were decreased more in SS2 than SS1. Multivariate analysis revealed that grain Na content has negative correlation with all the nutritional quality attributes except Mg and fibre contents. Genotypes A1 and A7 were more salt tolerant with better grain nutritional quality than Puno and Vikinga. It is concluded that soil sodicity is more detrimental than salinity, and quinoa genotypes A1 and A7 are better than Puno and Vikinga for cultivation on saline and saline‐sodic soils.     

生物炭对设施栽培土壤重金属Cd形态变化的影响

设施土壤重金属Cd污染问题备受关注,为阐明生物炭对设施栽培土壤重金属Cd污染的修复效果,试验设置B0(0 t/公顷)、B10(10t/公顷)和B20(20t/公顷)3个生物炭水平,研究生物炭增施对土壤Cd形态、含量以及生物有效性的影响。结果表明：生物炭施用显著增加设施土壤pH值和有机质含量,改变了土壤Cd的形态分布,氧化态、有机态和残渣态含量增加,交换态Cd含量降低。随着生物炭施用量的增加,土壤固定Cd的速率会增加。与对照相比,B10降低土壤交换态Cd 45-62％,而B20可降低66-89％。另外,试验还表明,生物炭对Cd污染较轻的设施大棚土壤有效态Cd的固定效果要好于Cd污染严重的设施大棚。因此,生物炭可以通过改变设施土壤Cd形态,降低土壤重金属有效性,但对受Cd污染严重的设施土壤的修复效果不好。     

Long-term effective microorganisms application promote growth and increase yields and nutrition of wheat in China

An eleven years long-term field experiment for soil fertility and crop yield improvement had been conducted at China Agricultural University's Qu-Zhou experiment station since 1993. The field experiment included three treatments: effective microorganisms (EM) compost treatment; traditional compost treatment; and unfertilized control. The results revealed that long-term application of EM compost gave the highest values for the measured parameters and the lowest values in the control plot. The application of EM in combination with compost significantly increased wheat straw biomass, grain yields, straw and grain nutrition compared with traditional compost and control treatment. Wheat straw biomass, grain yields, straw and grain nutrition were significantly higher in compost soils than in untreated soil. This study indicated that application of EM significantly increased the efficiency of organic nutrient sources.     

The Effects of Prolonged Drought and Nitrogen Fertilizer on Root and Shoot Growth and Water Uptake by Winter Wheat

Winter wheat growing on a silty clay loam soil was protected from rainfall by a mobile shelter for 100 days from tillering to maturity. During this time the crop was either irrigated according to demand or grew on stored soil water. The effects of this high and low water supply, in combination with a high and low N supply, on root and shoot growth and water uptake were studied.
The crop given both N and water yielded 9.7 t/ha of grain (85 % DM), drought reduced this to 7.9 t/ha, low N to 4.3 t/ha and drought and low N to 3.8 t/ha. Yield reductions were mainly due to fewer grains being produced.
Little root growth occurred in the topsoil during the drought but there was compensatory growth in the subsoil provided that N fertilizer was given. The droughted crops rooted to 160 cm, about 20 cm deeper than the irrigated crops, but the amount of root in the deep subsoil was very small, less than 0.1 cm/cm³ ai 140–160 cm, compared with 5–9 cm/cm³ in the topsoil.
The crop demand for water at any given time was partitioned throughout the root system but atmospheric demand was only met whilst the topsoil was wet. The fertilized, droughted crop extracted all of the potentially available water to a depth of 80 cm and a mean rooting density of 1 cm/cm³ was necessary to achieve this. Uptake from below this depth was limited by root growth.
The limiting value of the potential soil water deficit was 170 mm, and weather records showed that this would be exceeded one year in ten, on average. The likelihood of yield reduction due to drought could be reduced on this soil by improving root growth below 80 cm depth, although the chances of achieving this are low as root growth was probably limited by poor soil structure.     

Die Ertragsentwicklung von Wintergetreide und Zuckerrüben bei dauerhafter Senkung des N-Düngungsniveaus

Effects of Long-term Fertilizer N Reduction on Winter Grain and Sugar Beet Yields
The results of recent field experiments concerning the effect of long-term N-reduction on the yield and quality of sugar beet, winter wheat and winter barley on plots which had previously had received ample amounts of N are studied in this paper.
The yield and quality of crops harvested on plots where N-dressings had been reduced for 6–8 years were similar to those of crops grown on plots where N-application had been reduced for only 1 year. Grain yield of winter wheat and winter barley grown without any N-application decreased to about 60 % of amounts normally harvested under local conditions with recommended N dressings, whereas the white sugar yield still remained at 90 %. The yields decreased slightly with an increase in the duration of the experiments. Yields of both cereals and beets remained constant within each level of fertilization, even 6 years after inition of trials with 50, 75 and 125 % of locally recommended N dressings.
On plots that did not receive nitrogen fertilization, N-contents of grain were between 1.5 and 1.7 % for winter wheat and 1.0 and 1.6 % N for winter barley. These contents remained constant over a trial period of 6 years. The amount of annual export of 55–91 kg N/ha also remained constant. Limited N availability causes a decrease in grain protein content rather than in grain yield.
Compared to winter grain species, sugar beet (with 74–117 kg N/ha in the beet body) could realize the highest annual export of nitrogen from the plot. Differences in annual N export existing between the various locations of the plots cannot be explained by differences in soil quality. Continuous high yields that were found even without any N-dressings may be explained by asymbiotic N-fixation, deposition of atmospheric N and a progressive decrease in soil N with 17–56 kg N/ha removed from soil resources annually.     

晋南石灰性土壤钾素变化及小麦施钾效果

晋南石灰性土壤钾素动态研究表明：潮土、褐土土壤速效钾含量均呈下降趋势，其中潮土下降３１．２５ｍｇ／ｋｇ，褐土下降１５．７５ｍｇ／ｋｇ。土壤质地类型、农业生态区及种植制度不同，土壤速效钾含量下降不同。小麦钾肥试验结果表明：亩施Ｋ２ＳＯ４５～２０ｋｇ，产量增加５２．９～１１１．５ｋｇ／亩，净增收益３２．７～６２．６元／亩。同时获得了小麦最高产量施肥量和经济最佳施肥量     

水稻秸秆生物炭对江汉平原麦区小麦养分吸收和产量的影响

旨在探明水稻秸秆生物炭施用量和施用时期对江汉平原稻茬麦养分吸收、土壤养分含量以及产量的影响。选择江汉平原典型潮土稻麦轮作区,以基施化肥但不施生物炭处理为对照,设置小麦播种前基施、返青拔节期追施以及两个时期同施不同剂量的生物炭等处理,采用比色法和火焰光度计法测定了不同处理小麦籽粒、植株茎叶和土壤的氮、磷、钾含量,并比较了籽粒产量的变化。结果表明,施用生物炭促进了小麦籽粒和植株茎叶对氮、磷、钾元素的吸收,增加了地上部分氮、磷、钾养分吸收总积累量,且以基施及追施13500 kg/hm²生物炭处理最高,较对照处理籽粒总氮、磷、钾分别提高了20.3%、17.8%和12.4%,茎叶总氮、磷、钾分别提高了11.9%、34.5%和13.9%,氮、磷、钾总积累量显著增加18.2%、24.0%、13.7%(P<0.05);施用生物炭后土壤pH升高、有机质和速效磷含量增加,小麦株高增高,结实率和千粒重增大。施用水稻秸秆生物炭对于改善土壤和提高小麦产量具有一定促进作用。