Weed growth and crop yield responses to tillage and mulching under different crop rotation sequences in semi‐arid conditions

Conservation agriculture (CA) is thought to reduce weed pressure from the third year of adoption, when recommended practices are followed. Weed growth and crop yield were assessed during the third and fourth year of maize–cowpea–sorghum rotation, second and third year of maize–cowpea rotation and first and second year of maize monocropping on a clay loam soil at Matopos Research Station (annual rainfall, 573 mm) following recommended CA management practices. Each experiment had a split‐plot randomized complete block design with mouldboard plough (CONV), minimum tillage (MT) with ripper tine and planting basins as main‐plot factor and maize residue mulch rate (0, 2 and 4 t/ha) as a subplot factor, with threefold replication. All subplots were surface mulched and weeded by hoe at the same time. We hypothesized that under MT weed growth would be considerable with maize monocropping but from year 3 of CA, weed growth would decrease and crop yield increase relative to values from unmulched CONV. Minimum tillage increased weed growth in 2nd year of maize monocropping. Under the maize–cowpea rotation, the considerable weed growth in planting basins was likely due to the large intrarow spacing and poor light competiveness of the cowpea variety. Mulch contributed to weed growth being suppressed by up to 36% under CA in the maize–cowpea–sorghum rotation relative to unmulched CONV. When planted on the same date, crop yield did not differ between CA and unmulched CONV. Maize–cowpea–sorghum rotation grain yield (3143 kg/ha) was double that under monocropping , probably due to improvements in soil physical and chemical conditions.     

Effects of tillage systems on soil physical properties,root distribution and maize yield on a Colombian acid-savanna Oxisol

Abstract

Tillage systems may affect many soil properties, which in turn may alter the soil environment and consequently impact on root growth and distribution, and crop yield. In 1993, a long-term field experiment on sustainable crop rotation and ley farming systems was initiated on a Colombian acid-savanna oxisol to test the effects of grain legumes, green manures, intercrops and leys as possible components that could increase the stability of systems involving annual crops. In the present study, five agropastoral treatments (maize monoculture, maize-soybean rotation, maize-soybean green manure rotation, native savanna, maize-agropastoral rotation) under two tillage systems (no tillage and minimum tillage) were investigated. Lower bulk density and higher total porosity for all treatments and soil layers were found in no-tillage compared to the minimum tillage system. Between the two tillage systems, significantly higher maize grain yields (p<0.1) were obtained under no-tillage agropastoral treatments compared to the same treatments under minimum tillage. Maize yields on native savanna soils were markedly lower than in the rest of the treatments, indicating the need for improved soil conditions in subsoil layers for root growth of maize.     

低土壤肥力下秸秆还田和施钾对作物产量及土壤钾素平衡的影响

为了研究我国华北平原低肥力土壤条件下秸秆还田和施钾肥对作物产量和钾素平衡的影响,于2008年10月～2011年10月在中国农业科学院高新技术园区国家测土施肥中心实验室试验基地（河北省廊坊市）,通过3年6季的定位试验,比较了施钾与秸秆还田的增产效应、钾素吸收利用和作物土壤系统的钾素平衡状况。结果表明:在氮、磷肥充足的情况下,施用钾肥（NPK）、秸秆还田（NP+St）和秸秆还田配施钾肥（NPK+St）,均有明显的增产效应,表现为NPK+StNPKNP+StNP;不同施钾措施在夏玉米上的增产效果优于冬小麦;同一作物秸秆还田结合施钾肥的增产效果最好,降低了年度间的产量变异系数,在获得高产的同时,年际间产量稳定,有利于稳产;施钾肥和秸秆还田可显著提高小麦和玉米的钾素吸收总量; NPK+St、NPK、NP+St处理的钾素表观平衡系数分别为1.26,0.42,0.92。秸秆还田和施钾肥有利于钾素的收支平衡,减轻作物对土壤钾素的消耗,缓解土壤钾素肥力下降的程度,可维持土壤钾素肥力的稳定。     

低土壤肥力下施钾和秸秆还田对作物产量及土壤钾素平衡的影响

为了研究我国华北平原低肥力土壤条件下秸秆还田和施钾肥对作物产量和钾素平衡的影响,于2008年10月～2011年10月在中国农业科学院高新技术园区国家测土施肥中心实验室试验基地(河北省廊坊市),通过3年6季的定位试验,比较了施钾与秸秆还田的增产效应、钾素吸收利用和作物-土壤系统的钾素平衡状况。结果表明:在氮、磷肥充足的情况下,施用钾肥(NPK)、秸秆还田(NP+St)和秸秆还田配施钾肥(NPK+St),均有明显的增产效应,表现为NPK+St>NPK>NP+St>NP;不同施钾措施在夏玉米上的增产效果优于冬小麦;同一作物秸秆还田结合施钾肥的增产效果最好,降低了年度间的产量变异系数,在获得高产的同时,年际间产量稳定,有利于稳产;施钾肥和秸秆还田可显著提高小麦和玉米的钾素吸收总量;NPK+St、NPK、NP+St处理的钾素表观平衡系数分别为1.26、0.42、0.92。秸秆还田和施钾肥有利于钾素的收支平衡,减轻作物对土壤钾素的消耗,缓解土壤钾素肥力下降的程度,可维持土壤钾素肥力的稳定。     

下辽河平原水肥交互作用及对玉米产量的影响

以沈阳生态试验站一组持续16年的长期定位试验为平台,研究了不同降水年景作物对施肥的增产反应及水分对肥料增产的促进作用,估算了下辽河平原地区水肥交互作用对作物增产的贡献。结果表明,该地区玉米蒸散耗水与其生育期内降水之间关系密切,且不同的施肥处理对玉米消耗水分量影响不大。过少或过多的降水均会降低玉米产量。在高肥力水平下平水年(降水400～550 mm)玉米产量最高,水肥交互作用对作物增产的贡献亦达最大,可占总增产量的44.9%。     

土壤地力和长期施肥对潮土区小麦和玉米产量演变趋势的影响

为潮土区合理施肥管理提供依据,对32个长期定位点、24年（1987～2010）不施肥和化肥配施秸秆（农民常规施肥）处理的小麦和玉米产量及其与土壤地力和施肥量间的关系进行了分析。结果表明:潮土区土壤地力对小麦和玉米产量的平均贡献率分别为51.4%和54.0%,变异系数分别为39.0%和41.2%。不施肥处理小麦和玉米产量每年分别下降4.1 kg/hm2和96.6 kg/hm2;常规施肥处理的小麦和玉米每年分别增产61.5 kg/hm2和26.8 kg/hm2。施化肥量与作物增产量（常规施肥产量－不施肥产量）呈显著正相关。通过通径分析进一步证明,施氮量对小麦产量具有显著直接作用。同时,磷肥对提高小麦和玉米的产量具有重要作用。总之,在农民习惯耕作施肥管理水平下,潮土区不施肥处理的产量下降缓慢（含品种对产量的贡献）,常规施肥区产量表现出缓慢增加的趋势。     

长期施肥下我国灌淤土粮食产量和土壤养分的变化

【目的】 灌淤土是我国西北地区重要的粮食和经济作物土壤。了解灌淤土上作物产量的变化,及其对长期施肥的响应,以及灌淤土生产力的变化与其氮磷钾含量的关系,为西北地区作物增产和灌淤土培肥与可持续利用提供理论依据。 【方法】 1988到2004年间,在宁夏银川市、吴忠市、石嘴山市和新疆和田市典型灌淤土区域陆续建立了7个国家耕地质量监测点。2016年,利用时间趋势分析法,探讨了作物产量随时间的变化趋势,分析了长期不施肥和常规施肥条件下,玉米、小麦和水稻产量、产量变异系数、可持续性指数、增产率及地力贡献指数的变化特征,并进一步探讨了增产率与土壤养分的关系。 【结果】 灌淤土上小麦产量随时间呈现递增的趋势,在2004年达到最高 (7.58 t/hm2),之后保持稳定,2016年约为初始年产量的3倍;玉米产量随时间一直呈递增趋势,2016年平均产量为9.8 t/hm2,约为初始年的两倍;水稻产量近年来变化不大。与不施肥相比,常规施肥下小麦、玉米 (28年间) 和水稻 (8年间) 分别平均增产3.43倍、3.20倍和1.21倍,产量可持续性指数分别提高了18.8%、148%和13.9%。监测以来,小麦和玉米农田的地力贡献指数略有下降,但变化不显著。水田的地力贡献指数以每年0.0125的速率增加。28年间,常规施肥使土壤全氮含量从0.4 g/kg提高到1.1 g/kg,有效磷和速效钾含量变化不大。小麦与玉米的增产率与土壤全氮含量呈显著直线正相关关系,小麦、玉米和水稻的平均氮肥农学效率分别为9.8、16.8和27.4 kg/kg。 【结论】 灌淤土上常规施肥 (主要是氮肥)有效提高了玉米、小麦和水稻的产量。土壤全氮含量呈增加趋势,有效磷和有效钾含量基本平稳。土壤肥力对玉米和小麦产量的贡献呈下降趋势,对水稻产量的贡献高且平稳。因此,灌淤土应在合理施用氮肥的同时,注重采取提升地力,实现作物的高产和高效。      

Mulch effect on successive crop yields and soil carbon in Tonga

Intensification of crop production in Tonga has resulted in a move to mechanical soil preparation, often with a rotary hoe, and a consequent loss in both chemical physical fertility. An experiment was conducted on a clay loam soil (Typic Argiudoll) on the Forestry Vaini Research Station, Tongatapu Island, Tonga, to investigate the effect of a once‐off application of mulch on yield and quality of watermelon, maize and capsicum grown in rotation over a 1‐yr period. The treatments applied were a nonmulched control, transparent plastic and 200‐mm‐thick applications of locally available coconut sawdust, guinea grass and mature coconut fronds. The fresh fruit yield of watermelon in all the mulch treatments was 7.3–18.1% higher than in the nonmulched control. There was no significant effect of thick vegetative mulch on maize grain dry matter yield; however, the maize yield was significantly lower in the transparent plastic mulch than in the other treatments. The capsicum marketable fruit yield in the following crop was increased by 49–73% in all the vegetative mulch treatments compared to the non‐mulched control. The higher crop yields with the vegetative mulch were attributed to the measured lower soil temperatures and higher soil moisture in these treatments. There was no effect of mulch on soil total N (TN), but soil total C (TC), soil labile C (LC) and the carbon management index (CMI) were increased.     

长期保护性耕作对土壤有机碳和玉米产量及水分利用的影响

【目的】通过研究保护性耕作对旱地春玉米土壤有机碳(SOC)、产量及水分利用的影响,分析保护性耕作的增产机制,为旱作农田耕作技术应用提供理论和技术支持。【方法】采用2003~2013年连续11年的田间定位试验,设传统耕作(CT)、少耕(RT)和免耕(NT)3种耕作措施,分析土壤0-20 cm和20-40 cm土层有机碳含量、土壤0-20 cm含水量、作物耗水量、玉米产量和水分利用效率的年际变化和耕作处理间的差异,并对玉米产量与影响因素的相关性进行分析。【结果】1)保护性耕作能有效提高土壤有机碳含量,少耕、免耕处理0-20 cm土层有机碳含量11年平均值较传统耕作分别提高了11.2%和3.4%;至2013年少耕、免耕20-40 cm土层有机碳含量分别较传统耕作增加了5.53和3.29 g/kg;土壤0-20 cm有机碳储量净增加速率分别为C 0.365和0.754t/(hm2·a)。2)保护性耕作具有明显的增产效果,少耕产量最高,增产效果最好2003~2013年均产量为5.83t/hm~2,较传统耕作提高了14.7%;免耕次之,年均产量为5.39 t/hm~2,较传统耕作增产6.1%。3)各耕作处理玉米产量与土壤0-20 cm土层含水量之间存在显著的二次方程关系,与作物耗水量之间具有显著的乘幂方程关系。4)保护性耕作可以增加土壤水分减少玉米生育期内的耗水量,提高水分利用效率,其中免耕土壤0-20 cm土层水分含量最高2003-2013年平均含水量为15.2%,较传统耕作和少耕提高了1.90和1.66个百分点,且生育期耗水量最少2003~2013年均耗水量为403.5 mm,较传统耕作和少耕减少了16.1 mm和7.6 mm;少耕、免耕的水分利用效率较传统耕作分别提高了16.1%和10.2%,降水利用效率较传统耕作提高13.9%和5.8%。【结论】长期保护性耕作可以有效地提高土壤有机碳含量、增加土壤水分、减少作物耗水量,从而显著提高了玉米产量和水分利用效率,3种耕作措施中以少耕效果最好,免耕次之在旱作农田推广少、免耕保护性耕作措施是一种增产、节水的有效途径。     

Applications of reduced tillage in hills of central Nepal

Conventional tillage practices on steep and fragile landscape of Himalayan hills result in significant loss of topsoil during rainy season. Soil erosion in Nepal mid-hills is the most critical during pre-monsoon season. Many reviews argue that reduced tillage could be an option to tackle this problem. However, very few field experiments to evaluate reduced tillage systems have to date been conducted in this region. Thus, a field experiment was initiated in factorial randomized complete block design on acidic sandy loam soil (Lithic Dystochrept) during the summer season of 2001 at Kathmandu University (1500 masl) to assess the effects of tillage and cropping patterns on soil and nutrient losses, crop yield and soil fertility. Two main treatments viz. conventional and reduced till, and two sub-treatments viz. sole maize (Zea mays) and maize + soybean (Glycine max) were considered. Soil organic carbon (OC), total nitrogen (N), plant available phosphorus (P) and exchangeable potassium (K) were determined for the original soil and eroded sediment using standard methods. Two years of data indicated annual soil and nutrient losses to be significantly lowered by reduced till as compared to conventional till. Total annual soil loss from conventional and reduced till was 16.6 and 11.1 Mg/ha, respectively. Similarly, annual nutrient losses associated with the eroded sediment were 188 kg OC/ha, 18.8 kg N/ha, <1 kg P/ha and 3.8 kg K/ha for conventional till and 126 kg OC/ha, 11.8 kg N/ha, <1 kg P/ha and 2.4 kg K/ha for reduced till. Soil OC and N losses were significantly higher in conventional till and this may be one of the major causes of fertility depletion in the Nepalese hills. Soil chemical properties did not differ due to tillage and cropping systems; however, over years pH, N and P were increased irrespective of treatments. Although treatments were at par for maize grain yield, conventional till + soybean produced highest grain yield (4.0 Mg/ha) followed by reduced till + soybean (3.9 Mg/ha) and conventional till sole maize (3.8 Mg/ha). Mixed cropping of legumes and maize do not help conserve soil and nutrient loss in hills of central Nepal. Thus, reduced till could be a viable option for minimizing soil and nutrient losses without sacrificing economic yields in central hills of Nepal.     

耕作方式和秸秆还田对砂姜黑土碳库及玉米小麦产量的影响

长期秸秆还田免耕覆盖措施导致沿淮区域砂姜黑土耕层变浅、下表层(10～30 cm)容重增加、土壤养分不均衡等问题凸显,限制了小麦-玉米周年生产力的提高。耕作和秸秆还田措施合理的搭配组合是解决这一问题的有效方法。通过8年的小麦-玉米一年两熟田间试验,设置4个处理:1)玉米季免耕-小麦季免耕秸秆不还田(N);2)玉米季深耕-小麦季深耕秸秆不还田(D);3)玉米季秸秆免耕覆盖还田+小麦秸秆免耕覆盖还田(NS);4)玉米季秸秆免耕覆盖还田+小麦季秸秆深耕还田(DS)。通过分析作物收获后不同土壤深度(0～60 cm)总有机碳(TOC)、颗粒态碳(POC)、微生物生物量碳(MBC)、易氧化态碳(KMnO4-C)、可溶性有机碳(DOC)和土壤碳库管理指数(CPMI),并结合小麦-玉米的周年产量变化,以期获得培肥砂姜黑土的最佳模式。研究结果表明:1)相对于长期免耕措施(N),DS处理能够提高0～30 cm土层TOC、POC、MBC、KMnO4-C等组分含量和CPMI;而NS措施仅提高土壤表层(0～10 cm)TOC、活性有机碳组分含量和CPMI;2)DS处理显著提升了小麦-玉米的周年生产力,其麦玉的周年产量均值分别比N、D和NS处理高出14.7%、12.9%和8.5%;3)MBC和KMnO4-C对于耕作和秸秆还田措施都是较为敏感指示因子。总的来说,玉米季小麦秸秆覆盖还田+小麦季玉米秸秆深耕还田(DS)是改善沿淮地区砂姜黑土土壤碳库、提高小麦-玉米周年产量的一种有效农田管理模式。     

柠条秸秆和地膜覆盖对土壤水分和玉米产量的影响

为了探讨北方农牧交错带不同保墒措施下旱地玉米的土壤水分特征及其对产量的影响,以甘农118为试验材料,监测了单膜(SFP)、双膜(DFP)、柠条秸秆沟埋(CPDP)和裸地(CK)4种不同处理下0~100 cm土壤水分季节变化、垂直变化及年际变化,测定了玉米产量和水分利用效率。结果表明:SFP和DFP处理明显改善0~40 cm土层土壤体积含水率,较CK处理保墒效果提高35.65%~47.91%,但随着玉米生育期的推进,由于玉米生长耗水和土壤蒸发作用,建植后土壤体积含水率均接近或低于萎蔫系数(7.20%)。连续2 a种植玉米4种处理土壤贮水量均有不同程度的减少,CPDP和CK处理土壤贮水量分别减少了68.42和68.07 mm,其次为SFP(53.49 mm),DFP减少最小(48.98 mm),说明研究区内玉米生长需要消耗大量土壤水分。SFP和DFP能够增加玉米对降雨和土壤水的利用,不同年份产量水分利用效率较CK处理分别提高12.55%~35.71%和25.11%~54.70%。SFP和DFP耗水量、产量和水分利用效率均无显著差异(P0.05),因此建议在研究区种植玉米时可以采取SFP措施,而CPDP耗水量较高、产量和水分利用效率相对较低,不宜采取此种保墒措施。     

Soil C and N dynamics and maize (Zea may L.) yield as affected by cropping systems and residue management in North-western Pakistan

This paper presents the results of irrigated rotation experiment, conducted in the North West Frontier Province (NWFP), Pakistan, during 1999–2002 to evaluate effects of residues retention, fertilizer N and legumes in crop rotation on yield of maize (Zea mays L.) and soil organic fertility. Chickpea (Cicer arietinum L) and wheat (Triticum aestivum L) were grown in the winters and mungbean (Vigna radiata) and maize in the summers. Immediately after grain harvest, above-ground residues of all crops were either completely removed (−residue), or spread across the plots and incorporated by chisel plough by disc harrow and rotavator (+residue). Fertlizer N rates were nil or 120 kg ha⁻¹ for wheat and nil or 160 kg ha⁻¹ for maize. Our results indicated that post-harvest incorporation of crop residues significantly (p < 0.05) increased the grain and stover yields of maize during both 2000 and 2001. On average, grain yield was increased by 23.7% and stover yield by 26.7% due to residue incorporation. Residue retention also enhanced N uptake by 28.3% in grain and 45.1% in stover of maize. The soil N fertility was improved by 29.2% due to residue retention. The maize grain and stover yields also responded significantly to the previous legume (chickpea) compared with the previous cereal (wheat) treatment. The legume treatment boosted grain yield of maize by 112% and stover yield by 133% with 64.4% increase in soil N fertility. Similarly, fertilizer N applied to previous wheat showed considerable carry over effect on grain (8.9%) and stover (40.7%) yields of the following maize. Application of fertilizer N to current maize substantially increased grain yield of maize by 110%, stover yield by 167% and soil N fertility by 9.8% over the nil N fertilizer treatment. We concluded from these experiments that returning of crop residues, application of fertilizer N and involvement of legumes in crop rotation greatly improves the N economy of the cropping systems and enhances crop productivity through additional N and other benefits in low N soils. The farmers who traditionally remove residues for fodder and fuel will require demonstration of the relative benefits of residues return to soil for sustainable crop productivity.     

不同水分条件下化肥对玉米产量的贡献

以16年长期定位试验为平台,研究了8种施肥制度与4种降雨年景条件下肥料的增产、稳产性能及其对产量的贡献。结果表明:施肥与水分条件对玉米产量均有显著影响,平水年份玉米产量最高,肥料增产效果也达到最佳,其次为丰水年,旱、涝年份最低;N、P和K配施玉米产量最高,无N肥处理作物产量偏低,但在旱、涝条件下P、K肥有利于提高玉米的抗逆性;对玉米产量贡献NPK,单施K肥其在平、丰水年对产量贡献率为负值,说明这一地区K尚未成为玉米生产中的限制因子,其只有与N肥配施才可发挥增产作用。综上,合理的养分配施可以提高肥料对玉米产量的贡献,促进肥料交互作用对产量的提升,同时,适宜的水分条件可使肥料增产作用更好发挥。     

不同肥力农田玉米产量构成差异及施肥弥补土壤肥力的可能性

【目的】农田基础土壤肥力和肥料的投入共同决定着农田的养分供应以及影响作物的生长与产量。明确不同肥力土壤和低肥力农田增施氮肥对玉米生长及产量形成的影响差异,是科学评价土壤培肥和施肥的基础。【方法】本研究设置两个玉米田间试验,试验一选取三块具有基础肥力和产量差异的农田,按土壤肥力由高到低依次命名为农田A、 B和C,采用完全统一施肥管理; 试验二在土壤肥力水平最低的农田C上设置了常规施氮量N 210 kg/hm2,以及在此基础上拔节期增施N 40和80 kg/hm2共3个处理。测定了各农田土壤基础性质,以及0—20 cm土层硝态氮含量,调查了不同生育期玉米的干物质和叶面积,产量和产量构成。【结果】不同肥力水平农田中土壤的潜在矿化氮量与产量的相关性最好。不同肥力水平农田的土壤硝态氮含量没有显著性差异; 低肥力农田增施氮肥处理在拔节期施肥后土壤中的硝态氮含量要大幅度高于常规施肥处理,在抽雄期该差异达到最大值,然后逐步降低。不同肥力水平农田的玉米产量、 每公顷穗数、 穗粒数、 千粒重均随土壤肥力升高而显著增加,其中肥力最高的农田A的玉米产量、 每公顷穗数、 穗粒数和千粒重较肥力最低的农田C分别高20.3%、 5.7%、 5.2%和7.8%。低肥力农田C在拔节期增施氮肥显著提高了产量、 每公顷穗数和穗粒数,对千粒重影响很小,同时降低了收获指数。其中增施氮肥80 kg/hm2处理较常规施氮处理的产量、 公顷穗数和穗粒数显著分别增加了17.1%、 9.2%和4.6%,收获指数降低了8.2%。【结论】高肥力土壤能够持续矿化出更多的无机氮供玉米利用,通过全面提升玉米每公顷穗数、 穗粒数和千粒重来提升产量。低产田在拔节期增施氮肥能够大幅度提高拔节期至抽雄期土壤的硝态氮含量,提高每公顷穗数和穗粒数,进而增加作物产量,但通过增施肥料得到的产量依然达不到高肥力农田的产量水平,而且降低了收获指数。因此,培肥土壤是实现玉米高产高效的基础。     

玉米秸秆还田时间和还田方式对土壤肥力和作物产量的影响

采用微区和田间两种长期定位试验(12年),探讨了玉米秸秆不同还田时间和还田方式对土壤的培肥作用和对作物产量的影响。研究结果表明,玉米秸秆的还田时间以秋天直接还田并配以适量的微生物快腐剂为好,春天施用腐熟的玉米秸秆不但费工费力,而且对土壤肥力和作物产量没有明显的提高作用;玉米秸秆不同还田方式对土壤肥力和作物产量的影响程度不明显,因此生产上应根据因地制宜的原则,确定适合的还田方式。     

Tillage methods and soil and water conservation in Australia

Tillage in Australia has evolved from ‘imported’ European practices to tillage systems more in tune with ‘older’ fragile soils and more severe climatic conditions. Cereal yields are commonly limited by water supply and the native fertility of many soils is poor. Crop/pasture rotations involving pasture legumes have been the mainstay of cereal production in the winter rainfall areas while production in much of the summer rainfall area has relied more on exploiting native fertility. Soil erosion and structural decline are still considered major issues facing long-term production. The general trend in tillage methods is for less tillage and greater retention of crop residues for soil and water conservation.

Tillage experiments have shown that management strategies involving retention of crop residues (stubble), reduced tillage and crop rotation can reduce erosion and improve yield. Results from experimentation are highly variable, both in magnitude and direction of responses to tillage treatments. Much of this variation is due to variation in seasonal conditions. Simulation models are being used to examine management options and to design experiments based on a knowledge of climate variability and physical and biological processes.     

西南紫色土不同施肥措施下土壤综合肥力评价与比较

【目的】 为探求长期不同施肥处理对作物产量的影响和土壤综合肥力的演变，寻求合理评价西南紫色土区域土壤综合肥力的方法。 【方法】 本研究以7年的定位试验的数据为基础，运用内梅罗指数法、相关系数法和因子分析法对不施肥对照 (CK)、化肥优化施用 (OP)、在化肥优化基础上有机肥氮替代50%化肥氮 (MF)、在化肥优化基础上有机肥氮替代100%化肥氮 (OM) 4个处理的土壤肥力进行综合评价。 【结果】 不同施肥处理下蔬菜和玉米的平均产量均表现为MF处理最大。在蔬菜季，MF处理显著提高了产量，相比OP和OM处理，榨菜分别增产27.8%和16.0%，大白菜分别增产28.6%和8.7%；在玉米季，MF处理的产量最大，为9907 kg/hm2，显著高于OP和OM处理，分别增产1199 kg/hm2和1273 kg/hm2。通过分析土壤单项肥力指标与作物产量的相关关系表明，土壤有机质、全氮和有效磷与作物产量均存在显著或极显著正相关关系，表明土壤有机质、全氮和有效磷对紫色土土壤肥力贡献大，是表征紫色土土壤肥力的重要指标。用3种评价方法计算的不同施肥处理的土壤综合肥力指数值 (IFI) 均表现为OM > MF > OP > CK，施用有机肥处理 (MF和OM) 处理IFI值要显著高于优化施肥处理。3种评价方法的IFI值与作物产量均呈显著或极显著关系，但3种评价方法的相关系数平均值从大到小表现为相关系数法 (0.5292) > 内梅罗指数法 (0.5252) > 因子分析法 (0.5130)，表明相关系数法比内梅罗指数法和因子分析法更可靠。 【结论】 在蔬菜?玉米轮作体系下，有机肥氮替代部分化肥氮能增加作物产量，提高土壤综合肥力水平。从3种评价方法的精确性来看，相关系数法比内梅罗指数法和因子分析法更可靠，在实践中优先使用。      

黄潮土养分供应特征及演变规律

１５年定位监测结果表明：不同施肥结构对小麦、玉米产量有明显影响，各处理单产依次为：ＭＮＰＫ〉ＭＮＰ〉ＭＮ〉ＮＰＫ〉ＮＰ〉Ｎ〉Ｍ＾１）〉ＣＫ。长期不施肥区，土壤养分供应不足，产量逐年下降。基础地力贡献率平均产３７．２％，肥料的增产贡献率为６２．８％。在肥料中有机肥占２５．２％，化肥占７４．８％。在化肥中氮占６４．６％，磷占２７．２％，钾占８．２％。有机肥有明显改土培肥作用，有利土壤物理性改善，增强作     

红壤性水稻土施肥的产量效应及与气候、地力的关系

以23a红壤性水稻土化肥定位试验为对象，探讨了不同施肥措施下水稻产量变化及其与气候、地力的关系。结果表明：不同施肥措施的产量效应均显著受气候的年成变化及其交互作用的影响，气候的季相变化因不同施肥措施而异，对CK、NK、NPKM处理影响不大，而对N、NP、NPK处理有强烈的影响；红壤性水稻土基础地力贡献率较稳定，为46．3％，72．0％。随着施肥结构完善，对地力贡献的依赖性表现出NPKM〈NPK〈NK、NP〈N的趋势；各施肥管理水稻平均增产效果表现为NPKM〉NPK〉NK〉NP〉N。连续施用氮（N）肥，增产效果达持续显著水平的年限为17a，钾（K）肥的为98，而磷（P）肥不明显。N肥单施或与P肥、K肥配施，生产稳定性显著下降，且随时间的延长，增产效率均呈线性下降，其下降速率表现出NP〉N〉NK的趋势，至18～218后，产量水平相当或者低于无肥区（CK）。N肥与PK肥配施，可显著提高水稻生产的稳定性和产量，再配施有机肥，水稻增产效果更为明显。