A review of farm-scale nutrient budgets for organic farms as a tool for management of soil fertility

Abstract. On organic farms, where the importation of materials to build/maintain soil fertility is restricted, it is important that a balance between inputs and outputs of nutrients is achieved to ensure both short-term productivity and long-term sustainability. This paper considers different approaches to nutrient budgeting on organic farms and evaluates the sources of bias in the measurements and/or estimates of the nutrient inputs and outputs. The paper collates 88 nutrient budgets compiled at the farm scale in nine temperate countries. All the nitrogen (N) budgets showed an N surplus (average 83.2 kg N ha^–1 yr^–1). The efficiency of N use, defined as outputs/inputs, was highest (0.9) and lowest (0.2) in arable and beef systems respectively. The phosphorus (P) and potassium (K) budgets showed both surpluses and deficits (average 3.6 kg P ha^–1 yr^–1, 14.2 kg K ha^–1 yr^–1) with horticultural systems showing large surpluses resulting from purchased manure. The estimation of N fixation and quantities of nutrients in purchased manures may introduce significant errors in nutrient budgets. Overall, the data illustrate the diversity of management systems in place on organic farms, and suggest that used together with soil analysis, nutrient budgets are a useful tool for improving the long-term sustainability of organic systems.     

湖北潮土区不同轮作制度下土壤养分平衡状况与评价

通过连续5年定点调查和取样分析,研究了湖北省2个潮土区域农田土壤养分平衡状况,并用允许养分平衡盈亏率进行了评价.结果表明:①在几种主要轮作制中,所有作物的K肥施用量及施用比例均明显比N肥低,但几乎所有作物的K素吸收量均明显高于N素吸收量,早、晚稻吸收P、K的比例明显高于其它作物.②不同轮作制中土壤养分平衡状况表现为N素有不同程度的盈余、P素基本平衡、K素总是亏缺的,且水田K素亏缺量明显高于早地.在此基础上,作者提出"减N稳P增K"和以一个轮作周期为单位进行统筹施肥的养分平衡调控措施,以实现作物生产的高产稳产和土壤养分平衡的良性循环.     

环渤海低平原农田生态系统养分循环与平衡研究

了解农田养分输入、输出和平衡状况,以及土壤肥力现状与变化特征,对实现养分资源优化管理、地力的持续提升、肥料利用率提高和农业可持续发展具有重要意义。基于1985年、2000年和2014年河北省南皮县国民经济统计资料,分析了从1985年到2014年县域农田生态系统养分循环与平衡状况;利用1981年第2次土壤普查和2015年实测南皮县域土壤耕层养分含量数据,探讨了耕层土壤养分变化及空间分布格局特征。结果表明,1985—2014年南皮县农田养分输入输出均呈持续上升趋势, NPK养分输入由10701 t增加至23386 t,年递增率2.33%; NPK养分来源结构略有不同, NP来源以化肥为主,其次是人畜粪尿和作物秸秆有机肥源;而K素来源主要是有机肥源。农田养分输出以作物吸收为主,占养分总输出的80%以上, NPK总输出由1985年的9093 t增加到2014年的18846 t,年均增速2.17%。从养分表观平衡的角度看,从1985年到2014年NP始终有大量盈余, P素盈余大于N素, N和P表观平衡率分别为16.8%~34.2%和26.9%~65.5%;若考虑有机氮的有效性问题,1985—2000—2014年3个时段有效氮盈亏率依次为18.1%、6.5%和-7.8%,有效氮平衡由盈余转向亏缺;而K素经历了由赤字逐渐向盈余的转变过程,由1985年的-33.5%赤字发展至2014年的33.6%盈余。受农田养分平衡状况的影响,南皮县土壤有机质、全氮、有效磷发生了显著变化,1981—2015年有机质由8.62 g·kg-1增至14.0 g·kg-1,增幅62.4%;全氮由0.542 g·kg-1增至0.908 g·kg-1,增幅67.5%;有效磷由2.0 mg·kg-1增加到20.8 mg·kg-1,增加了9.4倍。而碱解氮和有效钾变化不明显,分别由70.5 mg·kg-1和141 mg·kg-1增加到71.8 mg·kg-1和147 mg·kg-1,相对增幅仅为1.8%和4.2%。建议今后南皮县在农业生产中大力推广科学施肥技术,重视有机肥和化肥配施,推广秸秆还田,通过改进施肥方法提高肥料利用效率;养分管理中应提倡“稳氮、控磷、补钾”的施肥对策,避免过多的盈余养分进入环境。     

长江流域油?稻与麦?稻轮作体系周年养分收支差异

【目的】 评估1990—2017年长江流域不同轮作体系周年养分收支平衡,比较油?稻与麦?稻轮作体系养分收支差异,为提高周年养分利用效率、优化水旱轮作区域养分资源的合理分配提供依据。 【方法】 收集了长江流域[四川、重庆、贵州、湖北、湖南、江西、安徽、江苏、浙江和上海等省 (市)] 513个试验的油?稻与麦?稻轮作体系各季作物施肥量、生物量 (含秸秆和根茬及落叶归还)、养分含量、积累量,分析了油?稻与麦?稻轮作体系周年氮、磷、钾养分收支平衡,比较和评估了两种轮作体系氮的损失量 (包含NH₃挥发、N₂O排放以及氮的径流和淋溶)。 【结果】 油?稻轮作周年平均化肥投入量为N 378.5 kg/hm2、P₂O₅ 169.9 kg/hm2和K₂O 225.7 kg/hm2,麦?稻轮作为N 394.4 kg/hm2、P₂O₅ 172.5 kg/hm2和K₂O 210.8 kg/hm2,两种轮作方式施肥量未表现出明显差异。油?稻轮作还田生物量 (18984 kg/hm2) 高于麦?稻轮作 (18123 kg/hm2)。油?稻轮作周年养分归还量为N 142.5 kg/hm2、P₂O₅ 46.4 kg/hm2和K₂O 441.3 kg/hm2,较麦?稻轮作分别高出9.7%、6.7%和27.4%。落叶是油菜季养分归还量的重要部分,其带入的氮、磷、钾养分分别占到油菜还田养分总量的29.3%、18.5%和16.3%,使得油菜季养分输入量明显高于小麦季;而小麦由于群体生物量大,两种轮作模式水稻季的养分输入以麦?稻轮作优势明显 (钾素除外)。麦?稻轮作周年地上部养分带走量为N 333.9 kg/hm2、P₂O₅ 125.8 kg/hm2和K₂O 379.3 kg/hm2,分别较油?稻轮作高出14.6%、2.1%和?13.4%。油?稻与麦?稻轮作周年氮损失量分别为N 96.7和88.8 kg/hm2,占周年施氮量的22.5%～25.5%。油菜季氮损失量平均N 34.5 kg/hm2,略高于小麦季的N 29.8 kg/hm2。水稻季氮损失量明显高于旱季作物,两种轮作体系相差较小 (N 59.0～62.2 kg/hm2)。不同氮损失途径中,NH₃挥发损失的氮所占比例最大,占各季施氮量的7.2%～18.4%;其次是氮的淋溶和径流损失,约为6.7%～12.7%;N₂O排放所占比例最小 (1.1%～2.1%)。秸秆不还田时,油?稻轮作体系氮素盈余N 37.3 kg/hm2,麦?稻体系持平或略有亏缺 (N ?6.0 kg/hm2),两种轮作体系P₂O₅盈余53.3～58.4 kg/hm2、K₂O亏缺138.3～145.0 kg/hm2。秸秆还田后,油?稻轮作体系周年养分收支平衡量为N 133.0 kg/hm2、P₂O₅ 93.1 kg/hm2和K₂O 229.0 kg/hm2,分别较麦?稻轮作高出30.9%、3.2%和28.7%。 【结论】 水旱轮作体系在秸秆不还田时,油?稻体系氮盈余,麦?稻体系氮持平或略有亏缺,两个体系磷均有盈余而钾素处于亏缺状态。秸秆还田时,两种轮作体系氮、磷、钾均表现为盈余,说明秸秆还田能够增加养分输入,维持土壤养分的平衡。由于油菜落叶归还大量氮素,油?稻轮作较麦?稻轮作体系氮素盈余量高,因此,油?稻轮作可考虑降低氮肥的施用。      

不同施肥模式对作物-土壤系统养分收支的影响

以1 组20 年长期定位试验为基础, 针对不同施肥模式下作物-土壤系统养分收支状况进行研究。本试验共8 个处理, 分别由化肥氮(N)、磷(P)、钾(K)和循环有机肥(M)组合而成。结果表明, 养分循环再利用有利于作物产量的提高, 对大豆和玉米籽实平均增产率分别为22.9%和16.4%; 但随化肥的均衡施用, 有机肥增产作用明显降低。仅施用循环有机肥可缓解土壤养分收支赤字, 但无法实现作物高产和土壤养分收支平衡; 施用氮肥加剧土壤磷收支赤字, 同时施用氮、磷肥加剧土壤钾赤字。本研究中同时施用氮、磷、钾肥和循环肥模式可满足作物高产的养分需求, 同时能够平衡土壤养分收支, 是较为理想的施肥模式。     

Long-term fertilizer trials on loam soil at M⊘ystad,south-eastern Norway: Crop yields,nutrient balances and soil chemical analyses from 1983 to 2003

Abstract

Factorial combinations of N, P and K fertilizer have been compared with the use of farmyard manure at M?ystad since 1922 in a seven-year crop rotation (3 ley, oat, potato, wheat, barley). Until 1982, low inputs of N fertilizer (22 kg ha^?1) were used. In 1983, they were brought into line with current farming practice. This paper presents the results of three subsequent rotations. Yields without any fertilizer were on average 48% of those with 100 kg N ha^?1 in compound fertilizer, whilst those with 20, 40 and 60 Mg ha^?1 farmyard manure were 81, 87 and 90%, respectively. Yields with other combinations of N, P and K declined in the order NP, NK, N, PK and K. When NPK fertilizer was used, apparent recoveries of applied fertilizer were close to 50% for N and K, and around 40% for P. Much lower values were found for nutrients applied singly. Balance between N supply and removal was indicated at rates of about 60 kg N fertilizer ha^?1 in potatoes, 75 kg ha^?1 in cereals and 90 kg ha^?1 in leys. A surplus of P was found in all crops at all N levels, and of K in cereals and potatoes. In leys, K balance was achieved with an N supply of 90 kg N ha^?1. Nutrient balance was indicated at a little below 20 Mg ha^?1 yr^?1 farmyard manure. Larger manure applications gave large nutrient surpluses, particularly of N. Soil reaction remained close to neutral with the use of calcium nitrate and manure, but declined with the use of ammonium nitrate. Manure use gave the highest amounts of available P, K and Mg in soil. Similar increases in total inorganic P were found with manure use as with fertilizer use, but amounts of organic P and total K were little affected.     

等氮配施有机肥对喀斯特峰丛洼地农田作物产量与养分平衡的影响

基于自2006年在广西喀斯特峰丛洼地区开展的长期玉米/大豆套作定位施肥试验,选择2010—2014年监测数据,探讨等氮量投入条件下,不同比例有机肥替代无机氮肥对喀斯特峰丛洼地玉米/大豆套作系统作物产量及土壤养分的影响,为喀斯特峰丛洼地农田作物高效施肥及提高土壤肥力提供理论依据。试验选取4个处理:对照(不施肥,CK)、平衡施用化肥(NPK)、有机粪肥替代30%化肥氮(C7M3,按氮素计算,不足30%的PK用无机肥补充,肥料总量与NPK处理相同,有机粪肥为牛粪,下同)、有机粪肥替代60%化肥氮(C4M6,按氮素计算,不足60%的PK用无机肥补充),每个处理4次重复。于2010年、2012年、2014年大豆收获后采集土壤样品,测定土壤养分状况。结果表明:1)施肥处理土壤有机质、全氮、速效磷及速效钾含量均高于CK处理,其中C4M6处理有机质含量显著高于NPK处理(P0.05),全氮、速效磷和速效钾含量随着有机粪肥施用量的增加而增加。2)长期不同施肥处理玉米和大豆产量分别是不施肥处理的4.15~4.36倍、2.47~2.58倍。不同施肥处理的增产效果为C4M6NPKC7M3,但施肥处理间差异不显著(P0.05)。3)长期不施肥CK处理玉米产量随着试验年限推移呈下降趋势,降幅为5.45 g·m~(-2)·a~(-1),大豆产量却表现出增加趋势,增幅为1.50 g·m~(-2)·a~(-1)。长期施肥处理中,玉米和大豆产量总体呈增加趋势。4)施肥处理中,玉米季表现为钾素亏缺(NPK处理除外),大豆季表现为氮素亏缺。综合两季作物,只有C4M6钾素表现亏缺,亏缺量为7.9 kg·hm~(-2)。磷素在各施肥处理中盈余量较大,分别为81.2 kg·hm~(-2)(NPK)、83.4 kg·hm~(-2)(C7M3)和74.8 kg·hm~(-2)(C4M6)。综上,在喀斯特峰丛洼地玉米/大豆套作制度下,基于作物产量及土壤养分表观平衡特征提出有机粪肥可以代替部分化肥施用,在玉米季适当"减氮、稳磷和增钾",大豆季"稳氮、减磷和减钾"的施肥措施。     

长期施氮、磷、钾化肥对玉米产量及土壤肥力的影响

以1990年建立的国家褐潮土土壤肥力与肥料效益长期监测基地(北京昌平站)的长期肥料定位试验为研究平台,研究了不同施肥制度对玉米产量和土壤肥力的影响。结果表明,长期均衡地施NPK肥或NPK与有机肥配施,可以显著提高玉米产量和土壤有机质、全氮、全磷、速效氮、速效磷、速效钾等肥力指标,并能提高土壤微量元素的含量;而不均衡施肥(N、NK、NP、PK)导致相应的营养元素的耗竭。相关分析表明,在褐潮土上增施磷肥和有机肥对提高玉米产量具有重要的作用。     

京郊畜禽粪肥资源现状及其替代化肥潜力分析

随着都市型规模化养殖业快速发展,畜禽粪尿废物大量排放因缺乏足够面积土地消纳所带来的环境压力很大,而粪尿中的氮磷钾养分与化肥一样对作物同等重要,如何合理利用这些废物资源决定了都市化农业的可持续发展。该文针对京郊养殖业和农用地面积现状,结合调研、收集畜禽养分排泄系数和农田养分需求等参数,估算京郊固液粪便养分资源现状及其替代化肥的潜力。结果表明:京郊畜禽固液粪便中N、P、K养分量分别为58.7×103、21.3×103、29.8×103 t,其中固体粪便N、P、K养分分别为43.1×103、20.3×103和19.7×103 t,京郊畜禽固液粪便可分别满足农田N、P、K养分需求量的99.3%、185.2%、62.7%。大部分区县粪肥中P养分产生量超过作物P需求量,粮田秸秆还田可带入的N、P、K养分分别为11.0×103、1.6×103和15.0×103 t,情景分析表明在秸秆还田条件下,按照磷素平衡原则估算本地区所能消纳的粪肥所带入N、P和K养分数量分别为18.3×103、9.9×103和10.3×103 t,同时需要补充N、K化肥分别为29.8×103和22.2×103 t,其余粪肥则需经过堆肥化处理并输往外地。经过堆肥处理,固体粪肥可提供的N、P、K养分分别下降了23%、11%和12%,外输固体粪肥堆肥可进一步减少农田氮磷负荷以及可能的环境风险。     

长期施肥褐土有效磷对磷盈亏的响应

【目的】研究长期施肥条件下土壤磷素供应能力、累积状况与土壤有效磷变化速率,阐明土壤磷素累积与土壤有效磷的响应关系,为黄土高原旱作农业区科学施用磷肥提供理论依据。【方法】以农业部寿阳旱作农业示范区褐土肥力与肥料长期定位试验为研究平台,选择试验中9个处理进行研究分析,分别为不施肥处理(CK)、4个单施无机肥水平处理(N_1P_1、N_2P_2、N_3P_3、N-4P_4),3个有机无机肥配施水平处理(N_2P_1M_1、N_3P_2M_3、N-4P-2M_2)单施有机肥处理(N_0P_0M-6)。以5年一个周期测定土壤0-20 cm有效磷含量,明确土壤有效磷的变化规律。计算玉米收获后植株生物量以及测定磷含量得出作物携出量与磷素年累积量,分析不同施肥处理下土壤磷素盈亏与土壤有效磷的变化特征。【结果】长期不施用磷肥情况下,土壤磷素一直处于亏缺状态,有效磷年均下降速率为0.02mg/(kg·a)。单施无机肥后,随着磷肥投入量的增加,土壤有效磷随之增加,N_1P_1、N_2P_2、N_3P_3、N_4P_4处理年均增速分别为1.04、1.08、1.70和2.13 mg/(kg·a)。有机无机配施处理土壤有效磷普遍高于单施化学磷肥处理含量,N_2P_1M-1、N_3P_2M-3、N_4P_2M_2处理年均升高速率分别达1.70、3.73和4.72 mg/(kg·a)。单施高量有机肥N_0P_0M_6处理土壤中有效磷增速最高,年均升高5.63 mg/(kg·a)。长期不施肥导致土壤磷素亏欠,土壤中每亏缺P 100 kg/hm~2,土壤中有效磷含量平均降低0.5 mg/kg。施用无机肥条件下,土壤每累积P 100 kg/hm~2,土壤中有效磷含量可以平均提高4.3 mg/kg。有机无机配施有协同作用,其土壤P每累积100 kg/hm~2,土壤有效磷含量平均提高9.1 mg/kg。N_2P_1M_1处理为推荐施肥处理,即每年投入P_2O_5 65 kg/hm~2,后土壤有效磷增加最多,土壤每累积P100 kg/hm2,土壤中有效磷含量平均提高17.1 mg/kg。【结论】土壤有效磷随土壤磷素盈余而变化,同时与磷素投入量密切相关,当P_2O_5;每年投入量为37.5~65 kg/hm~2时基本可以满足作物生长需求磷肥当季利用率较高,磷素在土壤中累积量较少。当P_2O_5;每年投入量达到112 kg/hm~2,后会造成磷素在土壤中大量累积不仅作物产量对磷肥几乎没有响应还会对农田环境产生危害。     

长期不同施肥紫色水稻土磷的盈亏及有效性

【目的】 研究长期施肥条件下土壤全磷、有效磷 (Olsen-P) 对磷素盈亏的响应,为西南紫色水稻土区科学施用磷肥提供依据。 【方法】 以四川遂宁34年 (1982—2015年) 长期肥料定位试验为平台,试验设8个处理,即不施肥 (CK)、氮肥 (N)、氮磷肥 (NP)、氮磷钾肥 (NPK)、有机肥 (M)、有机肥 + 氮肥 (MN)、有机肥 + 氮磷肥 (MNP) 和有机肥 + 氮磷钾肥 (MNPK),分析了土壤磷素盈亏与全磷、Olsen-P的变化特征。 【结果】 不施磷肥 (CK和N) 作物每年从土壤中带走磷约13.22 kg/hm2,且维持在较低的变化水平;单施有机磷肥处理 (M与MN) 作物携出磷量比不施磷肥提高了约1.73倍,磷素携出量呈增加趋势;施用磷肥 (NP、NPK、MNP和MNPK) 作物携出磷量在41.71～45.62 kg/hm2之间,吸磷量随时间呈下降趋势。不施磷肥土壤磷素常年处于亏缺状态,施磷土壤磷素年均盈余量为8.76～88.79 kg/hm2,有机无机磷肥配施磷盈余量大于单施有机肥和单施无机磷肥,随施肥年限的延续磷盈余量呈上升趋势。土壤中磷含量随磷盈亏而变化,施用无机磷肥或有机无机磷肥配施土壤全磷和Olsen-P增量与磷盈亏呈显著正相关,而不施磷或单施有机磷这种响应关系不明显;土壤每盈余磷100 kg/hm2,NP、NPK、MNP和MNPK处理土壤中全磷分别增加0.14、0.16、0.015和0.018 g/kg,Olsen-P分别提高15.76、17.19、1.96和1.85 mg/kg。 【结论】 土壤磷素有效性随土壤磷素盈亏而变化,与加入磷素形态密切相关,西南紫色水稻土单施无机磷肥提升土壤磷含量的速率大于施用有机肥。      

沼肥替代化肥对设施蔬菜产量和土壤养分及重金属累积的影响

针对盲目施用沼肥可能带来的土壤环境问题,该研究采用5年8茬的设施番茄-甜椒田间轮作试验,研究不同沼肥和化肥配比对蔬菜产量、设施土壤氮磷养分及重金属累积的影响.结果表明:在等氮钾养分投入下,沼肥和化肥以不同比例配施的各处理没有影响蔬菜产量;氮素盈余和0~180cm土层土壤全氮含量随沼肥施用比例增加没有显著差异;磷素盈余随沼肥施用比例增加显著增加,完全沼肥处理0~30cm土层土壤Olsen-P及CaCl2-P含量分别达到151和8.0mg/kg,高于其他2个处理,且明显超出环境阈值.与完全沼肥处理相比,减量沼肥施用(3/5沼肥处理)明显降低了土壤氮素淋洗风险和磷素累积.与不施肥处理相比,施用沼肥后30~60、60~90、150~180cm土层土壤全Hg含量均低于不施肥处理;除30~60cm土层使用沼肥处理土壤中全As含量显著高于不施肥处理,其他土层各处理间均没有显著差异,而完全沼肥处理全Cr、全Cd、全Pb含量有所下降,且全Pb含量下降最为显著,但均没有出现重金属污染风险.沼肥替代化肥施用可有效实现废弃物中的养分资源循环利用,但增加菜田土壤磷素累积和淋失风险,本研究为设施菜田合理施用沼肥提供技术支持,为实现沼肥资源的循环利用和化肥替代模式提供理论参考.     

不同施肥制度对作物产量及肥料贡献率的影响

通过17年的长期定位肥料试验,研究了不同施肥制度对作物产量及肥料贡献率的影响,结果表明:化肥N、P、K的施用均能明显提高作物产量,其增产率分别为32.10%、15.06%、10.95%;循环回田的农家肥养分对作物增产有明显的残效叠加作用,且具有良好的稳产作用,可以满足作物对不同气候年景的适应性。在本试验中,若将保持养分循环再利用基础上施用NPK化肥视为最佳施肥制度,则在保持其他农业技术不变条件下,最大施肥贡献率为0.44。在下辽河平原土壤、气候和生产力水平等条件下,为保证作物持续高产,应同时施用化肥和循环肥。     

京郊畜禽粪污氮磷含量特征及影响因素分析

中国规模化养殖废弃物中养分资源数量可观,但缺乏循环利用技术,处置不当易引发环境污染问题。该文通过问卷调研和粪污样品检测,对京郊典型养殖场粪便和废水中的总氮、总磷含量特点进行分析,同时追踪典型规模化猪场废水中总氮、总磷含量变化的影响因素及其季节性变化特征。结果表明:所调研的养殖场中,猪粪、牛粪的总氮质量分数平均值分别为29.1,17.8 g/kg,总磷质量分数平均值分别为15.1,6.8 g/kg,猪粪便的总氮、总磷含量变异程度大于牛粪;猪场和牛场中废水总氮、总磷质量分数的平均值分别为892,540和82.4,53.3 mg/L,猪场废水总氮、总磷含量变异程度明显大于牛场。规模化猪场粪便总氮、总磷含量受到饲料配方的影响较大;受饲料和圈舍用水量的影响,现行饲养工艺及粪污处理方式下粪便对废水中总氮、总磷含量的影响较小;万头以上的规模化猪场废水中总氮、总磷含量存在季节性差异,且随着废水存储时间的推移其无机磷比例增加。这些变化特征可对畜禽粪便和养殖废水的资源化再利用提供了有用的参考。     

Characterizing farming systems around Kakamega Forest,Western Kenya,for targeting soil fertility–enhancing technologies

Kakamega district in Western Kenya represents the smallholder farming systems typical for much of the densely populated humid highlands in East Africa. A specific feature, however, is the presence of a protected forest reserve (Kakamega Forest National Park), covering some 20% of the district area. Year‐round crop production with little use of external inputs is resulting in declining soil fertility and crop yields. Technologies to counteract fertility constraints are rarely implemented, as they do not consider system diversity or farm‐specific characteristics. We surmised that farm type–specific targeting of technology options to address soil fertility–related production constraints would reduce the anthropogenic pressure on the resources of the adjacent Kakamega rainforest reserve. Based on Kenyan national census data, we selected 168 farms in physical proximity of the Kakamega forest and characterized them regarding production system and soil attributes. Cluster and principal component analyses identified five distinct farm categories. Three representative farms from each cluster group were subsequently selected to establish labor‐use patterns, draw resource‐flow maps, and determine NPK balances. Small subsistence‐oriented farms were most common (> 50%), with maize yields of 0.9 t ha^–1 (Cluster 1). Most farmers relied on the forest to provide fire wood, animal feed, and medicinal plants. Mixed farms, combining subsistence maize with industrial crops, were differentiated by soil type, with tea being grown on Ferralsol (Cluster 3), and sugar cane being grown on Acrisol (cluster 4). The dependence on forest resources was limited to animal grazing and the collection of feed stuff (Cluster 3), or the extraction of medicinal plants (Cluster 4). Only few farms showed a high degree of market orientation of the food‐crop production. These comprised either small farms with high investments in fertilizer and maize yields close to 2 t ha^–1 (Cluster 2), or larger farms (1.6–3.9 ha) with low fertilizer but high hired‐labor use (Cluster 5). Their reliance on forest resources was generally low. Resource flows showed mainly patterns of nutrient export in subsistence farms, and more complex flow patterns, involving several farm compartments, in the diversified farms. Partial nutrient balances were strongly negative for N and K, irrespective of soil or farm type. Soil‐fertility characteristics reflected the nutrient balances with generally low C and N in all farms on Acrisol, and low P in farms not applying mineral fertilizers or farmyard manure. The proposed typology is expected to improve the targeting of technologies addressing soil fertility–related production constraints, and to reduce the pressure on forest resources. This is of particular importance in the case of small‐scale subsistence and mixed farms close to the forest margin.     

Phosphorus cycling in UK agriculture and implications for phosphorus loss from soil

Abstract. Phosphorus (P) use in UK agriculture is reviewed and a P balance sheet presented. The productive grassland and arable area has accumulated an average P surplus of c. 1000 kg ha^–1 over the last 65 years. Over the period 1935–1970, the annual P surplus more than doubled due to an increase in animal numbers and associated requirements for inorganic fertilizers and livestock feeds. Since 1970, surplus P has declined by c . 40% as crop yields and P offtake have continued to increase while fertilizer and manure P inputs have remained relatively constant. In 1993, P use efficiency (P imports/P exports) in UK agriculture was estimated at 25% leading to an average annual surplus of 15 kg P ha^–1 yr^–1, although the latter has since decreased slightly due to reduced fertilizer use. Intensification and specialization of agriculture has also increased the range in P surpluses that are likely between livestock and arable dominated systems. The largest P surpluses occur in the relatively limited areas of arable soils which receive manure from intensive pig and poultry units, whilst farms without manure inputs generate only small surpluses, or are in balance. The cumulative P surplus has led to a build-up of soil total and easily-exchangeable P, especially in areas receiving both fertilizers and manures. Fundamental differences in P use efficiency, surplus P accumulation and the potential for P loss to water, exist between arable and grassland farms and it is important to separate these, due to the marked regionalization of UK agriculture. More judicial use of feeds and fertilizers is required to further reduce the P surplus and minimize the long-term risk of water eutrophication.     

Nitrous oxide emissions and nitrogen cycling in managed grassland in Southern Hokkaido,Japan

Abstract

Nitrous oxide (N₂O) emissions were measured and nitrogen (N) budgets were estimated for 2?years in the fertilizer, manure, control and bare plots established in a reed canary grass (Phalaris arundinacea L.) grassland in Southern Hokkaido, Japan. In the manure plot, beef cattle manure with bark was applied at a rate of 43–44?Mg fresh matter (236–310?kg?N)?ha^?1?year^?1, and a supplement of chemical fertilizer was also added to equalize the application rate of mineral N to that in the fertilizer plots (164–184?kg?N?ha^?1?year^?1). Grass was harvested twice per year. The total mineral N supply was estimated as the sum of the N deposition, chemical fertilizer application and gross mineralization of manure (GMm), soil (GMs), and root-litter (GMl). GMm, GMs and GMl were estimated by dividing the carbon dioxide production derived from the decomposition of soil organic matter, root-litter and manure by each C?:?N ratio (11.1 for soil, 15.5 for root-litter and 23.5 for manure). The N uptake in aboveground biomass for each growing season was equivalent to or greater than the external mineral N supply, which is composed of N deposition, chemical fertilizer application and GMm. However, there was a positive correlation between the N uptake in aboveground biomass and the total mineral N supply. It was assumed that 58% of the total mineral N supply was taken up by the grass. The N supply rates from soil and root-litter were estimated to be 331–384?kg?N?ha^?1?year^?1 and 94–165?kg?N?ha^?1?year^?1, respectively. These results indicated that the GMs and GMl also were significant inputs in the grassland N budget. The cumulative N₂O flux for each season showed a significant positive correlation with mineral N surplus, which was calculated as the difference between the total mineral N supply and N uptake in aboveground biomass. The emission factor of N₂O to mineral N surplus was estimated to be 1.2%. Furthermore, multiple regression analysis suggested that the N₂O emission factor increased with an increase in precipitation. Consequently, soil and root-litter as well as chemical fertilizer and manure were found to be major sources of mineral N supply in the grassland, and an optimum balance between mineral N supply and N uptake is required for reducing N₂O emission.     

中国农业生态系统氮磷钾平衡时空变异研究

Nitrogen, phosphorus, and potassium balances for agroecosystems in China from 1993 to 2001 were calculated at national and provincial levels using statistical data and related parameters, and their spatial and temporal variabilities were analyzed with GIS to estimate the potential impacts of nutrient N, P and K surpluses or deficits to soil, water and air. At the national scale, the N and P balances from 1993 to 2001 showed a surplus, with the nitrogen surplus remaining relatively stable from 1997-2001. Although during this period the P surplus pattern was similar to N, it had smaller values and kept increasing as the use of phosphate fertilizer increased year by year. However, K was deficient from 1993 to 2001 even though from 1999 to 2001 the K deficit decreased. The spatial analysis revealed higher N surpluses in the more developed southeastern provinces and lowest in the western and northern provinces where there was less chemical fertilizer input. The serious K deficit mainly occurred in Shanghai and Beijing municipalities, Jiangsu, Zhejiang and Hubei provinces, and Xinjiang autonomous regions. For the years 1992, 1996 and 2001, N surpluses and K deficits had significant positive spatial correlations with per capita gross domestic product (GDP), per capita gross industrial output value, and per capita net income of rural households. This showed that the level of economic development played an important role on nutrient balances in the agroecosystems.     

The fertilizer equivalence of phosphorus and potassium in organic manures applied to arable soils

Previous papers [Soil Use and Management (2004) vol. 20, 410; (2007) vol. 23, 162] derived relationships for different soil types in south England of change in topsoil K (ΔKex) or P (ΔPres) against K or P balance over 3–5 years for fields in commercial farms given variable rates of fertilizer but no manure. Shown here is how ΔKex or ΔPres on manured fields can be converted to a fertilizer equivalent (fertilizer substitute) K or P value of the manure (FEK or FEP). There were significant increases in Pres and Kex when animal manures were applied, and in Pres using sewage sludge cake or liquid. Median FEP and FEK values for one application were – cattle farm yard manure (FYM) 36 kg P per hectare and 153 kg K per hectare, pig manure 70 and 149, digested sludge cake 62 P and digested liquid 31 P. Poultry manures and slurries also showed a significant benefit. When <12 months (only one cultivation) elapsed between application and soil sampling, FEP was much lower than in the second year and further increased over 4 years, whereas the maximum FEK was attained within a year of manure application. Release of P is slow compared with K. After 2–4 years FEP and FEK per tonne of FYM calculated as 0.95 kg P and 4.5 kg K, but farmer-reported application rates may be inaccurate. For biosolids <60% of the total P showed as FEP within 4 years. Even single manure applications register a large benefit in soil P and K supply (currently worth >£225 per hectare as fertilizer), but are variable in effect, which must be evaluated by soil analysis: at least one season and two cultivations should elapse before sampling; ideally more than a 2-year interval.     

藏东南大型国营农场土壤肥力现状及培肥措施

藏东南大型国营农场———米林农场土壤养分含量明显下降 ,有机质、碱解氮、有效磷、有效钾分别较 1992年降低49 4% ;49.3 % ;47.8% ;72 .5 %。下降的主要原因是施肥水平低 ,化肥利用率不高 ,种植结构单一。因此 ,大量施用有机肥 ,合理施用化肥 ,调整种植结构 ,扩种绿肥是培肥该农场土壤的主要措施