氮肥用量对旱地冬小麦产量及夏闲期土壤硝态氮变化的影响

在陕西渭北旱塬,利用长期定位试验研究了长期不同氮肥用量（0、80、160、240、320 kg hm-2）对旱地冬小麦产量形成,氮素利用,土壤硝态氮残留、夏闲期淋溶和矿化的影响。结果表明：随用量增加,施氮提高旱地小麦产量的效应下降,而土壤硝态氮残留迅速增加。作物生长当季的硝态氮残留主要分布在0～60 cm土层,施氮超过160 kg hm-2时,达56.8～211.7 kg hm-2,来源于当季施用氮肥的残留占64%～90%。夏闲期土壤硝态氮发生淋失的土层深度和硝态氮淋失量均与施氮量呈显著的抛物线关系（r = 0.988 9和0.994 0）,施氮量超过160 kg hm-2时,每增加100 kg hm-2的氮肥投入,硝态氮淋失深度和淋失量增加量分别高于27 cm和80.4 kg hm-2。平均每10 mm的夏闲期降水可使离开原土层发生淋溶的硝态氮向下移动2～4 mm。施氮量对硝态氮淋失的深度没有显著影响。夏闲期土壤氮素矿化量、来源于当季施入土壤肥料氮被生物固定后的再矿化量分别为51.8～160.9 kg hm-2和31.6～109.2 kg hm-2。基于本研究,建议渭北旱塬冬小麦施氮量控制在146～163 kg hm-2,以保证旱地小麦高产,防止过量肥料氮残留,减少淋溶风险。     

Nitrate leaching in field lysimeters at an agricultural site in Zimbabwe

Abstract. Nitrate leaching in lysimeters containing a tropical sandy agricultural soil was studied over two summers with maize ( Zea mays L.) and one winter season with wheat ( Triticum aestivum L.). The treatments included two moisture regimes and two nitrogen sources, cattle manure and inorganic fertilizer-N (either ammonium nitrate or ammonium sulphate) applied at 100 kg N/ha in the summers. Neither manure nor fertilizer-N was applied in the intervening winter. Leachate volume from the manured lysimeters was mostly larger than from fertilized ones because of poor growth and less evapotranspiration. The largest seasonal nitrate loads (17–39 kg N/ha) were obtained in the wet summer immediately after installation of the lysimeters. Nitrate loads in winter (3.7–18.6 kg N/ha) were larger than those obtained in fertilized (0.6 and 9.3 kg N/ha) and manured (0.3 and 3.0 kg N/ha) lysimeters for the two moisture regimes in the second summer. The drier conditions in the second summer decreased N-mineralization and leaching of manure.     

降雨对吉林省黑土区雨养春玉米农田氮磷淋溶的影响

吉林省黑土区是我国玉米生产的重要基地,农业集约化程度较高,农业面源污染风险较大。因此,掌握吉林省黑土区降雨与农田氮磷淋溶的关系,对区域生态农业可持续发展意义重大。本研究基于吉林省4个面源污染监测点,于2016-2019年春玉米季对降雨情况、淋溶量、淋溶液氮磷浓度及淋溶强度等进行了动态监测,系统分析了吉林省黑土区自然降雨与农田氮磷淋溶的关系。结果表明:1)吉林省黑土区降雨年际间和监测点间差异较大,年际间波动在424～554mm,春玉米全生育期平均降雨量为475mm;不同监测点降雨量大小依次为通化(593～785 mm)公主岭(512～699 mm)梨树(305～434 mm)农安(197～342 mm)。2)淋溶量和降雨强度呈极显著正相关关系,降雨强度每增加10 mm·(24h)-1,淋溶量增加1.81mm。全生育期(4-10月)降雨量与淋溶次数、淋溶概率分别呈极显著和显著正相关,降雨量每增加100mm,淋溶次数约增加3次,淋溶概率上升6%。当全生育期降雨量超过74mm时,淋溶概率增加,可能引起淋溶;而当全生育期降雨量达到217mm时,淋溶次数增加,可以发生淋溶。产生淋溶的降雨等级一般以中雨(10～24.9 mm)和大雨(25～49.9 mm)为主。3)淋溶量和淋溶液总氮浓度呈极显著正相关,与总磷浓度无明显相关关系。4)总氮淋溶强度与降雨强度呈极显著正相关,降雨强度每增加10 mm·(24h)-1,总氮淋溶强度增加0.73kg·hm~(-2),而总磷淋溶强度与降雨强度无明显相关性。由此可见,吉林省黑土区农田在春玉米雨养条件下以氮素淋溶为主,且与降雨密切相关,应因地制宜采取农艺措施在源头上阻控农业面源污染的发生,为农业生态可持续发展提供有效途径。     

施磷对苦麦菜生长及土壤磷素淋失的影响

利用网室土柱模拟试验, 研究了不同磷用量[0、0.05 g·kg^-1(土)、0.10 g·kg^-1(土)、0.20 g·kg^-1(土)]对苦麦菜产量、磷素吸收和利用及土壤磷淋失的影响。结果表明, 施磷显著增加苦麦菜产量、促进植株对磷的吸收。苦麦菜产量在低磷水平[0.05 g·kg^-1(土)]时最高, 为每个土柱186.29 g。随磷用量增加, 苦麦菜产量和磷肥利用率明显降低, 植株吸磷量无明显变化。施磷显著增加土壤磷淋失量, 且随磷用量增加, 不同形态磷淋失量均显著增加。同一磷处理颗粒磷淋失量高于溶解态磷。不同磷用量条件下土壤各形态磷的淋失率均低于0.1%。低量施磷条件下溶解态磷在施磷后第10 d 出现第1 次淋失高峰; 中量和高量施磷条件下溶解态磷在施磷后第10 d 和第40 d 分别出现2 次淋失高峰。土壤总磷和颗粒磷淋失高峰期在施磷后第40~50 d 出现。施肥后第60 d, 土壤总磷、溶解态磷和颗粒磷淋失浓度均明显降低。综合考虑苦麦菜产量、磷素吸收和利用及土壤磷淋失量等因素, 苦麦菜以0.05 g·kg^-1(土)的施磷量为佳。     

水肥管理及生物炭施用对作物产量和磷效率及磷淋失的影响

为探讨中国北方褐土区典型种植模式——冬小麦-夏玉米体系水分优化、养分优化以及生物炭施用对作物产量、磷效率和磷素淋失的影响,2016—2019年于陕西杨凌土(黄土母质,自然褐土发育)区进行田间渗漏池试验,设计习惯水肥(CP1、CP2, CP1处理渗漏池深为120～150 cm, CP2处理渗漏池深为100 cm)、灌水优化(CP1-W)、养分优化(CP1-F)、水分养分优化(OPT)、习惯水肥+生物炭(CP2+B)以及水分养分优化+生物炭(OPT+B)7个处理,研究作物产量、磷肥偏生产力和磷素淋失的响应。结果表明,CP1-W、CP1-F和OPT处理3年平均冬小麦、夏玉米及作物总产量均与CP1处理无显著差异。CP1-F和OPT处理较CP1处理均显著增加磷肥偏生产力,平均增幅分别为69.3%和56.4%。与CP1处理相比, CP1-W和CP1-F均没有显著影响各形态磷的淋失量,而OPT处理的颗粒磷淋失量显著减少58.4%。施用生物炭对3年平均作物总产量无显著影响,而在CP2+B处理磷肥偏生产力显著提高43.6%;在OPT+B处理磷肥偏生产力无显著变化。CP2+B处理各形态磷素的淋失量均与CP2处理相似, OPT+B处理第1年可溶性有机磷、颗粒磷和总磷淋失量较OPT处理分别显著降低60.0%、57.1%和62.4%,但后两年OPT+B处理总磷淋失量却显著增加。综合3年的结果发现,在不同条件下施用生物炭对各形态磷素淋失均无显著影响。上述结果表明,褐土区在农户水肥的基础上合理降低水肥用量,可以提高磷肥利用率,降低磷素淋失量,保障作物产量;而施用冬小麦秸秆生物炭对作物产量、磷素淋失无显著影响,对磷肥偏生产力的影响结果不一致,有待进一步研究。     

不同水氮用量对日光温室黄瓜季硝态氮淋失的影响

于2010年3～7月,在河北省辛集市马庄农场研究了不同水氮用量对黄瓜季硝态氮淋失的影响,结果表明,通过调节不同生育阶段灌水量使黄瓜全生育期土壤含水量保持在18.7%～22.1%,不仅可以满足黄瓜生长发育对土壤水分的要求,而且可以减少用水量30%。不同处理中以节水灌溉、习惯施氮处理（W2N1）土壤硝态氮含量最高,习惯灌水、减量施氮处理（W1N2）最低。全生育期内,土体95cm深度硝态氮淋失量与土壤含水量、土壤硝态氮含量均呈正相关,其中以初瓜期和盛瓜期相关性系数最高。与农民习惯水氮处理（W1N1）相比,节水减氮处理（W2N2）在节水30%减施氮25%的情况下,可以显著降低黄瓜季土壤硝态氮淋失量,整个生育期降低淋失量35.0%。3年连续试验结果表明,节水减氮处理（W2N2）与习惯水氮处理（W1N1）间黄瓜产量结果差异不显著,说明河北省温室大棚蔬菜生产,目前农民习惯施氮和灌水量有很大的节水节肥空间,根据蔬菜不同生育期需肥量和土壤含水量来合理分配水、氮可取得明显的节水节氮效果。     

Dairy manure treatment effects on manure phosphorus fractionation and changes in soil test phosphorus

In this research, a sequential fractionation procedure coupled with enzyme hydrolysis was used to categorize the phosphorus (P) forms of 18 manure samples collected from in-barn composted bedded pack (beef manure), anaerobic digestion with liquid–solid separation (dairy manure), and liquid–solid separation systems (dairy manure). This research also determined the effects of those P forms on the increase in soil test P (STP) of five soil series. The soils used had initial Bray-1 P ranging from 16 to 43 mg P kg^?1. Total dry-ash P (P_t) of the manures ranged from 1.4 to 15.0 g P kg^?1; total inorganic P (P_it) accounted for 20 to 81 % of P_t; and enzymatically hydrolysable P (P_et) accounted for 5 to 26 % of P_t. Liquid–solid separation tended to concentrate the manure P in the liquid fractions. In contrast, anaerobic digestion did not affect the manure P distribution compared with the undigested raw manure from the same system. No differences in P distribution were found for the compost bedded pack manure. In the soil incubation study, manure and fertilizer were applied at 40 mg total P kg^?1. Separated liquid manure from two systems tended to increase STP more than the separated solid manures from the same systems. Although anaerobic digestion modified some of the physical and chemical properties of the treated manures, it did not clearly impact how digested manure increased STP compared with the raw manures. Overall, the increase in STP after treated manure application was found to be a function of soil clay content and manure P_it?+?P_et applied.     

长期施肥对红壤双季稻冬闲田春季杂草群落的影响

利用始于1982年的红壤双季稻田长期施肥定位试验,于2012年采用田间调查法研究了在无机肥(化肥NPK)与有机肥(M)氮磷钾养分等量条件下,长期施用有机肥、无机化肥和有机肥无机肥配施模式下红壤双季稻冬闲田春季杂草生物量及群落密度和群落多样性的变化。结果表明:有机肥无机肥配施改变了优势杂草种类,增加了杂草总密度和总生物量。化肥氮钾配施有机肥(NKM)处理的杂草种类数量最多,化肥氮磷配施有机肥(NPM)处理的最少。施肥处理中,M处理的杂草群落多样性指数、均匀度指数和优势度指数均最高,分别为1.118 6、0.732 3和0.629 7;其杂草总密度最低,为297.0株?0.25m?2。NPK处理的杂草总生物量最低,为58.0 g?0.25m?2。NPM处理的杂草群落多样性指数值、均匀度及优势度指数值均显著低于其他处理;其杂草总密度和杂草总生物量均最高,分别为539.7株?0.25m?2和109.5 g?0.25m?2;其优势杂草日本看麦娘的密度为428.0株?0.25m?2,相对密度为79.31%,明显高于其他处理优势杂草的密度和相对密度。春季杂草总干物质量与土壤碱解氮正相关(相关系数为0.703),与土壤p H负相关(相关系数为0.697),相关性不显著;与土壤有效磷显著正相关(相关系数为0.758*)。长期不同施肥模式下红壤稻田磷素是导致田间春季杂草群落特征变化的主要因素,通过改变土壤有效磷和碱解氮含量及土壤p H,能有效调控红壤双季稻冬闲田春季杂草生物量及群落密度和生物多样性。     

菜场夏闲田一季中晚稻耕作栽培模式研究

2006年5~9月在广东省博罗县园洲镇的会达菜场和鸿霖菜场, 以“黄华占”水稻为试材, 进行一季中晚稻不同耕作方法和不同种植方式的研究, 探索稻菜轮作系统的水稻种植省工节本、节能减排与循环利用技术措施。结果表明: 耕作方法对水稻产量无显著影响, 种植方式中抛秧和插植的产量差异不显著, 但比直播显著或极显著增产。耕作方法中, 常耕的有效穗数较多、穗粒数较少, 免耕、免耕旱管的有效穗数较少、穗粒数较多; 不同耕作方法的结实率和千粒重无显著差异。种植方式中, 直播的有效穗数最多、穗粒数最少、千粒重最轻, 产量最低; 抛秧穗数适宜、穗粒数和群体颖花数较多, 千粒重较大, 产量最高; 插植的群体颖花数与直播相近, 籽粒充实, 产量水平居中。耕作方法和种植方式对产量构成因素有不同的影响, 其中对千粒重影响最大, 每穗总粒数次之, 结实率和有效穗数相对比较稳定。结果表明, 一季中晚稻采用常耕、免耕和免耕旱管均可行, 采用抛秧或插植的效果比直播好。     

化学和黏土矿物钝化剂对牛粪秸秆堆肥磷形态转化的影响

盲目施用粪肥导致农田土壤磷素(P)积累和产生的面源污染等环境风险已引起人们的重视。该文通过在牛粪秸秆堆肥过程中,添加质量分数2.5%的化学物质或黏土矿物2类磷素钝化剂,研究其对磷素形态转化的影响。结果显示,和对照相比,添加氧化钙、氧化镁、硫酸亚铁和明矾可明显降低堆肥产品中磷素的活性,水溶性磷(water extract phosphorus,WEP)占总磷(totalphosphorus,TP)百分比分别为:38.0%、60.2%、58.8%、28.9%;添加蛭石和沸石使堆肥产品中WEP占TP百分比分别下降11.7%、17.3%。第35天堆肥样品的Hedley磷分组结果显示,添加氧化钙和氧化镁主要促进了H_2O-Pi向更稳定态的NaHCO_3-Pi、HCl-P(Pi和Po)、残余态-P转化;添加硫酸亚铁和明矾主要促进了H_2O-Pi向更稳定态的NaOH-P(Pi和Po)、残余态-P转化。添加黏土矿物钝化剂均略微促进了不稳定态磷H_2O-Pi和NaHCO_3-Pi向稳定态磷HCl-Pi转化。堆肥结束时添加MgO明显提高了堆体的pH值,其他处理均对pH值影响较小。综合来看硫酸亚铁、明矾、沸石和蛭石依次为较好的磷素钝化材料。     

施氮量对潮土区冬小麦-夏玉米轮作农田氮磷淋溶的影响

潮土是我国华北地区主要土壤类型之一,潮土区是我国冬小麦-夏玉米作物的主要产区,研究不同施氮量潮土氮磷淋溶特征对于指导区域农田面源污染防控具有重要意义。本研究设置3个施肥处理,即传统施氮(CON)、优化施氮(OPT)和优化再减氮(OPTJ),利用田间渗漏池法,研究潮土冬小麦-夏玉米轮作农田硝态氮及总磷淋溶特征。结果表明:2016—2018年,冬小麦-夏玉米轮作周年不同施肥处理90cm土层年淋溶水量79.0～102.5 mm,不同淋溶事件间土壤淋溶液硝态氮浓度波动较大, CON、OPT和OPTJ处理单次淋溶事件硝态氮浓度分别为18.9～208.7(平均为72.7) mg·L~(-1)、9.0～99.2 (平均为33.8) mg·L~(-1)、4.7～55.5 (平均为15.4) mg·L~(-1)。本研究区域冬小麦-夏玉米轮作模式的氮素淋溶风险较高,磷素淋溶风险较低。传统施氮处理(CON)下农田硝态氮的平均淋溶量和表观淋失系数分别为66.4 kg·hm~(-2)和10.3%,而总磷(TP)为0.06 kg·hm~(-2)和0.04%。氮肥减施会显著降低氮素淋失,OPT和OPTJ处理的氮素淋溶减排率可达56.3%和78.9%。两个年度CON、OPT和OPTJ处理硝态氮平均表观淋失系数分别为10.3%、6.2%和4.9%,随着施氮量的增加,硝态氮淋失系数动态增加。氮淋溶具有较大的年际变化,降雨量高的2018年比降雨少的2017年硝态氮淋溶量多57.0%。两个年度CON、OPT和OPTJ处理总磷平均淋溶量分别为0.06 kg·hm~(-2)、0.06 kg·hm~(-2)和0.08 kg·hm~(-2)。适量减施氮肥会增加作物产量, OPT处理的作物产量是CON处理的1.08倍。然而,过量减施则会带来减产风险, OPTJ处理氮肥减施56%,作物产量比CON处理降低2.0%～8.1%。总之,潮土区农田硝态氮淋溶风险较大,适量减施氮肥能够在保证作物产量的基础上显著降低氮素淋失损失。     

Retarded leaching of nitrate measured in monolith lysimeters in south-east Nigeria

At Onne in South-east Nigeria, drainage water was collected from four monolith lysimeters and analysed for nitrate. The lysimeters contained an acid sandy loam. At the start of the first rainy season two lysimeters received urea labelled with ¹⁵NO₃^– and two received no nitrogen fertilizer; all four were uncropped in the first year.
The peak concentrations of ¹⁵NO₃^– and of unlabelled (soil) NO₃^– were found after 2.5 pore volumes of water had passed through the lysimeters. Using the same soil in the laboratory after fine sieving, the peak concentration of tritiated water was found at 1 pore volume whereas nitrate leaching was retarded. The pattern of nitrate leaching was well described by miscible and immiscible models which included an adsorption coefficient for nitrate. Over the 2 years 81.4% of the ¹⁵N added at the start of the first rainy season was recovered in the drainage water.     

施用粪肥对农田土壤磷素累积和饱和度增加速率的影响

针对施用粪肥导致的我国集约化种养区域农田土壤磷素高量累积和高环境风险问题,利用长期定位试验定量分析了施用粪肥对农田土壤磷素累积和磷饱和度（DPS, degree of P saturation）增加速率（每年1 kg P·hm-2磷素盈余所导致的土壤磷素含量或DPS变化量）的影响。结果表明：连续22年过量磷素投入明显提高了土壤磷素含量和DPS,0~20 cm土层土壤磷素累积、DPS增加与磷素盈余均存在明显的线性相关性。与单施化肥相比,施用粪肥对土壤全磷的累积速率影响不大,但是明显提高了土壤Olsen-P累积和DPS增加速率。施用粪肥下,每年1 kg P·hm-2的磷盈余所导致的0~20 cm土层土壤Olsen-P、CaCl2-P累积和DPS增加量分别为0.071 mg P·kg-1（r=0.608, P=0.029）、0.003 mg P·kg-1（r=0.528, P=0.066）和0.036%（r=0.863,P=0.002）,分别为不施粪肥的3.3、6.0倍和1.2倍。土壤DPS变化与磷含量变化之间也存在明显的线性关系,0~20 cm土层土壤每年全磷、Olsen-P和CaCl2-P含量增加1 mg P·kg-1所导致的土壤DPS增加值分别为0.13%、0.42%和7.78%。20~40 cm土层土壤磷素累积、DPS增加与磷素盈余之间的线性相关性均较差,但与0~20 cm土层相比,施用粪肥和不施粪肥之间累积速率的差异性有增大的趋势,说明施用粪肥促进了磷素向下层土壤的移动。施用粪肥加速了土壤有效磷累积和DPS增加,进而提高了土壤中磷素损失风险,合理施用粪肥是控制集约化种养区域农田磷面源污染的关键。     

Leaching and balances of phosphorus and other nutrients in lysimeters after application of organic manures or fertilizers

Abstract. A long-term lysimeter experiment with undisturbed monoliths studied leaching behaviour and balances of phosphorus (P), potassium (K) and nitrogen (N) during a seven year crop rotation on four types of soil receiving inorganic fertilizers, manure and grass compost respectively. It was shown that application of manure did not lead to any direct change in nutrient leaching, unlike the application of fertilizers to soils of normal fertility. However, soil type considerably affected the nutrient concentrations in the drainage water.
Manure applied in amounts equal to the maximum animal density allowed by Swedish legislation slightly oversupplied P and N (0.5–3.5 and 18–38 kg ha⁻¹ y⁻¹ respectively) compared to the crop requirement and leaching losses for most of the soils. The relationship between lactate-soluble P in the topsoil and the concentrations of dissolved P in the drainage water was very strong. However the strength of this relationship was dependent on just one or two soils. P losses from a fertile sandy soil were large (1–11 kg ha⁻¹ y⁻¹) throughout the crop rotation and average crop removal (13 kg ha⁻¹ y⁻¹) plus the leaching losses were not balanced (average deficit 3–6 kg ha⁻¹ y⁻¹) by the addition of fertilizer, manure or grass compost. No decreasing trend was found in the P losses during seven years. However, the K deficit (average 26 kg ha⁻¹ y⁻¹) led to a significant reduction in the leaching trend from this soil. The other soils that had a smaller K deficit showed no significant reduction in the leaching of K.     

施氮水平与模拟降雨pH值对玉米冠层NO3--N淋失的影响

为探明降雨特别是酸雨对玉米冠层氮素淋失的影响,以盆栽试验春玉米为指示作物,采用自制人工降雨器进行模拟降雨,研究施氮与不施氮（对照）条件下玉米冠层NO3--N淋失动态、数量及随生育期和降雨酸度的变化规律。结果表明,中性和弱酸性降雨淋洗,NO3--N淋失量主要由冠层氮素含量决定,而强酸雨淋洗,NO3--N淋失量受降雨pH值和冠层氮素含量共同影响。各生育期玉米冠层NO3--N淋失量随降雨pH值降低变化规律不一,生育前期降雨pH值对冠层NO3--N淋失影响较生育后期显著,在研究降雨酸度对玉米冠层NO3--N淋失的影响时,必须考虑生育期。相同pH值模拟降雨条件下,玉米冠层NO3--N淋失量随生育期推进逐渐降低：11叶期>吐丝期>灌浆期,生育前期显著高于中后期。玉米冠层NO3--N淋失量不仅与介质施氮有关,同时受降雨pH值影响,2因素在不同生育期对NO3--N淋失贡献大小有所不同,但总体看,植物体氮素丰富程度是影响冠层NO3--N淋失的主要因素。各生育期玉米冠层均存在一定数量的NO3--N淋失,尤以生育前期为甚,说明在研究农田生态系统氮素流量和冠层氮素损失时,冠层氮素淋失应予以考虑。     

Effects of repeated manure and fertilizer phosphorus additions on soil phosphorus dynamics under a soybean-wheat rotation

 Soil P availability and efficiency of applied P may be improved through an understanding of soil P dynamics in relation to management practices in a cropping system. Our objectives in this study were to evaluate changes in plant-available (Olsen) P and in different inorganic P (P_i) and organic P (P₀) fractions in soil as related to repeated additions of manure and fertilizer P under a soybean-wheat rotation. A field experiment on a Typic Haplustert was conducted from 1992 to 1995 wherein the annual treatments included four rates of fertilizer P (0, 11, 22 and 44 kg ha^–1 applied to both soybean and wheat) in the absence and presence of 16 t ha^–1 of manure (applied to soybean only). With regular application of fertilizer P to each crop the level of Olsen P increased significantly and linearly through the years in both manured and unmanured plots. The mean P balance required to raise Olsen P by 1 mg kg^–1 was 17.9 kg ha^–1 of fertilizer P in unmanured plots and 5.6 kg ha^–1 of manure plus fertilizer P in manured plots. The relative sizes of labile [NaHCO₃-extractable P_i (NaHCO₃-P_i) and NaHCO₃-extractable P₀ (NaHCO₃-P₀)], moderately labile [NaOH-extractable P_i (NaOH-P_i) and NaOH-extractable P₀ (NaOH-P₀)] and stable [HCl-extractable P (HCl-P) and H₂SO₄/H₂O₂-extractable P (resisual-P)] P pools were in a 1 : 2.9 : 7.6 ratio. Application of fertilizer P and manure significantly increased NaHCO₃-P_i and -P₀ and NaOH-P_i, and -P₀ fractions and also total P. However, HCl-P and residual-P were not affected. The changes in NaHCO₃-P_i, NaOH-P_i and NaOH-P₀ fractions were significantly correlated with the apparent P balance and were thought to represent biologically dynamic soil P and act as major sources and sinks of plant-available P. Received: 23 October 1997     

滇池流域人工模拟降雨条件下农田施用有机肥对磷素流失的影响

应用田间原位人工模拟降雨的方法,在滇池流域不同作物类型农田上研究了有机肥（猪粪）不同用量水平对农田磷素流失的影响。结果显示,随着有机肥（猪粪）施用量的增加,农田流失液中各形态磷素的平均浓度提高,两者间呈显著正相关,相关系数均达到0..9以上。径流方式下,颗粒态磷是主要流失形态;渗漏方式下,有机肥用量水平低时颗粒态磷是主要流失形态,有机肥用量达到中等至较高水平时水溶性是流失的主要形态。同一有机肥用量水平下,不同作物类型农田流失液中各形态磷素的平均浓度均表现为:蔬菜田花卉田粮田。     

不同施磷量对蔬菜地土壤硝态氮淋失的影响

【目的】在两种蔬菜地土壤上研究不同磷肥施用量对土壤硝态氮淋失的影响,为武汉城郊蔬菜合理施用磷肥和安全生产提供理论依据。【方法】利用大型原状土柱渗漏装置,2种实验土壤(粉质粘土和粉质粘壤土)均为武汉城郊典型蔬菜土壤,分别采自华中农业大学校内蔬菜基地和湖北新洲。试验期间共种植了四种蔬菜(小白菜、 辣椒、 苋菜及萝卜)。试验设置了4个P2O5水平处理(0、 125、 250、 375 kg/hm2),氮肥施用量均为N 750 kg/hm2,钾肥施用量均为K2O 500 kg/hm2。试验期间年降雨量为1043.0 mm,各土柱总灌溉量为120.1 L。秋冬季每15天、 春夏季每10天收集一次淋洗液,另外根据天气和降雨情况适当调节,每次收集淋洗液时记录淋洗液体积并测定淋洗液硝态氮浓度。在每季蔬菜生长成熟后将蔬菜收获称重,烘干后测定蔬菜中氮素含量。【结果】1)与不施磷肥相比,施用磷肥显著增加了两种土壤上小白菜、 苋菜、 萝卜产量以及四季蔬菜总产量,其产量随磷肥施用量增加而增加或显著增加,在磷肥施用量最大时产量达到最大值。粉质粘土上的产量显著低于粉质粘壤土上的产量,粉质粘壤土总产量约是粉质粘土总产量的1.63~2.36倍。2)施用磷肥显著增加了小白菜、 苋菜氮素吸收累积量以及四季蔬菜总吸收累积量,且两种土壤上总氮素吸收累积量均在磷肥施用量最大时达到最大值。粉质粘壤土上氮素总吸收累计量显著高于粉质粘土上氮素总吸收累积量。3)磷肥水平对土壤总渗漏液体积并无显著影响(粉质粘壤土P2O5 125 kg/hm2处理除外),粉质粘土渗漏水量显著大于粉质粘壤土。4)施用磷肥降低或显著降低土壤淋失液硝态氮浓度(粉质粘土苋菜季除外),随着磷肥施用量的增加硝态氮淋失浓度不断降低,4季蔬菜平均淋失浓度最大降低了38.6%(粉质粘土)和28.8%(粉质粘壤土)。5)磷肥施用显著降低了两种土壤上硝态氮淋失量(苋菜季除外),且在粉质粘土上随着磷肥施用量的增加硝态氮淋失量不断降低,而在粉质粘壤土上硝态氮淋失量先降低后上升。粉质粘土硝态氮淋失量显著大于粉质粘壤土,磷肥施用降低硝态氮淋失量分别达到达26.4%~33.7%和23.5%~39.9%。【结论】磷肥施用增加了蔬菜产量和作物氮素吸收累积量,从而显著降低了两种土壤上硝态氮的淋失; 土壤质地对硝态氮淋失有较大影响,质地较轻的粉质粘壤土硝态氮淋失显著小于质地较重的粉质粘土; 粉质粘壤土上施用P2O5量为250 kg/hm2时能提高产量同时减少硝态氮淋失,而粉质粘土上施用P2O5量为375 kg/hm2时能获得较大产量和较少硝态氮淋失量。     

施用有机肥对土壤肥力的影响

在潮棕壤上进行了5年的定位试验,研究不同有机肥用量对作物产量和土壤肥力的影响。结果表明,施用有机肥处理与对照处理相比,施用有机肥有明显的增产和稳产作用。不施肥处理,除土壤全钾以外,土壤其他各项养分指标（C、N、P）均有所下降;施用有机肥能显著提高速效P、K养分含量和有机碳及全磷含量。5年时间,低量有机肥处理土壤碱解氮含量下降了9.19mg/kg,说明低量有机肥并不能保证土壤氮的供给;中量有机肥处理土壤碱解氮含量略有上升,土壤全氮收支基本平衡;高量有机肥处理土壤碱解氮含量有明显增加,土壤全氮也有较大程度的盈余。     

水稻季施肥对后季绿肥物质养分积累的影响

田间试验条件下,研究水稻季不同氮、磷、钾肥用量对后季绿肥物质养分积累的影响,为水稻-紫云英轮作条件下适宜化肥用量的确定提供依据。结果表明,水稻季施氮、磷、钾肥处理的绿肥鲜草产量分别较不施氮、磷、钾肥处理增加27.9% ~ 40.9%、12.6% ~ 37.2%、21.4% ~ 46.2%。水稻季不同氮肥处理比较,施氮处理的氮积累量较不施氮处理增加48.8% ~ 62.3%,氮肥（N）用量为142.4 kg/hm2时,绿肥碳、氮、钾积累量最高,氮肥用量为71.2 kg/hm2时,绿肥磷积累量最高。水稻季不同磷肥处理比较,施磷处理的绿肥磷积累量较不施磷处理增加33.0% ~ 78.3%,磷肥（P）用量为49.1 kg/hm2时绿肥的碳、氮、磷、钾积累量均最高。水稻季施钾处理的绿肥钾积累量较不施钾处理增加22.2% ~ 44.8%,水稻季钾肥（K）用量为67.5 kg/hm2和101.2 kg/hm2时,绿肥的碳、氮、磷、钾积累量较高,且两处理间相差较小。本试验条件下,水稻季氮、磷、钾用量分别为142.4、49.1、67.5（或101.2）kg/hm2时,绿肥的产量及碳、氮、磷、钾积累量最高,分别为15 833 kg/hm2和929.2、44.6、5.8、45.9 kg/hm2。