日光温室长期施肥条件下耕层土壤计量化学变化特征

【目的】施肥是保持设施蔬菜地土地生产力的重要措施,但长期高量水肥条件下土壤中碳、氮和磷的化学计量特征并不清楚。【方法】本试验采用室外调查采样结合化验分析的方法,研究褐土区蔬菜保护地不同年限（5、15、20、30a）和大田土壤主要养分碳、氮和磷的化学计量特征。【结果】(1)不同种植年限随着年限增加土壤表层有机质量先增加后降低并趋于稳定,15 a时有机质量达到最大值,比大田增加99.4%;土壤全氮量和全磷量随年限增加整体变化趋势类似有机质量,各年限土壤全氮量和全磷量分别是大田的1.4～2.6倍和1.7～4.5倍,全氮量15 a达最高,而20 a种植年限的全磷量最高。(2)与大田相比,不同种植年限土壤C∶N、N∶P和C∶P化学计量比均随年限增加而递减并趋于稳定,变化分别在8.7～10.3、1.2～1.6和7.7～15.6范围内。土壤表层C、N、P量的增加速度排序为P>N>C,表现为化学计量比C∶P变异最大,N∶P次之,C∶N变异较小。【结论】尽管大棚内肥料投入较高,但目前该褐土区域土壤C∶N、C∶P和N∶P化学计量比在一定范围内维持相对稳定。从长远来看,针对本研究设施蔬菜地磷的持...     

加气条件下土壤N2O排放对硝化/反硝化细菌数量的响应

为揭示加气灌溉及不同灌水量处理设施番茄地土壤N2O排放对土壤微生物的响应,于2016年8—12月在日光温室内进行试验,以充分供水的灌水量(W)为基准,设置0.6W、0.8W和1.0W 3个灌水定额,每个灌水定额又设置加气和不加气处理,共计6个处理:0.6W加气(AI0.6)、0.6W不加气(CK0.6)、0.8W加气(AI0.8)、0.8W不加气(CK0.8)、1.0W加气(AI1.0)和1.0W不加气(CK1.0)。结果表明,番茄生育前期,不同灌溉处理的土壤N2O排放通量呈下降的趋势;移植25 d后,N2O气体维持在较低且稳定的排放水平。与不加气处理相比,不同灌水定额的加气处理增加了土壤N2O排放,平均增加了4.7%;且随着灌水量的增加,土壤N2O排放也在增加,平均增加了1.9%,但处理间差异性均不显著(P0.05)。就番茄全生育期微生物数量均值而言,加气较不加气处理增加了土壤硝化细菌数量,平均增加了2.1%;但加气减小了土壤反硝化细菌数量,平均降低了9.7%(P0.05)。而随着灌水量的增加,土壤硝化细菌和反硝化细菌数量均逐渐增加(P0.05)。相关分析表明,土壤N2O排放与土壤水分和土壤温度呈极显著正相关关系(P0.01),与土壤反硝化细菌数量呈极显著负相关关系(P0.01)。试验结果为研究设施菜地土壤硝化和反硝化反应过程及氮循环奠定了理论基础。     

马铃薯连作土壤微生物特性与土传病原菌的相互关系

为了揭示连作马铃薯土壤微生物群体与土传病原菌的相互关系,采用盆栽试验,以裸地(CK)和轮作(R)为对照,研究了不同马铃薯连作年限条件下(马铃薯连作1 a(T1)、3 a(T3)和5 a(T5))土壤微生物种群结构、酶活性、微生物量碳氮和土传病原菌的变化。结果表明,与R处理相比,T1、T3、T5处理土壤细菌/微生物的比例逐渐下降,土壤真菌/微生物和放线菌/微生物的比例逐渐增加。与CK和R处理相比,随连作年限的增加细菌/真菌显著下降。马铃薯连作后镰刀菌数量呈上升趋势,T3和T5处理茄病镰刀菌和尖胞镰刀菌数量显著高于硫色镰刀菌。连作后土壤蔗糖酶和脲酶活性呈降低趋势,R处理与T5处理差异显著,土壤过氧化氢酶呈先下降后上升的趋势,土壤多酚氧化酶活性呈动态上升趋势。连作马铃薯微生物量C、N量比轮作显著降低,T1、T3和T5处理土壤微生物量碳/氮比显著高于R处理。土壤细菌、微生物量碳氮显著促进土壤蔗糖酶和脲酶活性,土壤真菌抑制微生物量氮、蔗糖酶和脲酶活性,显著促进镰刀菌,而镰刀菌抑制细菌、微生物量碳氮、蔗糖酶和脲酶活性,从而导致了病原菌数量增多,土壤微生物的生存环境恶化。     

无压地下灌溉条件下土壤水分入渗特性研究

通过室内土箱试验,研究了不同供水压力(-3、0、3cm)和灌水器孔径(4、6、8mm)对无压灌溉下累积入渗量、湿润峰动态变化以及土壤含水率分布的影响。结果表明,不同供水压力和灌水器孔径下累积入渗量、土壤湿润体水平向和垂直向最大湿润距离均随入渗时间的增加以幂函数形式增大,湿润体内土壤含水率沿湿润球体半径方向以二次抛物线形式逐渐减小。随着供水压力的增大,相同时段内的土壤入渗量增大,湿润锋的迁移速度也随之变快;在供水压力相同的条件下,大孔径灌水器在相同时段内的土壤入渗量、水平向和垂直向最大湿润距离均比小孔径灌水器情况下的数值要大。在中大灌水器孔径条件下,土壤含水率随供水压力增大而增大,而小孔径情况下差异显著。     

水氮耦合对黑土稻田土壤呼吸与碳平衡的影响

为探明不同水氮耦合方式对东北黑土区稻田碳循环的影响,以黑龙江省黑土稻田为研究对象,于2018年进行大田试验,试验设置常规灌溉(F)与控制灌溉(C)两种灌水方式,全生育期施氮量设置0、85、110、135 kg/hm~24个水平(N0、N1、N2、N3),测定了8种不同水氮耦合方式下水稻不同生育期平均土壤呼吸速率、微生物呼吸速率和根呼吸速率的变化以及水稻收获后各器官的固碳量。结果表明,水稻植株总固碳量为446. 49～716. 92 g/m~2,各处理水稻收获后各器官固碳量从大到小依次为穗、茎、叶、根,分别占植株总固碳量的53. 69%～59. 44%、27. 42%～30. 12%、7. 24%～8. 96%、4. 71%～8. 35%。控制灌溉模式能提高水稻植株固碳量,其中CN2处理的总固碳量最大。相同施氮量、控制灌溉模式下,茎、叶、根固碳量均大于常规灌溉模式,除CN0处理穗固碳量低于FN0处理外,其余相同施氮量、控制灌溉模式下的穗固碳量均大于常规灌溉模式。不同水氮耦合方式下,水稻从返青期至乳熟期各生育期平均土壤呼吸速率、微生物呼吸速率、根呼吸速率均呈先升高、后降低的趋势,且均在分蘖期达到峰值。除返青期外,与不施肥处理相比,施肥后各生育期平均土壤呼吸速率、微生物呼吸速率和根呼吸速率均增大,且随着施氮量的增加而增大。控制灌溉模式下各施氮量处理水稻各生育期(除返青期外)平均土壤呼吸速率、微生物呼吸速率和根呼吸速率均高于常规灌溉模式下相同施氮量处理。8种不同水氮耦合方式下黑土稻田均表现为较强的碳"汇",控制灌溉模式能够增加碳"汇"强度,其中CN2处理碳"汇"强度最大。本研究结果可为提高黑土稻田固碳减排潜力提供理论基础,为估算区域乃至全球碳平衡提供数据支撑。     

远程智能控制滴灌土壤入渗多参数节水效果试验研究

基于使用远程智能控制系统,研究扬黄灌区土壤水分入渗试验,分析讨论了2种类型土壤,基于不同压力、埋深程度研究土壤水分入渗速度、湿润锋、时间等,并初步总结出不同外界条件下土壤入渗的变化规律,为保持水土、提高土壤水分生产力提供重要的科学依据。研究表明:压力、贴片式滴灌带的埋深程度对土壤累计入渗量和入渗速度的影响都比较明显。土壤累积入渗量随着压力水头的增加而增大,湿润运移距离位移不单单和环境有关系,压力对其的影响也很大。在越强的压力作用下,水的运送速度越快,这样土壤的入渗速度就越快。速度的增大也加快了各个方向的运移速率,从而达到在短时间内入渗大面积的土壤,增大了运移距离。实验结果显示,湿润锋能够在压力为0.2 MPa的情况下达到最大运移距离;埋深程度也同样影响着土壤累积入渗量和土壤的累计入渗速度,经试验测量埋深10 cm土壤入渗量最大,且地表不宜蒸发到。     

宁夏葡萄园土壤微生物量及土壤酶活性动态变化

【目的】探讨宁夏长期种植葡萄后土壤微生物量及土壤酶活性的时间、空间变化规律。【方法】本试验以宁夏种植20 a的葡萄园为研究对象,分别在不同物候期(萌芽展叶期、开花坐果期、果实成熟期及落叶期)和不同土层深度(0～20、20～40 cm和40～60 cm)采集葡萄的根际土壤和非根际土壤,测试土壤的微生物生物量碳、氮、磷和土壤脲酶、过氧化氢酶、磷酸酶和蔗糖酶的活性。【结果】根际土壤微生物量碳、氮量随着土层的加深逐渐降低,非根际土壤微生物量碳、氮量随着土层的加深逐渐升高。土壤微生物量磷在根际土壤中随土层加深其质量浓度逐渐升高,非根际土壤中微生物量磷随着土层加深其质量浓度降低。根际在0～20 cm对土壤微生物量碳、氮的富集率最高,分别为30.50%和45.26%;而土壤微生物量磷在40～60 cm土层达到最高,富集率为59.29%。根际土壤的脲酶、过氧化氢酶、磷酸酶和蔗糖酶活性随着土层的加深其活性逐渐降低;而非根际土壤的脲酶、过氧化氢酶和磷酸酶活性随着土层的加深其活性逐渐升高。根际土壤和非根际土壤中脲酶、蔗糖酶和过氧化氢酶的活性随着物候期表现出先降低后升高的变化趋势,而土壤磷酸酶的活性出现先升高后降低的变化趋势。通过Pearson相关系数对土壤的酶活性和土壤微生物生物量进行相关分析可知,土壤磷酸酶活性和蔗糖酶活性与微生物生物量碳呈显著正相关,与微生物生物量氮呈极显著正相关,土壤脲酶活性与微生物量磷呈显著负相关。【结论】长期种植葡萄后,根际土壤微生物碳和氮有明显的富集效应。根际土壤与非根际土壤的四种土壤酶活性变化规律不一致,可能与葡萄根际分泌物及土壤微生物多样性有关,需进一步研究。     

渗灌用黏土基微孔陶瓷灌水器入渗性能研究

针对3种孔径相同开口孔隙率和渗流面积不同的黏土基微孔陶瓷灌水器,进行了水力性能和土壤入渗试验研究。结果表明,相同条件下微孔陶瓷开口孔隙率和渗流面积越大,灌水器渗流量越大;灌水器入渗性能受灌水时间、土壤类型和进口压力的影响。随着灌水时间延长土壤含水率增加,入渗速率减小;在无压条件下,黄绵土入渗速率较砂土大,随着进口压力增大,砂土入渗速率大于黄绵土入渗速率;同时随着进口压力增大灌水器入渗速率增大且稳定时间缩短。     

秸秆还田配施氮肥对土壤碳氮含量与玉米生长的影响

为明确宁夏扬黄灌区秸秆还田条件下的适宜施氮量,在玉米秸秆全量还田条件下,设4种纯氮施用水平(0 kg/hm~2(N0)、150 kg/hm~2(N1)、300 kg/hm~2(N2)、450 kg/hm~2(N3)),以秸秆还田不施氮肥(N0)为对照,研究了秸秆还田配施不同纯氮水平对土壤有机碳氮含量、微生物量碳氮含量和酶活性及其对玉米生长的影响。结果表明,秸秆还田配施氮肥有利于耕层土壤有机碳和全氮含量的提高,随施氮量的增加,土壤碳氮比降低,其中以N2和N3处理对提高耕层有机碳氮含量效果最佳。秸秆还田条件下土壤微生物量碳氮比随施氮量的增加而降低,N2处理对微生物量碳含量、N3处理对微生物量氮含量的提高作用最为显著。秸秆还田配施氮肥能显著提高土壤脲酶、过氧化氧酶、碱性磷酸酶和蔗糖酶活性,以N2和N3处理的改善效果较优。秸秆还田配施氮肥对玉米前期生长影响不显著,而N2处理对中后期玉米生长具有显著促进作用。2年玉米籽粒产量以N2处理增产效果最佳,平均较N0处理提高22.0%。通过2年研究结果表明,在宁夏扬黄灌区实施秸秆还田配施氮肥措施可增加土壤有机碳氮含量,调节土壤碳氮比,促进玉米生长,进而提高玉米产量,以秸秆还田配施纯氮300 kg/hm~2效果最佳。     

微生物及C∕N比对果桑枝条堆肥腐熟的影响

以较大质量堆体（500 kg）为对象，探讨微生物及C/N比对果桑枝条堆肥腐熟效果的影响。以桑枝条和鸡粪为原料，调整堆体的C/N比为20∶1、25∶1和30∶1，分别搅拌4%、4%和6%的微生物，研究微生物及C/N比对桑枝条堆肥腐熟效率及肥力的影响。结果显示，微生物接种量为6%，C/N比为30∶1的1号堆腐熟效率最高、效果最好。在堆肥过程中，保持45℃以上的时间15d，可有效降解难降解的有机物。堆肥结束后，C/N比降至11.73∶1，可溶性腐殖质和总养分的增幅及其含量的积累均最高，发芽指数达到133.91%，T值为0.39。通过分析可知，C/N比是影响桑枝条堆肥腐熟效率的重要因素，适宜的C/N比有利于微生物的分解活动和肥力的增加；增加微生物接种量，能够提高其腐熟效率。      

Soil microbial response, water and nitrogen use by tomato under different irrigation regimes

The objectives of this study were to investigate the effects of full irrigation (FI), deficit irrigation (DI) and partial root-zone drying (PRD) on plant biomass, irrigation water productivity (IWP), nitrogen use efficiency (NUE) of tomato, and soil microbial C/N ratio. The plants were grown in pots with roots split equally between two soil compartments in a climate-controlled glasshouse. During early fruiting stage, plants were exposed to FI, DI, and PRD treatments. In FI, both soil compartments were irrigated daily to a volumetric soil water content of 18%; in PRD, only one soil compartment was irrigated to 18% while the other was allowed to dry to ca. 7-8%, then the irrigation was shifted; in DI, the same amount of water used for the PRD plants was equally split to the two soil compartments. The results showed that, the FI treatment produced significantly higher dry biomasses of leaves, stems, and fresh weight of fruit and water productivity of aboveground dry biomass production than either DI or PRD, however, fruit IWP in DI was 25% higher than that of FI, and harvest index in DI and PRD were 50% and 22% higher than FI, respectively, for the 26% and 23% less water used in the DI and PRD, respectively, than the FI treatment. The DI treatment caused the smallest losses of N and highest N use efficiency by fruit. Both DI and PRD caused a significant increase in the soil microbial C/N ratio, meaning ratio of fungal biomass was high at low soil water contents. The result indicates that more work is needed to link the aboveground N uptake and the underground microbially mediated N transformation under different water-saving irrigation regimes.     

A simulation-based analysis of productivity and soil carbon in response to time-controlled rotational grazing in the West African Sahel region

In the Sahel region of West Africa, the traditional organization of the population and the grazing land avoided overexploitation of pastures. Since independence in the 1960s, grazing lands have been opened to all without specific guidance, and the vulnerability of the pastures to degradation has increased. Rotational grazing is postulated as a possible solution to provide higher pasture productivity, higher animal loads per unit land, and perhaps improved soil carbon storage. The objective of this study was to conduct a simulation-based assessment of the impact of rotational grazing management on pasture biomass production, grazing efficiency, animal grazing requirement satisfaction, and soil carbon storage in the Madiama Commune, Mali. The results showed that grazing intensity is the primary factor influencing the productivity of annual pastures and their capacity to provide for animal grazing requirements. Rotating the animals in paddocks is a positive practice for pasture protection that showed advantage as the grazing pressure increased. Increasing the size of the reserve biomass not available for grazing, which triggers the decision of taking the animals off the field, provided better pasture protection but reduced animal grazing requirements satisfaction. In terms of soil carbon storage, all management scenarios led to reduction of soil carbon at the end of the 50-year simulation periods, ranging between 4% and 5% of the initial storage. The differences in reduction as a function of grazing intensity were of no practical significance in these soils with very low organic matter content, mostly resistant to decomposition.     

Carbon retention in the soil-plant system under different irrigation regimes

Carbon (C) sequestration through irrigation management is a potential strategy to reduce C emissions from agriculture. Two experiments (Exps. I and II) were conducted to investigate the effects of different irrigation strategies on C retention in the soil-plant system in order to evaluate their environmental impacts. Tomato plants (Lycopersicon esculentum L., var. Cedrico) were grown in split-root pots in a climate-controlled glasshouse and were subjected to full irrigation (FI), deficit irrigation (DI) and alternate partial root-zone irrigation (PRI) at early fruiting stage. In Exp. I, each plant received 2.0 g chemical nitrogen (N), while in Exp. II, 1.6 g chemical N and maize residue containing 0.4 g organic N were applied into the pot. The results showed that, in both experiments, the concentration and the amount of total C in the soil were lower in FI and PRI as compared to DI, presumably due to a greater microbial activity in the two treatments; particularly the PRI induced drying and wetting cycles of the soils may cause an increase of microbial activities and respiration rate, which could lead to more C losses from the soil. However, in both experiments the total C concentration in the PRI plants was the highest as compared with the FI and DI plants, and this was seemingly due to improved plant N nutrition under the PRI treatment. Consequently, the total amount of C retained in the soil-plant system was highest in the FI and was similar, but lower, for the PRI and DI. The different N input in the two experiments might have affected the C retention in the soil and in the plant biomass. Nevertheless, with a same degree of water saving, PRI was superior to DI in terms of enhancing C concentration in the plant biomass, which might have contributed to a better fruit quality in tomatoes as reported by [Zegbe et al., 2004] and [Zegbe et al., 2006].     

Mechanism of improved phosphate uptake efficiency in banana seedlings on acidic soils using fertigation

Fertigation improves nutrient uptake efficiency greatly, while the mechanism of increased nutrient uptake efficiency remains unclear. In this study, the effects of conventional phosphate (P) fertilization (by mixing fertilizer with soils) and fertigation (by dissolving fertilizer in water) on P uptake were compared in banana (Musa sapientum) seedlings. Results indicated that, compared with conventional fertilization, fertigation increased the concentration of available P by 108% and decreased the P sorption index by 31% in the 0-8 cm surface soil of banana roots. Fertigation enhanced the transformation of different P fractions, increased the concentrations of aluminum-bound P (Al-P), iron-bound P (Fe-P) and occluded-P (O-P), and decreased the pH value by 0.3 units. However fertigation did not influence the activity of acid phosphatase, but increased microbial biomass and root activity by 25.5-67.8%. Furthermore, fertigation increased the root distribution in the 0-8 cm soil layer by 7.8-9.4% compared with conventional fertilization. These results suggest that fertigation increases P uptake efficiency as the result of increased root activity, root distribution, microbial biomass and reduced P sorption index in the surface soil of banana seedlings.     

Hydro-physical responses of gypseous and non-gypseous soils to livestock grazing in a semi-arid region of NE Spain

Pasture productivity depends on soil hydro-physical properties, which in turn are deeply affected by livestock grazing. However, the comparative response of different soil types, and particularly gypseous soil types, to grazing has hardly been studied before. This paper compares the effect of grazing on the soil hydro-physical properties of silty gypseous (Gy) and non-gypseous (NGy) soils located in a semi-arid region (Middle Ebro Valley, NE, Spain). Two different soil managements were selected: ungrazed natural shrubland (N) and grazed shrubland (GR) soils. The gypsum, CaCO₃ and organic matter content (OM), soil texture, soil bulk density (ρ_b), penetration resistance (PR), saturated sorptivity (S), hydraulic conductivity (K), and the water retention curve (WRC) for undisturbed soil samples from 1 to 10 cm depth soil layer were measured. The ρ_b and PR in NGy soils were significantly higher than those observed in the Gy ones. Soil compaction due to grazing treatment tended to increase ρ_b and decrease the K and S values. While no differences in PR were observed in the Gy soils between grazing treatments, the PR measured in the NGy soils under GR was significantly higher than the corresponding values observed under N. Differences in K and S between GR and N treatments were only significant (p < 0.05) in NGy soils, where K and S values under the N treatment were almost four times greater than the corresponding values measured under GR. Overall, no differences in the WRCs were observed between soil types and grazing treatments. While the WRCs of NGy soils were not significantly affected by the grazing treatment, Gy soils under N treatment present a significantly higher level of soil macropores than under GR treatment. The hydro-physical features of Gy soils tended to be less affected by grazing than those of the NGy soils. These results suggest that livestock grazing, in both Gy and NGy soils, has a negative effect on the physical soil properties, which should be taken into account by land managers of these semi-arid regions where silty gypseous and non-gypseous areas coexist.     

Sustainable agriculture: A case study of a small Lopez Island farm

Overreliance on fossil fuel based inputs, and transport of inputs and products is seen by many as a threat to long-term agricultural and food system sustainability. Many organic, biodynamic, and low-input farmers limit off-farm inputs, attempting instead to farm within the carrying capacity of their land or local environment. These farmers often accept lower farm productivity because they see reduced reliance on non-renewable inputs as more sustainable. Documentation of low-input agricultural systems through both replicated research trials and case studies is needed in order to better understand perceived and real advantages and tradeoffs. The goal of our study was twofold: (1) to compare liming and biodynamic (BD) preparations in improving pasture on a moderately acidic pasture soil through stimulation of soil microbial activity; (2) to place these findings within the context of a whole farm analysis of economic, plant, and animal health. Treatments included lime, the Pfeiffer Field Spray plus BD compost preparations, and untreated controls. Soil pH, total C and N, microbial activity, forage biomass, and forage quality were evaluated over two growing seasons. Both lime and the Pfeiffer Field Spray and BD preparations were only moderately effective in raising soil pH, with no effect on soil microbial activity or forage yield. Lime significantly reduced forage crude protein but the practical implications of this are questionable given the overall low quality of the forage. While the farm is profitable and economically stable and the animals healthy, the need for future targeted nutrient inputs cannot be ruled out for sustainable long-term production.     

生物炭对砂壤土节水保肥及番茄产量的影响研究

采用室内盆栽试验定量分析方法,研究了砂壤土中施加不同含量生物炭对土壤节水保肥及提高番茄产量的影响。试验共设5个处理:不添加生物炭(CK),每1 kg干土加生物炭10 g(C10)、20 g(C20)、40 g(C40)和60 g(C60)。结果表明:施加生物炭处理有利于提高土壤肥力,其中较高施用量的处理增幅明显。与CK相比,C60处理的有机质含量增加560%;C60和C40的碱解氮含量分别增加110%和130%,速效磷含量增加410%和290%,速效钾含量增加290%和150%。随着生物炭施用量的增大土壤含水率呈现递增趋势,其中C60较CK提高170%。较高生物炭施用量可以有效增加番茄产量,C60和C40处理分别比CK提高98%和170%,其中C40处理的产量增幅最大。相关分析可知,水、肥因素对番茄产量影响显著,相关性超过80%,通过在砂壤土中施加生物炭可有效提高肥水利用效率,提高番茄产量。     

Interrelationships between net primary production,ground-storey condition and grazing capacity of the Acacia aneura rangelands of semi-arid Australia

A simulation model which estimates the net primary production of the ground-storey component of the extensively grazed Acacia aneaura rangelands of semi-arid Queensland, Australia, was applied to the assessment of grazing capacity. The method described represents an alternative approach to the traditional method used by land administrators. Historic climatic records for a continuous period of 25 years were analyzed for one centre. Annual live herbage biomass production fluctuated widely in relation to both climate and grund-storey condition class. Herbage biomass carryover from year to year decreased significantly as the level of herbage utilization through animal consumption increased. At a conservative level of use, herbage biomass carryover provided an important reserve to supplement the smaller amount of live biomass produced in low rainfall years. Consequently, grazing capacity was related to the total herbage biomass available to the grazing animal at the end of each summer growing period. There were only small changes in the mean value of end-of-summer peak herbage biomass crop and sheep carrying capacity over the excellent to good ground-storey condition classes. However, there was a pronounced decline in these values as condition class decreased from moderate to poor.The implications of this method assessing grazing capacity for semi-arid rangeland management and administration are discussed.     

Performance of CERES-Rice and CERES-Wheat models in rice–wheat systems: A review

Rice–wheat (RW) systems are critical to food security and livelihoods of rural and urban poor in south Asia and China, and to regional economies in southeast Australia. The sustainability of RW systems in south Asia is, however, threatened by yield stagnation or decline, and declining partial factor productivity, soil organic C and water availability. Crop models potentially offer a means to readily explore management options to increase yield, and to determine trade-off between yield, resource-use efficiency and environmental outcomes. This paper reviews the performance of CERES-Rice and CERES-Wheat in Asia and Australia in relation to their potential application towards increasing resource use efficiency and yield of RW systems.

The performance of the models was evaluated using simulated and observed data on anthesis and maturity dates, in-season LAI and growth, final grain yield and its components, and soil water and N balances from published studies across Asia and Australia, and then by computing the statistical parameters for the major characters. Over the four data sets examined for anthesis and six for maturity dates, CERES-Rice predicted those dates fairly well (normalised RMSE = 4–5%; D-index = 0.94–0.95), but over the 11 sets for grain and 4 for biomass yield, the predictions were more variable (normalised RMSE = 23% for both; D-index 0.90 and 0.76, for grain and biomass, respectively). Model performance was poorer under conditions of low N, water deficit, and low temperatures during the reproductive stages. Over the three data sets examined, CERES-Wheat predicted the anthesis and maturity dates quite well (normalised RMSE = 4–5%; D-index = 0.94–0.99), and over eight sets for grain and two sets for biomass yield the model predicted them also reasonably well (RMSE = 13–16%; D-index = 0.86–0.97). Only one study evaluated the DSSAT RW sequence model with fairly satisfactory predictions of rice and wheat yields over 20 years with adequate N, but not the long-term change in soil organic C and N. Predictions of in-season LAI and crop growth, and soil and water processes were quite limited to investigate the robustness of model processes.

Application of models to evaluate options to increase water and N use efficiency requires the ability to perform well at the margin where deficit stress begins. While both models generally perform satisfactorily under water and N non-limiting conditions, the little evidence available suggests that they do not perform well under resource-limiting situations. We recommend that the models’ key processes under the water and N limiting conditions be further evaluated urgently. The DSSAT sequence model also needs to be further evaluated against observations for a range of locations and management using data from long-term experiments in RW systems.