Yield performance and optimal nitrogen and phosphorus application rates in wheat and faba bean intercropping

Yield performance in cereal and legume intercropping is related to nutrient management, however, the yield response of companion crops to nitrogen (N) input is inconclusive and only limited efforts have focused on rationed phosphorous (P) fertilization. In this study, two multi-year field experiments were implemented from 2014–2019 under identical conditions. Two factors in a randomized complete block design were adopted in both experiments. In field experiment 1, the two factors included three planting patterns (mono-cropped wheat (MW), mono-cropped faba bean (MF), and wheat and faba bean intercropping (W//F)) and four N application rates (N0, 0 kg N ha^–1; N1, 90 and 45 kg N ha^–1 for wheat and faba beans, respectively; N2, 180 and 90 kg N ha^–1 for wheat and faba beans, respectively; and N3, 270 and 135 kg N ha^–1 for wheat and faba beans, respectively). In field experiment 2, the two factors included three P application rates (P0, 0 kg P₂O₅ ha^–1; P1, 45 kg P₂O₅ ha^–1; and P2, 90 kg P₂O₅ ha^–1) and the same three planting patterns (MW, MF, and W//F). The yield performances of inter- and mono-cropped wheat and faba beans under different N and P application rates were analyzed and the optimal N and P rates for intercropped wheat (IW) and MW were estimated. The results revealed that intercropping favored wheat yield and was adverse to faba bean yield. Wheat yield increased by 18–26%, but faba bean yield decreased by 5–21% in W//F compared to MW and MF, respectively. The stimulated IW yield drove the yield advantage in W//F with an average land equivalent ratio (LER) of 1.12. N and P fertilization benefited IW yield, but reduced intercropped faba bean (IF) yield. Nevertheless, the partial LER of wheat (pLER_wheat) decreased with increasing N application rates, and the partial LER of faba bean (pLER_{faba bean}) decreased with increasing P application rates. Thus, LER decreased as N input increased and tended to decline as P rates increased. IW maintained a similar yield as MW, even under reduced 40–50% N fertilizer and 30–40% P fertilizer conditions. The estimated optimum N application rates for IW and MW were 150 and 168 kg ha^–1, respectively, and 63 and 62 kg ha^–1 for P₂O₅, respectively. In conclusion, W//F exhibited yield advantages due to stimulated IW yield, but the intercropping yield benefit decreased as N and P inputs increased. Thus, it was concluded that modulated N and P rates could maximize the economic and ecological functions of intercropping. Based on the results, rates of 150 kg Nha^–1 and 60 kg P₂O₅ ha^–1 are recommended for IW production in southwestern China and places with similar conditions.     

Increased ammonification,nitrogenase, soil respiration and microbial biomass N in the rhizosphere of rice plants inoculated with rhizobacteria

Azospirillum brasilense and Pseudomonas fluorescens are well-known plant growth promoting rhizobacteria. However, the effects of A. brasilense and P. fluorescens on the N cycles in the paddy field and rice plant growth are little known. This study investigated whether and how A. brasilense and P. fluorescens contribute to the N transformations and N supply capacities in the rhizosphere, and clarified the effects of A. brasilense and P. fluorescens on the N application rate in rice cultivation. Inoculations with A. brasilense and P. fluorescens coupled with N application rate trials were conducted in the paddy field in 2016 and 2017. The inoculations of rice seedlings included four treatments: sterile saline solution(M_0), A. brasilense(Mb), P. fluorescens(Mp), and co-inoculation with a mixture of A. brasilense and P. fluorescens(Mbp). The N application rate included four levels: 0 kg N ha~(–1)(N_0), 90 kg N ha~(–1)(N_(90)), 180 kg N ha~(–1)(N_(180)), and 270 kg N ha~(–1)(N_(270)). The results indicated that the Mbp and Mp treatments significantly enhanced the ammonification activities in the rhizosphere compared with the M_0 treatment, especially for higher N applications, while the Mbp and Mb treatments greatly enhanced the nitrogenase activities in the rhizosphere compared with the M_0 treatments, especially for lower N applications. Azospirillum brasilense and P. fluorescens did not participate in the nitrification processes or the denitrification processes in the soil. The soil respiration rate and microbial biomass N were greatly affected by the interactions between the rhizobacteria inoculations and the N fertilizer applications. In the Mbp treatment, N supply capacities and rice grain yields showed no significant differences among the N_(90), N_(180), and N_(270) applications. The N application rate in the study region can be reduced to 90 kg N ha~(–1) for rice seedlings co-inoculated with a mixture of A. brasilense and P. fluorescens.     

Effects of silicon amendment on the occurrence of rice insect pests and diseases in a field test

Rice is one of the most important staple foods for the world population,but it is attacked by a number of destructive pests.While evidence from greenhouse and laboratory tests has shown that silicon(Si)amendment can confer enhanced resistance to pests in rice,few studies have directly demonstrated the Si-mediated protection from pests in a field situation.In this study,field plots with silicon amendments at 0,75,150 and 300 kg SiO_2 ha~(–1) in early-and late-season rice were employed to evaluate the effects of silicon amendment on the occurrence of major insect pests and diseases and rice yield.Compared with the control plots without silicon amendment,plant damage by stem borer and leaf folder and population size of planthopper were significantly lower in three to five of the seven monitoring observations in each season in the plots amended with 300 kg SiO_2 ha~(–1).The disease index of rice blast in the early-season rice was lower in the plots amended with Si at 300 kg SiO_2 ha~(–1) than in the control plots,while Si protection from rice blast in the late-season rice and from rice sheath blight in the early-season rice were not apparent.An insignificant increase of rice yield by 16.4%(604 kg ha~(–1))was observed in the plots amended with 300 kg SiO_2 ha~(–1) over the control plots.Our results indicate that Si amendment at 300kg SiO_(2 )ha~(–1) can provide substantial protection from some of the rice pests under field conditions.These findings support the recommendation of silicon amendment as a key component of integrated management of rice pests.     

Suitability of the DNDC model to simulate yield production and nitrogen uptake for maize and soybean intercropping in the North China Plain

Intercropping is an important agronomic practice. However, assessment of intercropping systems using field experiments is often limited by time and cost. In this study, the suitability of using the DeNitrification DeComposition(DNDC) model to simulate intercropping of maize(Zea mays L.) and soybean(Glycine max L.) and its aftereffect on the succeeding wheat(Triticum aestivum L.) crop was tested in the North China Plain. First, the model was calibrated and corroborated to simulate crop yield and nitrogen(N) uptake based on a field experiment with a typical double cropping system. With a wheat crop in winter, the experiment included five treatments in summer: maize monoculture, soybean monoculture, intercropping of maize and soybean with no N topdressing to maize(N0), intercropping of maize and soybean with 75 kg N ha~(–1) topdressing to maize(N75), and intercropping of maize and soybean with 180 kg N ha~(–1) topdressing to maize(N180). All treatments had 45 kg N ha~(–1) as basal fertilizer. After calibration and corroboration, DNDC was used to simulate long-term(1955 to 2012) treatment effects on yield. Results showed that DNDC could stringently capture the yield and N uptake of the intercropping system under all N management scenarios, though it tended to underestimate wheat yield and N uptake under N0 and N75. Long-term simulation results showed that N75 led to the highest maize and soybean yields per unit planting area among all treatments, increasing maize yield by 59% and soybean yield by 24%, resulting in a land utilization rate 42% higher than monoculture. The results suggest a high potential to promote soybean production by intercropping soybean with maize in the North China Plain, which will help to meet the large national demand for soybean.     

水稻和不同品种苋菜间作对水稻产量、根区速效养分及砷累积的影响

【目的】探究水稻与苋菜间作对水稻产量、根区速效养分及水稻各部位吸收累积As的影响。【方法】通过小区试验研究水稻单作(对照)、水稻与圆叶白苋菜间作、水稻与籽粒苋间作、水稻与红苋菜间作条件下水稻产量、根际土壤速效养分与有机质含量、As累积量的变化。【结果】4个处理水稻收获期地上部、地下部、谷壳和糙米中As含量均表现为:水稻与圆叶白苋菜间作水稻与籽粒苋间作水稻与红苋菜间作水稻单作。与对照相比,水稻与圆叶白苋菜间作显著提高了水稻地上部、地下部、谷壳和糙米As含量,增幅分别为88.50%、65.38%、68.25%和45.45%;对土壤As的提取量为5.44 mg·m~(-2),显著高于对照,为对照的1.67倍;水稻单株生物量显著高于对照、与红苋菜间作和与籽粒苋间作,地上部生物量比对照提高63.79%。与水稻单作相比,间作处理水稻单位面积产量比对照显著下降,间作中单位面积产量最高的为与圆叶白苋菜间作,为对照的59.15%;间作处理水稻根际土壤速效养分、有机质含量均有不同程度的增加。【结论】水稻与苋菜间作,水稻单位面积产量降低,地上部、地下部、谷壳和糙米中As含量以及根区土壤速效养分与有机质含量显著提高。水稻与圆叶白苋菜间作能从As污染土壤中提取最多的As,生产出的苋菜符合国家安全标准,为最优方案。     

Effects of the potassium application rate on lipid synthesis and eating quality of two rice cultivars

Lipid content has an important effect on rice eating quality, but the effects of fertilizer application rate on the lipid synthesis and eating quality of rice are not well understood. Potassium (K) has a strong influence on rice quality and the requirement for K fertilizer in rice is greater than for nitrogen (N) and phosphorus (P) fertilizers. To investigate the effects of K fertilizer on the lipid synthesis and eating quality of rice, we used Nanjing 9108 (NJ9108, japonica) and IR72 (indica) rice as experimental materials and four K levels: K0 (0 kg ha^–1), K1 (90 kg ha^–1), K2 (135 kg ha^–1) and K3 (180 kg ha^–1). The results showed that the lipid content, free fatty acid (FFA) content, unsaturated fatty acid (UFA) content, malonyl-CoA (MCA) content, phosphatidic acid (PA) content, lipid synthesis-related enzyme activities and eating quality first increased and then decreased with increasing K in both cultivars. The maximum values were obtained under K2. However, the saturated fatty acid (SFA) content showed the opposite trend. No significant differences were found in pyruvate (PYR) content among the K treatments. The protein and oxaloacetic acid (OAA) contents and phosphoenolpyruvate carboxylase (PEPCase) activity of NJ9108 first decreased and then increased with increasing K, and the minimum values were obtained under K2; while IR72 showed the opposite trend and the maximum values were obtained under K1. Overall, increasing K optimized the fatty acid components and increased the lipid content and eating quality of rice by enhancing lipid synthesis-related enzyme activities and regulating substrate competition for lipid and protein synthesis. The optimal K application rate for lipid synthesis, eating quality and grain yield was 135 kg ha^–1 for both cultivars.     

Transfer characteristics of nitrogen fixed by leguminous green manure crops when intercropped with maize in northwestern China

To ascertain the possibility of cultivating maize using biological nitrogen fixation (BNF) by leguminous green manure crops in maize/leguminous green manure intercropping systems, BNF and nitrogen (N) transfer were studied in Xining and Wuwei, two typical northwestern Chinese cities. The experimental treatments included monocultured maize, monocultured green manures (hairy vetch and common vetch), and their intercropping systems. The proportions of N derived from the atmosphere (%N_dfa) in intercropping systems were not significantly different from that in monocultured green manure systems at either experimental site, except for that in hairy vetch (HV) in Xining. The amount of N derived from the atmosphere (N_dfa) of common vetch (CV) significantly decreased from 1.16 and 1.10 g/pot in monoculture to 0.77 and 0.55 g/pot when intercropped with maize, in Xining and Wuwei, respectively, and the N_dfa of HV when intercropped significantly decreased from 1.02 to 0.48 g/pot in Xining. In the intercropping systems in Xining and Wuwei, the amounts of N transferred (N_transfer) from CV to maize were 21.54 and 26.81 mg/pot, accounting for 32.9 and 5.9% respectively of the N accumulation in maize, and the values of N_transfer from HV to maize were 39.61 and 46.22 mg/pot, accounting for 37.0 and 23.3%, respectively, of the N accumulation in maize. Path analysis showed that soil nutrient and green manure biomass were mainly related to N_dfa, and that δ¹⁵N had a primary relationship with N_transfer. We found that 5.9–37.0% of N accumulation in maize was transferred from green manures, and that the N transfer ability to maize of HV was higher than that of CV. In conclusion, intercropping with leguminous green manures provided a feasible way for maize to effectively utilize biologically fixed N.     

氮优化措施对间作水稻(黄壳糯、合系41)产量和稻瘟病发生的影响

 以云南糯稻黄壳糯和杂交稻合系41间作为研究对象,通过田间试验,根据叶绿素适时测定结果确定氮肥施用量的方法,研究了氮优化施肥对黄壳糯和合系41间作的产量和稻瘟病发生的影响。结果表明,与传统施氮（180kg N/hm²）相比,优化施氮用量仅为150kg N/hm²,化学氮肥施用量减少了16.7%,无论是单作还是间作,杂交水稻合系41的产量基本保持不变,而黄壳糯产量显著增加。单作条件下两个试验点分别增产380%和59%;间作条件下2个试验点分别增产1.2%和69%。优化施氮降低了水稻黄壳糯穗瘟的病情指数和发病率,单作条件下两个试验点较传统施肥分别下降13.4%,0.4%和40.6%,6.1%;间作条件下两个试验点较传统施肥分别下降34.8%,15.5%和44.3%,27.7%。     

Do Land Characteristics Affect Farmers' Soil Fertility Management?

Soil fertility management (SFM) has important implications for sustaining agricultural development and food self-sufficiency. Better understanding the determinants of farmers' SFM can be a great help to the adoption of effective SFM practices. Based on a dataset of 315 plots collected from a typical rice growing area of South China, this study applied statistical method and econometric models to examine the impacts of land characteristics on farmers' SFM practices at plot scale. Main results showed that in general land characteristics affected SFM behaviors. Securer land tenure arrangements facilitated effective practices of SFM through more diversified and more soil-friendly cropping pattern choices. Plot size significantly reduced the intensities of phosphorus and potassium fertilizer application. Given other factors, 1 ha increase in plot size might reduce 3.0 kg ha⁻¹ P₂O₅ and 1.8 kg ha⁻¹ K₂O. Plots far from the homestead were paid less attention in terms of both chemical fertilizers and manure applications. Besides, plots with better quality were put more efforts on management by applying more nitrogen and manure, and by planting green manure crops. Significant differences existed in SFM practices between the surveyed villages with different socio-economic conditions. The findings are expected to provide important references to the policy-making incentive for improving soil quality and crop productivity.     

Effects of mechanized deep placement of nitrogen fertilizer rate and type on rice yield and nitrogen use efficiency in Chuanxi Plain,China

This paper investigates the yield and nitrogen use efficiency (NUE) of machine-transplanted rice cultivated using mechanized deep placement of N fertilizer in the rice–wheat rotation region of Chuanxi Plain, China. It provides theoretical support for N-saving and improves quality and production efficiency of machine-transplanted rice. Using a single-factor complete randomized block design in field experiments in 2018 and 2019, seven N-fertilization treatments were applied, with the fertilizer being surface broadcast and/or mechanically placed beside the seedlings at (5.5±0.5) cm soil depth when transplanting. The treatments were: N0, no N fertilizer; U1, 180 kg N ha^–1 as urea, surface broadcast manually before transplanting; U2, 108 kg N ha^–1 as urea, surface broadcast manually before transplanting, and 72 kg N ha^–1 as urea surface broadcast manually on the 10th d after transplanting, which is not only the local common fertilization method, but also the reference treatment; UD, 180 kg N ha^–1 as urea, mechanically deep-placed when transplanting; M1, 81.6 kg N ha^–1 as urea and 38.4 kg N ha^–1 as controlled-release urea (CRU), mechanically deep-placed when transplanting; M2, 102 kg N ha^–1 as urea and 48 kg N ha^–1 as CRU, mechanically deep-placed when transplanting; M3, 122.4 kg N ha^–1 as urea and 57.6 kg N ha^–1 as CRU, mechanically deep-placed when transplanting. The effects of the N fertilizer treatments on rice yield and NUE were consistent in the 2 yr. With a N application rate of 180 kg ha^–1, compared with U2, the N recovery efficiency (NRE), N agronomic use efficiency (NAE) and yield under the UD treatment were 20.6, 3.5 and 1.1% higher in 2018, and 4.6, 1.7 and 1.2% higher in 2019, respectively. Compared with urea alone (U1, U2 or UD), the NRE, NAE and yield achieved by M3 (combined application of urea and controlled-release urea) were higher by 9.2–73.3%, 18.6–61.5% and 6.5–16.5% (2018), and 22.2–65.2%, 25.6–75.0% and 5.9–13.9% (2019), respectively. Compared with M3, the lower-N treatments M1 and M2 significantly increased NRE by 4.0–7.8% in 2018 and 3.1–4.3% in 2019, respectively. Compared with urea surface application (U1 or U2), the yield under the M2 treatment was higher by 4.3–12.9% in 2018 and 3.6–10.1% in 2019, respectively. Compared with U2, the NRE and NAE under the M2 treatment was higher by 36.9 and 36.3% in 2018, and 33.2 and 37.4% in 2019, mainly because of higher N uptake. There was no significant difference in the concentration of nitrate in the top 0–20 cm soil under U1, U2 and M2 treatments during the full heading and maturity stages. During the full heading stage, U2 produced the highest concentration of nitrite in 0–20 cm and 20–40 cm soil among the N fertilizer treatments. In conclusion, mechanized deep placement of mixed urea and controlled-release urea (M2) at transplanting is a highly-efficient cultivation technology that enables increased yield of machine-transplanted rice and improved NUE, while reducing the amount of N-fertilization applied.     

Optimized nitrogen application methods to improve nitrogen use efficiency and nodule nitrogen fixation in a maize-soybean relay intercropping system

In China, the abuse of chemical nitrogen(N) fertilizer results in decreasing N use efficiency(NUE), wasting resources and causing serious environmental problems. Cereal-legume intercropping is widely used to enhance crop yield and improve resource use efficiency, especially in Southwest China. To optimize N utilization and increase grain yield, we conducted a two-year field experiment with single-factor randomized block designs of a maize-soybean intercropping system(IMS). Three N rates, NN(no nitrogen application), LN(lower N application: 270 kg N ha–1), and CN(conventional N application: 330 kg N ha–1), and three topdressing distances of LN(LND), e.g., 15 cm(LND1), 30 cm(LND2) and 45 cm(LND3) from maize rows were evaluated. At the beginning seed stage(R5), the leghemoglobin content and nitrogenase activity of LND3 were 1.86 mg plant–1 and 0.14 m L h–1 plant–1, and those of LND1 and LND2 were increased by 31.4 and 24.5%, 6.4 and 32.9% compared with LND3, respectively. The ureide content and N accumulation of soybean organs in LND1 and LND2 were higher than those of LND3. The N uptake, NUE and N agronomy efficiency(NAE) of IMS under CN were 308.3 kg ha–1, 28.5%, and 5.7 kg grain kg–1 N, respectively; however, those of LN were significantly increased by 12.4, 72.5, and 51.6% compared with CN, respectively. The total yield in LND1 and LND2 was increased by 12.3 and 8.3% compared with CN, respectively. Those results suggested that LN with distances of 15–30 cm from the topdressing strip to the maize row was optimal in maize-soybean intercropping. Lower N input with an optimized fertilization location for IMS increased N fixation and N use efficiency without decreasing grain yield.     

Developing sustainable summer maize production for smallholder farmers in the North China Plain: An agronomic diagnosis method

With an increasing population and changing diet structure, summer maize is increasingly becoming an important energy crop in China. However, traditional farmer practices for maize production are inefficient and unsustainable. To ensure food security and sustainable development of summer maize production in China, an improved, more sustainable farmer management system is needed. Establishing this system requires a comprehensive understanding of the limitations of current farming practice and the ways it could be improved. In our study, 235 plots from three villages in the North China Plain(NCP) were monitored. Maize production on farms was evaluated; our results showed that the maize yield and nitrogen partial factor productivity(PFP_N) were variable on smallholder farms at 6.6~(–1)3.7 t ha~(–1) and 15.4–88.7 kg kg~(–1), respectively.Traditional farming practices also have a large environmental impact(nitrogen surplus: –64.2–323.78 kg ha~(–1)). Key yield components were identified by agronomic diagnosis. Grain yield depend heavily on grain numbers per hectare rather than on the 1 000-grain weight. A set of improved management practices(IP) for maize production was designed by employing a boundary line(BL) approach and tested on farms. Results showed that the IP could increase yield by 18.4% and PFP_N by 31.1%, compared with traditional farmer practices(FP), and reduce the nitrogen(N) surplus by 57.9 kg ha~(–1). However,in terms of IP effect, there was a large heterogeneity among different smallholder farmers' fields, meaning that, precise technologies were needed in different sites especially for N fertilizer management. Our results are valuable for policymakers and smallholder farmers for meeting the objectives of green development in agricultural production.     

Closing the nitrogen use efficiency gap and reducing the environmental impact of wheat-maize cropping on smallholder farms in the Guanzhong Plain,Northwest China

A high crop yield with the minimum possible cost to the environment is generally desirable. However, the complicated relationships among crop production, nitrogen (N) use efficiency and environmental impacts must be clearly assessed. We conducted a series of on-farm N application rate experiments to establish the linkage between crop yield and N₂O emissions in the Guanzhong Plain in Northwest China. We also examined crop yield, partial factor productivity of applied N (PFPN) and reactive N (Nr) losses through a survey of 1 529 and 1 497 smallholder farms that grow wheat and maize, respectively, in the region. The optimum N rates were 175 and 214 kg ha^–1 for winter wheat and summer maize, respectively, thereby achieving the yields of 6 799 and 7 518 kg ha^–1, correspondingly, with low N₂O emissions based on on-farm N rate experiments. Among the smallholder farms, the average N application rates were 215 and 294 kg ha^–1 season^–1, thus producing 6 490 and 6 220 kg ha^–1 of wheat and maize, respectively. The corresponding PFPN values for the two crops were 36.8 and 21.2 kg N kg^–1, and the total N₂O emissions were 1.50 and 3.88 kg ha^–1, respectively. High N balance, large Nr losses and elevated N₂O emissions could be explained by the overdoses of N application and low grain yields under the current farming practice. The crop yields, N application rates, PFPN and total N₂O for wheat and maize were 18 and 24% higher, 42 and 37% less, 75 and 116% higher, and 42 and 47% less, correspondingly, in the high-yield and high-PFPN group than in the average smallholder farms. In conclusion, closing the PFPN gap between the current average and the value for the high-yield and high-PFPN group would increase crop production and reduce Nr losses or the total N₂O emissions for the investigated cropping system in Northwest China.     

Effects of nitrogen application rates and irrigation regimes on grain yield and water use efficiency of maize under alternate partial root-zone irrigation

Faced with the scarcity of water resources and irrational fertilizer use, it is critical to supply plants with water and fertilizer in a coordinated pattern to improve yield with high water use efficiency (WUE). One such method, alternate partial root-zone irrigation (APRI), has been practiced worldwide, but there is limited information on the performance of different irrigation regimes and nitrogen (N) rates under APRI. The objectives of this study were to investigate the effects of varying irrigation regimes and N rates on shoot growth, grain yield and WUE of maize (Zea mays L.) grown under APRI in the Hexi Corridor area of Northwest China in 2014 and 2015. The three N rates were 100, 200 and 300 kg N ha⁻¹, designated N₁, N₂ and N₃, respectively. The three irrigation regimes of 45–50%, 60–65% and 75–80% field capacity (FC) throughout the maize growing season, designated W₁, W₂ and W₃, respectively, were applied in combination with each N rate. The results showed that W₂ and W₃ significantly increased the plant height, stem diameter, crop growth rate, chlorophyll SPAD value, net photosynthetic rate (P_n), biomass, grain yield, ears per ha, kernels per cob, 1 000-kernel weight, harvest index, evapotranspiration and leaf area index (LAI) compared to W₁ at each N rate. The N₂ and N₃ treatments increased those parameters compared to N₁ in each irrigation treatment. Increasing the N rate from the N₂ to N₃ resulted in increased biomass and grain yield under W₃ while it had no impact on those under the W₁ and W₂ treatments. The W₃N₃ and W₂N₂ and W₂N₃ treatments achieved the greatest and the second-greatest biomass and grain yield, respectively. Increasing the N rate significantly enhanced the maximum LAI (LAI at the silking stage) and P_n under W₃, suggesting that the interaction of irrigation and fertilizer N management can effectively improve leaf growth and development, and consequently provide high biomass and grain yield of maize. The W₂N₂, W₂N₃ and W₃N₃ treatments attained the greatest WUE among all the treatments. Thus, either 60–65% FC coupled with 200–300 kg N ha⁻¹ or 75–80% FC coupled with 300 kg N ha⁻¹ is proposed as a better pattern of irrigation and nitrogen application with positive regulative effects on grain yield and WUE of maize under APRI in the Hexi Corridor area of Northwest China and other regions with similar environments. These results can provide a basis for in-depth understanding of the mechanisms of grain yield and WUE to supply levels of water and nitrogen.     

Significant reduction of ammonia emissions while increasing crop yields using the 4R nutrient stewardship in an intensive cropping system

Ammonia (NH₃) emissions should be mitigated to improve environmental quality.Croplands are one of the largest NH₃sources,they must be managed properly to reduce their emissions while achieving the target yields.Herein,we report the NH₃ emissions,crop yield and changes in soil fertility in a long-term trial with various fertilization regimes,to explore whether NH₃ emissions can be significantly reduced using the 4R nutrient stewardship (4Rs),and its int...     

密度与氮素互作对带状套作玉米产量的影响

为探究增密后对带状套作玉米产量的调控效应,分别设置种植模式、密度、施氮量三因素裂区田间试验,主因素为种植模式：带状套作玉米(A₁)和单作玉米(A₂),副因素为种植密度：60 000(B₁)和75 000株/hm²(B₂),副副因素为施氮水平：0(C₁)、225(C₂)、300(C₃)、375 kg/hm²(C₄),连续2年的短期定位大田试验,测定并分析各生育时期2种种植模式下玉米的产量、干物质积累、叶面积指数及叶绿素含量。结果表明,随着密度从60 000增至75 000株/hm²,单作和带状套作玉米分别增产5.36%和5.87%,带状套作玉米增产幅度较单作玉米高8.69%;在2种密度条件下,带状套作玉米施氮量达到300和375 kg/hm²时,产量较不施氮处理增加15.94%和14.28%,单作玉米施氮量达到225和300 k...     

施氮和木薯-花生间作对木薯养分积累和系统养分利用的影响

【目的】木薯-花生间作是一种生态高效的种植模式,研究分析施氮和木薯-花生间作对木薯氮磷钾素积累和系统氮磷钾素利用的影响规律,以期为木薯-花生合理间作和养分高效利用提供理论依据。【方法】试验于2015和2016年,以木薯品种华南205和花生品种粤油200为材料,设计不施氮、施氮2个水平和木薯单作、花生单作、木薯间作1行花生、木薯间作2行花生及木薯间作3行花生共5种种植模式,研究不同木薯-花生间作系统的木薯养分积累和系统养分利用特征。【结果】随着木薯生育时期的推进,块根氮磷钾素的积累量和分配率增加;茎秆氮磷钾素积累量和氮素分配率增加,磷钾素分配率先增加后降低;叶片氮磷钾素积累量先增加后降低,分配率下降。不同生育时期、不同施氮水平和不同种植模式间块根、茎秆、叶片和植株的氮磷钾素积累量变化规律存在差异。同一种植模式,施氮处理生产100 kg荚果所需氮钾量、生产100 kg鲜薯所需氮磷钾量、木薯氮素收获指数、木薯磷钾肥偏生产力、钾素间作优势、系统氮钾素积累总量和系统内木薯氮磷钾素比例较不施氮处理提高或显著提高,而花生氮钾素利用效率、花生磷素积累总量、木薯氮钾素利用效率、木薯钾素收获指数、系统内花生氮磷钾素比例、氮素间作优势和氮磷钾素的土地当量比较不施氮处理降低或显著降低。同一施氮水平,间作花生的氮磷素积累总量、氮磷钾肥偏生产力显著低于单作花生,间作木薯的氮磷钾肥偏生产力、钾素利用效率和磷素收获指数低于单作木薯。随着间作花生行数的增加,氮磷钾素的土地当量比和间作优势、系统内花生氮磷钾素比例、花生的氮磷钾素积累总量和氮磷钾肥偏生产力提高或显著提高,系统内木薯氮磷钾素比例下降。【结论】与单作模式相比,木薯间作2行和3行花生模式虽降低了系统内单一作物的产量、氮磷钾肥偏生产力和氮磷钾素积累总量,但提高了系统氮磷钾素积累总量,表现出明显的间作优势,氮磷钾素间作优势分别为63.91—112.11、19.37—42.67和68.29—105.62 kg·hm~(-2)。     

The potential of green manure to increase soil carbon sequestration and reduce the yield-scaled carbon footprint of rice production in southern China

Green manure (GM) has been used to support rice production in southern China for thousands of years. However, the effects of GM on soil carbon sequestration (CS) and the carbon footprint (CF) at a regional scale remain unclear. Therefore, we combined the datasets from long-term multisite experiments with a meta-analysis approach to quantify the potential of GM to increase the CS and reduce the CF of paddy soils in southern China. Compared with the fallow–rice practice, the GM–rice practice increased the soil C stock at a rate of 1.62 Mg CO₂-eq ha^–1 yr^–1 and reduced chemical N application by 40% with no loss in the rice yield. The total CF varied from 7.51 to 13.66 Mg CO₂-eq ha^–1 yr^–1 and was dominated by CH₄ emissions (60.7–81.3%). GM decreased the indirect CF by 31.4% but increased the direct CH₄ emissions by 19.6%. In the low and high CH₄ emission scenarios, the CH₄ emission factors of GM (EF_gc) were 5.58 and 21.31%, respectively. The greater soil CS offset the increase in GM-derived CF in the low CH₄ scenario, but it could not offset the CF increase in the high CH₄ scenario. A trade-off analysis also showed that GM can simultaneously increase the CS and reduce the total CF of the rice production system when the EF_gc was less than 9.20%. The variation in EF_gc was mainly regulated by the GM application rates and water management patterns. Determining the appropriate GM application rate and drainage pattern warrant further investigation to optimize the potential of the GM–rice system to increase the CS and reduce the total CF in China.     

No-tillage effects on grain yield and nitrogen requirements in hybrid rice transplanted with single seedlings: Results of a long-term experiment

This study was conducted to determine whether, and if so how, the grain yield and nitrogen (N) requirements of hybrid rice transplanted as single seedlings are affected by no-tillage (NT) practices. A fixed field experiment was done at the Experimental Farm of Hunan Agricultural University in Changsha, Hunan Province, China, from 2004 to 2014. Grain yield and yield attributes (panicle number per m², spikelet number per panicle, spikelet filling percentage, grain weight, total biomass, and harvest index) were evaluated as well as the N-use characteristics (total N uptake, internal N-use efficiency, and N requirements) of hybrid rice transplanted as single seedlings comparing NT with conventional tillage (CT). A significant finding was that there were no significant differences in grain yield, yield attributes, and N-use characteristics between CT and NT. Averaged across the 11 years, grain yield and N requirements were 9.51 t ha^–1 and 20.2 kg t^–1 under CT and 9.33 t ha^–1 and 20.0 kg t^–1 under NT, respectively. There were significant yearly variations in grain yield, yield attributes, and N-use characteristics observed under both CT and NT. The yearly variation in grain yield was related to simultaneous changes in spikelet number per panicle, grain weight, total biomass, and harvest index. Also, it was found that grain yield was positively correlated with internal N-use efficiency but negatively correlated with N requirements. It is concluded that grain yield and N requirements in hybrid rice when transplanted as single seedlings are not affected adversely by NT. The results of this study suggest that (1) compatible relationships among yield attributes can be established in hybrid rice that is transplanted as single seedlings, and (2) higher grain yield and higher N-use efficiency can be concurrently achieved in hybrid rice transplanted as single seedlings.