Organic fertilizer effects on growth,crop yield,and soil microbial biomass indices in sole and intercropped peas and oats under organic farming conditions

In a field experiment, peas (Pisum sativum L.) and oats (Avena sativa L.) were grown as sole crops and intercrops, fertilized with horse manure and yard-waste compost derived from shrub and garden cuttings at 10 t C ha⁻¹ each. The objectives were to compare the effects of these organic fertilizer and cropping system in organic farming on (a) yield of peas and oats, grown as the sole crop or intercropped, as well as N₂ fixation and photosynthetic rates, (b) the yield of wheat as a succeeding crop, (c) microbial biomass indices in soil and roots, and (d) microbial activity estimated by the CO₂ evolution rate in the field and the amount of organic fertilizers, recovered as particulate organic matter (POM). In general, organic fertilizer application improved nodule dry weight (DW), photosynthetic rates, N₂ fixation, and N accumulation of peas as well as N concentration in oat grain. Averaged across fertilizer treatments, pea/oat intercropping significantly decreased nodule DW, N₂ fixation and photosynthetic rate of peas by 14, 17, and 12%, respectively, and significantly increased the photosynthetic rate of oats by 20%. However, the land equivalent ratio (LER) of intercropped peas and oats exceeded 1.0, indicating a yield advantage over sole cropping. Soil microbial biomass was positively correlated with pea dry matter yields both in sole and intercropped systems. Organic fertilizers increased the contents of microbial biomass C, N, P, and fungal ergosterol in soil and CO₂ production, whereas the cropping system had no effects on these microbial indices. According to the organic fertilizer recovered as POM, 70% (manure) and 64% (compost) of added C were decomposed, but only 39% (manure) and 13% (compost) could be attributed to CO₂–C during a 101-day period. This indicated that horse manure was more readily available to soil microorganisms than compost, leading to increased grain yields of the succeeding winter wheat.     

不同施肥对土壤微生物活性、群落结构和生物量的影响

本文概述了不同施肥措施对微生物活性、生物量和群落结构的影响,以及微生物因原有土壤肥力、施肥时间长短、肥料数量等不同而对不同施肥措施做出不同的响应。施肥是影响土壤碳、氮含量的最主要农业措施,而土壤中的碳和氮是微生物生命活动的基础,土壤微生物生命活动是土壤养分转化的活的驱动力。化肥对微生物数量、活性和多样性的直接影响很有限,但它可通过增加作物产量、秸秆还田量和土壤有机质的方式间接增加微生物活性。化肥尤其氮肥的另外一个间接作用就是使土壤酸化,从而对微生物有显著负影响。而有机肥可直接为土壤微生物提供碳源,或通过促作物生长和秸秆还田为微生物间接提供碳源。总之,长期不同施肥改变土壤养分的转化途径,从而影响土壤供氮能力和碳贮备能力,最终影响土壤可持续性和土壤质量。     

有机肥替代对棉花养分积累、产量及土壤肥力的影响

【目的】研究不同有机肥替代率对黄河流域棉株生物量、养分积累、产量、氮磷比及土壤肥力的影响,试图探索出有机肥替代化肥的适宜替代率,为有机肥、无机肥在黄河流域棉田合理施用提供参考依据。【方法】试验始于2016年,在中国农业科学院棉花研究所试验基地设置6个施肥处理:T1:不施肥,T2:100%化肥,T3:20%有机肥+80%化肥,T4:40%有机肥+60%化肥,T5:50%有机肥+50%化肥,T6:100%有机肥。经3年施肥后,2018年进行田间取样,分析不同施肥处理对棉花生物量、养分积累、产量、氮磷比及土壤肥力的影响。【结果】(1)有机肥替代50%化肥处理提高棉株生物量、养分积累和籽棉产量。(2)与单施化肥处理相比,施用有机肥处理土壤有机质、全氮、速效磷、碱解氮含量均有增高趋势,全部施有机肥显著增加土壤速效磷含量。(3)棉株全氮、全磷积累量与棉株生物量呈极显著正相关,棉株根、茎氮磷比与籽棉产量呈极显著负相关。【结论】有机肥替代部分化肥能减少化肥用量,连续应用有机肥替代部分化肥具有增加土壤肥力的趋势;有机肥替代50%化肥处理能增加棉花生物量、养分积累量,提高籽棉产量,替代效果最好。     

Sugar beet rotation effects on soil organic matter and calculated humus balance in Central Germany

In order to quantify the influence of land use systems on the level of soil organic matter (SOM) to develop recommendations, long-term field studies are essential. Based on a crop rotation experiment which commenced in 1970, this paper investigated the impact of crop rotations involving increased proportions of sugar beet on SOM content. To this end, soil samples were taken in 2010 and 2012 from the following crop rotation sequences: sugar beet–sugar beet–winter wheat–winter wheat (SB–SB–WW–WW = 50%), sugar beet–sugar beet–sugar beet–winter wheat (SB–SB–SB–WW = 75%), sugar beet–grain maize (SB–GM = 50%) and sugar beet-monoculture (SB = 100%); these were analysed in terms of total organic carbon (TOC) and microbial biomass carbon (MBC) content, MBC/TOC ratio and the TOC stocks per hectare. In addition, humus balances were created (using the software REPRO, reference period 12 years) in order to calculate how well the soil was supplied with organic matter. In the field experiment, harvest by-products (WW and GM straw as well as SB leaves) were removed. After 41 years, no statistically significant differences were measured between the crop rotations for the parameters TOC, MBC, MBC/TOC ratio and the TOC stock per hectare. However, the calculated humus balance was significantly affected by the crop rotation. The calculated humus balance became increasingly negative in the order SB–SB–WW–WW, SB–SB–SB–WW, SB monoculture and SB–GM, and correlated with the soil parameters. The calculated humus balances for the reference period did not reflect the actual demand for organic matter by the crop rotations, but instead overestimated it.     

富有机质土壤栽培方式对大白菜产量及品质的影响

以田园土壤栽培为对照,研究了以农业废弃物腐熟麦秸与腐熟大粪干及洁净土壤等为主要原料配置而成的富有机质土壤限根和非限根栽培对大白菜产量和品质的影响。结果表明,富有机质土壤非限根栽培的大白菜生长势好,根系活力强,叶绿素含量高,增产效果显著,产量较对照提高了20.68%;亚硝酸盐未检出,硝酸盐含量降低了359mg/kg,降幅达38.26%,富有机质土壤非限根栽培还明显增加了大白菜叶球的干物质含量,增幅为17.2 %;与对照相比, 富有机质土壤非限根栽培的大白菜的粗蛋白含量、总糖含量和维生素C含量分别提高了4.9%、0.9 %和2.44 %。表明富有机质土壤非限根栽培方式对提高白菜产量及改善营养品质效果良好。     

不同降水年型下水氮调控对小麦产量及生物量的影响

水和氮是影响西北黄土高原雨养农业区粮食生产的主要因素,但其增产效应受降水年型影响明显。本水氮调控试验利用APSIM模型在甘肃省定西市安定区1971—2018年气象数据,分析了不同降水年型下水氮管理对小麦产量和生物量的变异系数、可持续性指数的影响,明确了各年型产量与施氮量、降水量之间的关系。结果表明,模型模拟的小麦产量和生物量的决定系数R2均在0.90以上,一致性指标D均在0.95以上,归一化均方根误差(NRMSE)均在15%以下,表明该模型在研究区具有较好的模型拟合度和适应性。通过二元二次回归方程探讨了其最优产量下的水氮优化组合,在当年年降水总量的基础上,干旱年小麦达潜在最优产量时(3492.6kghm–2),降水需增加39.73%,应施氮182.73 kg hm–2;平水年小麦达潜在最优产量时(4514.5 kg hm–2),降水需增加45.26%,应施氮208.26 kg hm–2;湿润年小麦达潜在最优产量时(4890.3 kg hm–2),降水需增加46.31%,应施氮211.15 kg hm–2。研究结果可为研究区不同降水年型下缓解小麦干旱和养分胁迫,节约化肥资源和农业可持续性发展提供理论依据。     

Effect of depth of fertilizer banded-placement on growth,nutrient uptake and yield of oilseed rape (Brassica napus L.)

A better understanding of crop growth and nutrient uptake responses to the depth of fertilizer banded-placement in the soil is needed if growth and nutrient uptake responses are to be maximized. A two-year field study covering two rape seasons (2010–2011 and 2011–2012) was conducted to examine the effect of banded-placement of N–P–K fertilizer at various depths on growth, nutrient uptake and yield of oilseed rape (Brassica napus L.). The results showed that fertilization at 10 cm and 15 cm soil depth produced greater taproot length and dry weight than fertilization at 0 cm and 5 cm. 0 cm and 5 cm deep fertilization significantly increased the lateral root distribution at 0–5 cm soil depth, while 10 cm and 15 cm deep fertilization induced more lateral root proliferation at 5–15 cm soil depth. At 36 days after sowing (DAS), 5 cm deep fertilization produced better aboveground growth and nutrient uptake than 10 cm and 15 cm deep fertilization. However, reversed results were observed after 36 DAS. 10 cm and 15 cm deep fertilization produced more rapeseed than 0 cm and 5 cm deep fertilization, moreover, the yield difference was more significant in drought season (2010–2011) than in relatively normal season (2011–2012). In summary, these results preliminarily suggest that both 10 cm and 15 cm are relatively proper fertilizer placement depth when the practice of banding fertilizer is used in oilseed rape production. But from the viewpoint of diminishing the production cost, 10 cm deep fertilization should be recommended in actual farming. Because 15 cm deep fertilization may require higher mechanical power input, and thus resulting in higher cost of production.     

模拟氮沉降和刈割对内蒙古典型草原土壤微生物量的影响

为探讨大气氮沉降对草原土壤微生物量的影响,采用模拟大气氮沉降的方法对试验小区进行施N处理,研究了不同施N水平下刈割对土壤微生物量C、N的影响。结果表明：不同施N水平对土壤微生物量C、N没有显著影响,但是有增加土壤微生物量C、N的趋势;在刈割和施N的交互作用下降低了土壤中微生物量C、N的含量。不同施N水平能降低草原植被根系生物量、促进土壤酸化。施N量为20g N?m-2?a-1时对土壤微生物量C、N的抑制性最强。     

滨海盐碱地棉花秸秆还田和深松对棉花干物质积累、养分吸收及产量的影响

以鲁棉研36号为试验材料,在滨海盐碱地设置常规耕作(CT)、深松(ST)、秸秆还田(SR)、秸秆还田+深松(SRT)4个处理,研究棉花秸秆还田和深松对棉花产量、0～40 cm土层含盐量、棉花干物质积累动态、氮(N)磷(P)钾(K)养分积累和分配特性的影响。结果表明,秸秆还田在2年试验内均可增加棉花产量, SR产量比CT增加33.9%, SRT比ST增加32.1%;深松在2017年增加了棉花产量, 2018年对产量无影响。秸秆还田在2年试验中均降低0～40 cm土层含盐量, SR的含盐量在棉花生育后期比CT降低22.4%, SRT的土壤含盐量比ST降低20.7%;深松在2年试验内对20～40cm土层含盐量的影响不一致,ST含盐量在2017年棉花生育后期比CT降低16.5%,但在2018年深松对土壤含盐量无影响。棉花干物质和N、P、K积累动态均符合Logistic生长曲线。棉花秸秆还田后增加了棉花干物质和N、P、K的最大积累量, SR的干物质、N、P、K最大积累量比CT分别提高35.5%、38.3%、53.4%和55.0%, SRT比ST分别提高27.0%、30.7%、21.2%和42.4...     

Short time effects of biological and inter-row subsoiling on yield of potatoes grown on a loamy sand,and on soil penetration resistance,root growth and nitrogen uptake

Soil compaction, especially subsoil compaction, in agricultural fields has increased due to widespread use of heavy machines and intensification of vehicular traffic. Subsoil compaction changes the relative distribution of roots between soil layers and may restrict root development to the upper part of the soil profile, limiting water and mineral availability. This study investigated the direct effects of inter-row subsoiling, biological subsoiling and a combination of these two methods on soil penetration resistance, root length density, nitrogen uptake and yield. In field experiments with potatoes in 2013 and 2014, inter-row subsoiling (subsoiler) and biological subsoiling (preceding crops) were studied as two potential methods to reduce soil penetration resistance. Inter-row subsoiling was carried out post planting and the preceding crops were established one year, or in one case two years, prior to planting. Soil resistance was determined with a penetrometer three weeks after the potatoes were planted and root length density was measured after soil core sampling 2 months after emergence. Nitrogen uptake was determined in haulm (at haulm killing) and tubers (at harvest). Inter-row subsoiling had the greatest effect on soil penetration resistance, whereas biological subsoiling showed no effects. Root length density (RDL) in the combined treatment was higher than in the separate inter-row and biological subsoiling treatments and the control, whereas for the separate inter-row and biological subsoiling treatments, RLD was higher than in the control. Nitrogen uptake increased with inter-row subsoiling and was significantly higher than in the biological subsoiling and control treatments. However, in these experiments with a good supply of nutrients and water, no yield differences between any treatments were observed.     

Genetic effects on biomass yield in interspecific hybrids between Brassica napus and B. rapa

This study was conducted to estimate the genetic effects on biomass yield in the interspecific hybrids between Brassica napus and B. rapa, and to evaluate the relationship between parental genetic diversity and its effect on biomass yield of interspecific hybrids. Six cultivars and lines of oilseed B. napus and 20 cultivars of oilseed B. rapa from different regions of the world were chosen to produce interspecific hybrids using NC design II. Obvious genetic differences between B. rapa and B. napus were detected by RFLP. In addition, Chinese B. rapa and European B. rapa were shown genetically differences. Plant biomass yield from these interspecific hybrids were measured at the end of flowering period. Significant differences were detected among general combining ability (GCA) effects over two years and specific combining ability (SCA) effects differences were detected in 2000. The ratios of mean squares, (σ² _GCA(f) + σ² _GCA(m)) / (σ² _GCA(f) + σ² _GCA(m) + σ² _SCA), were 89% and 88% in 1999 and 2000, respectively. This indicates that both additive effects and non-additive effects contributed to the biomass yield of interspecific hybrids and the former played more important role. Some European B. rapa had significant negative GCA effects while many of Chinese B. rapa had significant positive GCA effects, indicating that Chinese B. rapa may be a valuable source for transferring favorable genes of biomass yield to B. napus. Significant positive correlation between parental genetic distance and biomass yield of interspecific hybrids implies that larger genetic distance results in higher biomass yield for the interspecific hybrids. A way to utilize interspecific heterosis for seed yield was discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

有机培肥与轮耕方式对夏玉米田土壤碳氮和产量的影响

探明不同轮耕和有机培肥方式对夏玉米田土壤碳氮及其酶活性的影响,对提升农田土壤肥力及促进玉米高产具有重要意义。设秸秆(P)与牛粪(F)两种有机培肥方式和小麦季旋耕-玉米季深松(RS)、小麦季深松-玉米季免耕(SN)、小麦季翻耕-玉米季免耕(CN) 3种轮耕方式,共6个处理,于2015—2016和2016—2017玉米收获期采样测定,研究了不同有机培肥和轮耕方式对土壤碳氮及其酶活性和作物产量的影响。结果表明,轮耕方式、有机肥及其交互效应对土壤肥力有显著影响。在0～10 cm和10～20 cm土层,与轮耕方式CN相比, RS和SN能够显著提高土壤有机碳、全氮含量和脲酶、蔗糖酶活性。在轮耕方式RS中,与施用牛粪相比,秸秆还田显著提高了10～20 cm、20～30 cm和30～40 cm土层的有机碳含量,增加了10～20 cm土层的全氮含量和蔗糖酶活性。在轮耕方式SN中,与秸秆还田相比,施用牛粪显著提高了0～10 cm和10～20 cm土层的有机碳、全氮含量和蔗糖酶活性,增加了各土层脲酶活性。与秸秆还田+翻耕-免耕(PCN)相比,秸秆还田+旋耕-深松(PRS)和施用牛粪+深松-免耕(FSN)能显著提高土壤肥力。在0～10 cm和10～20 cm土层,各处理中以FSN增加土壤有机碳、全氮含量和蔗糖酶、脲酶活性最为明显。轮耕方式、有机肥及其交互效应对产量有显著影响。轮耕方式RS和SN的产量较CN分别显著提高了1.89%～10.49%、5.44%～11.99%。在轮耕方式RS中,产量表现为秸秆还田较施用牛粪显著提高了2.91%～3.11%;而在轮耕方式SN中,则表现为秸秆还田较施用牛粪显著降低了5.02%～9.07%。两年玉米产量均表现为FSNPRSFRSPSNFCNPCN。综上所述,在6种处理中,处理FSN在提高土壤肥力和产量方面最为显著,可以作为试验及周边地区适宜的轮耕培肥方式。     

Tillage and compaction effects on soil properties,root growth and yield of wheat during drought in a semi-arid environment

The calcareous sandy loam soils of Upper Eyre Peninsula in South Australia exhibit high penetrometer resistance throughout the growing season in soils which rarely wet to field capacity. In this area, tillage is normally limited to the top 0.05 m of soil.During two drought years, 1987 and 1988, experiments were carried out with deeper tillage in an attempt to ameliorate a perceived soil compaction problem at two sites (Minnipa and Cungena). At one of the sites a further series of experiments was conducted in which replicas of the tillage experiments were recompacted by four passes of a large (11,800 kg) tractor before seeding.Deeper tillage with a chisel plough at Minnipa had no measurable effect on water use or root growth in the period of measurement, or on grain yield. Soil strength was reduced by tillage to 0.3 m, but tillage to 0.15 m did not remove a hard pan below normal tillage depth. The loosening effect of deeper tillage was not measurable in dry soils by anthesis.Deeper tillage at Cungena resulted in some enhancement of root growth and water extraction. Grain yields were increased by tillage to 0.3 m in both seasons. Soil strength was considerably reduced by deeper tillage.Differences which occurred in the tillage experiments in water extraction, rooting density and grain yields did not occur in the recompaction experiments, but recompaction reduced the soil strength differences induced by deeper tillage. Yields were similar in the tillage and recompaction experiments in 1987, but in 1988 the recompacted deeper tilled treatments tended to yield less than the corresponding treatments in the tillage experiment. Bulk density was reduced by deeper tillage and increased by recompaction, but densities were generally not excessive, despite high penetrometer resistance.     

Effects of biogas digestion of clover/grass-leys, cover crops and crop residues on nitrogen cycle and crop yield in organic stockless farming systems

The trend towards specialization in conventional farming led to large agricultural areas in Germany and in Europe lacking livestock. Also stockless organic farming has increased during recent years. In organic farming clover/grass-ley (CG) provides nitrogen (N) to the whole cropping system via symbiotic N₂ fixation and also controls certain weeds. A common practice in organic farming, when ruminants are not present, is to leave the biomass from CG in the field for their residual fertility effect. CG biomass, crop residues (CR) and cover crops (CC) represent a large unexploited energy potential. It could be used by anaerobic digestion to produce biogas. A field experiment was carried out by implementing a whole cropping system with a typical crop rotation for such farming systems on the research station Gladbacherhof from 2002 to 2005. The crop rotation consisted of six crops (two legumes and four non-legume crops). The aim was to evaluate whether the use of N could be improved by processing biomass from CG, CR and CC in a biogas digester and using the effluents as a fertilizer, compared to common practice. In the control treatment, represented by the usual stockless system, the CG, CR and CC biomass were left on the ground for green manure purposes. In the biogas systems these substrates were harvested for digestion in a biogas plant. The effluents of digestion were used to manure the non-legumes in the same crop rotation. Results indicate that digestion of CG, CR and CC can increase the crop dry matter and N yields and the N content of wheat grains in organic stockless systems. Harvesting and digestion of residues and their reallocation after digestion resulted in a better and more even allocation of N within the whole crop rotation, in a higher N input via N₂ fixation and lower N losses due to emissions and probably in a higher N availability of digested manures in comparison to the same amounts of undigested biomass.     

荒漠绿洲不同种植方式对青贮玉米产量及水肥利用效率的影响

合理的种植方式可以在不增加灌溉耗水量的前提下,利用植物个体间的正相互作用关系和群体适应特点来达到提高作物产量和水分利用效率的目的。通过田间试验,研究了河西走廊黑河中游边缘绿洲区1穴1株、1穴2株和1穴3株种植方式对青贮玉米产量及水肥利用效率的影响。结果表明,1穴2株和1穴3株的地上生物产量均高于1穴1株,1穴2株最高,鲜重为102.9 t/hm~2,比1穴1株提高了29.4%;1穴2株与1穴1株之间存在显著差异(P0.05),1穴3株与1穴1株之间差异不显著(P0.05)。同样,1穴2株和1穴3株的地上生物产量水肥利用效率也均高于1穴1株,1穴2株的水分和氮肥利用效率也均最高,分别为9.3 kg/m~3和342.9 kg/kg;1穴2株与1穴1株之间存在显著差异(P0.05),1穴3株与1穴1株之间差异不显著(P0.05)。在河西走廊边缘绿洲区,采用1穴2株的种植方式能显著提高青贮玉米的地上生物产量和水肥利用效率,可在生产中推广应用。     

Improving adaptation to drought stress in white pea bean (Phaseolus vulgaris L.): Genotypic effects on grain yield,yield components and pod harvest index

Common bean (Phaseolus vulgaris L.) is the most important food legume crop in Africa and Latin America where rainfall pattern is unpredictable. The objectives were to identify better yielding common bean lines with good canning quality under drought, and to identify traits that could be used as selection criteria for evaluating drought‐tolerant genotypes. In all, 35 advanced lines were developed through single seed descent and evaluated with a standard check under drought and irrigated conditions at two locations over 2 years in Ethiopia. Grain yield (GY), pod number per m², seed number per m² and seed weight decreased by 56%, 47%, 49% and 14%, respectively, under drought stress. Eight genotypes had better yield with good canning quality under drought compared to the check. Moderate to high proportion of genetic effects were observed under drought conditions for GY and yield components compared to genotype × environment effects. Significant positive correlations between GY and pod harvest index (PHI) in drought suggest that PHI could be used as an indirect selection criterion for common bean improvement.     

Effect of organic and conventional farming systems on nitrogen use efficiency of potato,maize and vegetables in the Central highlands of Kenya

Increased per capita food production in the tropics is closely tied to soil organic matter and water management, timely nitrogen (N) supply and crop N use efficiency (NUE) which are influenced by farming systems. However, there is lack of data on the effect of organic farming systems on NUE and how this compares to conventional farming systems under tropical conditions. Therefore, the objectives of this study were to determine the effect of conventional and organic farming systems at low and high management intensities on N uptake and N use efficiency of potato (Solanum tuberosum L.), maize (Zea mays L.), cabbage (Brassica oleracea var. Capitata), kale (Brassica oleracea var. Acephala) and Swiss chard (Beta vulgaris sub sp. Cicla). The organic high input (Org-High) and conventional high input (Conv-High) farming systems are managed as recommended by research institutions while organic low input (Org-Low) and conventional low input (Conv-Low) farming systems are managed as practiced by small scale farmers in the Central highlands of Kenya. The study was conducted during three cropping seasons between October 2012 and March 2014 in an ongoing long-term trial established since 2007 at Chuka and at Thika, Kenya. Synthetic N-based fertilizer and cattle manure were applied at ∼225 kg N ha⁻¹ yr⁻¹ for Conv-High and at ∼50 kg N ha⁻¹ yr⁻¹ for the Conv-Low. Composts and other organic inputs were applied at similar N rates for Org-High and Org-Low. Nitrogen uptake efficiency (NUpE) of potato was highest in Conv-Low and Org-Low at Thika and lowest in Org-High and Org-Low at Chuka site where late blight disease affected potato performance. In contrast, the NUpE of maize was similar in all systems at Chuka site, but was significantly higher in Conv-High and Org-High compared to the low input systems at Thika site. The NUpE of cabbage was similar in Conv-High and Org-High while the NUpE of kale and Swiss chard were similar in the low input systems. Potato N utilization efficiencies (NUtE) and agronomic efficiencies of N use (AE_N) in Conv-Low and Conv-High were 11–21 % and 1.4–3.4 times higher than those from Org-Low and Org-High, respectively. The AE_N of maize was similar in all the systems at Chuka but was 3.2 times higher in the high input systems compared to the low input systems at the Thika site. The AE_N of vegetables under conventional systems were similar to those from organic systems. Nitrogen harvest index (NHI) of potato was similar between Conv-High and Org-High and between Conv-Low and Org-Low. N partitioned into maize grain was similar in all the system at Chuka, but significantly lower (P < 0.001) in Conv-low and Org-Low at Thika site. The NHI of cabbage in Org-High was 24 % higher than that of Conv-High. The study concluded that for maize and vegetables, conventional and organic farming systems had similar effects on NUpE, AE_N, NUtE and NHI, while for potato conventional systems improved NUE compared to organic systems. The study recommends that management practices for potato production in organic systems should be improved for a more efficient NUE.     

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.     

Effects of planting soybean in summer fallow on wheat grain yield,total N and Zn in grain and available N and Zn in soil on the Loess Plateau of China

Dryland wheat is the major contributor to wheat production in the world, where water deficiency and poor soil fertility are key factors limiting wheat grain yields and nutrient concentrations. A field experiment was carried out from June 2008 to June 2011 at Shilipu (latitude 35.12°N, longitude 107.45°E and altitude 1200 m above sea level) on the Loess Plateau (a typical dryland) in China, to investigate the effects of rotation with soybean (Glycine max) green manure (GM) on grain yield, total N and total Zn concentrations in subsequent wheat (Triticum aestivum L.), and on nitrate-N and available Zn in the soil. The benefits of crop rotation with soybean GM on wheat grain yields became more evident with time. In the second and third years, the grain yields of wheat rotated with soybean GM reached 4871 and 5089 kg ha⁻¹ at the 108 kg N ha⁻¹ rate. These yields were 21% and 12% higher than the highest yields of wheat under a fallow-winter wheat (FW) rotation. Rotation with soybean GM reduced the amount of N fertilizer required to obtain wheat grain yields and biomass levels similar to wheat grown in the FW rotation by 20–33%. In the first 2 years, average grain N concentrations over all N rates increased by 6% and 12%, and those of Zn increased by 26% and 14% under the soybean GM-winter wheat (SW) rotation, compared with the FW rotation. The increased grain N and Zn concentrations were found to be related to the increased concentrations of nitrate-N and available Zn in the soil, particularly at the sowing of winter wheat. However, grain N and Zn concentrations were not improved by rotation with soybean GM in the third year. This was attributed to the dilution effect caused by the more grain yield increase than its nutrient export. In conclusion, planting soybean for GM in fallow fields reduced the need for N fertilizer to enhance wheat yields in this dryland region. Change in wheat grain N and Zn concentrations was related to soil nutrient concentrations, and to the balance between increased grain yield and its nutrient export.