减氮对甜玉米//大豆间作系统大豆结瘤固氮特性的影响

为了探讨减氮和甜玉米//大豆间作对大豆结瘤和固氮特性的影响,通过大田定位试验(2015年春-2018年秋,共8季)对比了三种施氮水平:不施氮(N0,0 kg·hm^(-2))、减量施氮(N1,300 kg·hm^(-2))、常规施氮(N2,360 kg·hm^(-2)),两种间作模式:甜玉米//大豆2∶3间作(S2B3)、甜玉米//大豆2∶4间作(S2B4),以及不施肥单作大豆(SB)对大豆结瘤数、根瘤干重、固氮效率和固氮量及其稳定性的影响。结果表明:1)大豆根瘤数、根瘤干重、固氮效率和固氮量随着年季变化呈现明显的动态变化,春季大豆根瘤数和根瘤干重显著高于秋季,但秋季固氮效率和固氮量显著高于春季。2)施氮水平与种植模式极显著影响大豆固氮效率和固氮量,不施肥处理大豆固氮效率为S2B4(69.87%)>S2B3(60.64%)、SB(56.3%),但生物固氮量为SB(142.31 kg·hm^(-2))>S2B4(109.50 kg·hm^(-2))>S2B3(86.12 kg·hm^(-2))。3)间作甜玉米显著提高了大豆的固氮效率且随大豆种植比例的增加而增加,S2B4-N0、N1及N2的固氮效率分别比S2B3-N0、N1及N2高9.47%、3.41%、1.83%,但是,相同施氮水平下不同间作模式之间均无差异。4)减氮和间作甜玉米可显著提高大豆固氮率和固氮量的稳定性。总之,减氮和间作甜玉米均能促进大豆结瘤、提高生物固氮量及固氮效率。

减氮对华南地区甜玉米//大豆间作系统产量稳定性的影响

在广东省广州市华南农业大学试验中心,通过大田定位试验(2013年秋2017年秋5年9季)对比了两种施氮水平[减量施氮(300 kg hm 2,N1)和常规施氮(360 kg hm 2,N2)]、4种种植模式[甜玉米单作(SS)、甜玉米//大豆2∶3间作(S2B3)、甜玉米//大豆2∶4间作(S2B4)、大豆单作(SB)]的甜玉米、大豆及系统产量的动态变化,采用W^2(Wricke’s ecovalence,生态价值指数)、变异系数(CV)和可持续指数(SYI)评价了产量的时间稳定性,旨在为华南地区一年2熟制甜玉米产区地力保育和绿色生产提供科学依据。结果表明:1)各处理甜玉米、大豆和系统总产量呈现明显的生产季节动态变化,不同年季、种植模式对甜玉米、大豆和系统总产量均有极显著影响,施氮水平仅显著影响甜玉米的产量。2)所有间作处理甜玉米的相对产量均高于单作,间作系统的实际产量损失指数(AYLs)均大于零,表明甜玉米//大豆间作能稳定地保持间作优势且显著提高了土地利用效率。3)不同处理甜玉米产量的W^2、CV和SYI均没有显著差异,但单作大豆的W^2值显著高于间作,单作大豆的产量稳定性低于间作大豆。种植模式对系统总产量稳定性有显著影响,且间作大豆提高了其稳定性。4)间作大豆显著提高了土壤地力贡献率,S2B3和S2B4的平均地力贡献率分别为75.07%和74.27%,比SS分别高30.29和29.47个百分点。5)与单作甜玉米相比,9季甜玉米//大豆间作显著提高了土壤pH,缓解了长期大量施氮导致的土壤酸化对地力的影响。连续减量施氮没有影响甜玉米//大豆间作系统土壤有机质和全量养分含量,300kg·hm^-2的施氮量能够满足甜玉米和大豆对氮素的需要。减量施氮与间作大豆是华南甜玉米产区资源高效利用、系统产量稳定的可持续绿色生产模式。

减量施氮与间作大豆对华南地区甜玉米农田氮平衡的影响

本文在广东广州华南农业大学试验中心,通过大田定位试验(2015—2016年两年4季)对比了两种施氮水平[减量施氮(300 kg·hm^(-2),N1)和常规施氮(360 kg·hm^(-2),N2)]、3种种植模式[甜玉米单作(SS)、甜玉米//大豆2∶3间作(S2B3)、甜玉米//大豆2∶4间作(S2B4)]农田生态系统的氮素输入、输出和平衡状况,旨在为减少化学氮肥投入水平,提高氮素利用效率,在华南地区发展环境友好型的玉米可持续生产模式提供科学依据。结果表明:1)减量施氮与甜玉米//大豆间作降低了系统氮素总输入量,大豆固氮和秸秆还田降低了化肥氮输入的比重,与常规施氮相比,减量施氮下SS、S2B3和S2B4的化肥氮输入占年均氮素总输入的比例分别下降3.24%、3.64%和3.77%。2)间作大豆增加了系统籽粒氮素累积量,N1和N2处理甜玉米//大豆间作的年均籽粒氮素累积量分别是单作甜玉米的2.43倍和2.18倍;减量施氮与甜玉米//大豆间作能降低甜玉米农田氮素损失,N1和N2处理甜玉米//大豆间作的年均氨挥发量分别比单作甜玉米低39.02%和27.26%;间作甜玉米的氮淋溶量比单作低13.85%。3)减量施氮与间作大豆显著降低了系统氮素盈余量,S2B3-N1、S2B3-N2和S2B4-N1、S2B4-N2年均氮素盈余量分别为71.03 kg·hm^(-2)、133.7 kg·hm^(-2)和42.87 kg·hm^(-2)、100.64 kg·hm^(-2),分别比SS处理N1和N2的平均值减少81.27%、64.75%和88.69%、73.47%。因此,减量施氮甜玉米//大豆间作模式能维持系统作物产量、减少生产成本、降低环境污染风险,具有较高的经济和生态效益。

减量施氮与间作大豆对甜玉米土壤团聚体及有机碳含量的影响

【目的】探究不同氮水平与间作大豆对甜玉米土壤团聚体稳定性及有机碳含量的影响,为优化甜玉米//大豆带状复合种植技术体系、实现氮肥减量增效和农田固碳减排提供科学依据。【方法】依托甜玉米//大豆间作长期定位试验研究了施氮水平(N0-不施氮,N1-减量施氮300 kg/hm^(2)和N2-常规施氮360 kg/hm^(2))和种植模式(SS-甜玉米单作、S2B3-甜玉米//大豆2∶3间作和S2B4-甜玉米//大豆2∶4间作)对甜玉米产量、土壤团聚体以及有机碳含量的影响。【结果】施氮显著提高了甜玉米产量并降低了土地当量比,N1和N2处理的降幅分别为11.30%~14.59%和9.66%~10.73%,但减量施氮和常规施氮间无显著差异;施氮促进粗大团聚体(>2 mm)分解为细大团聚体(0.25~2 mm),显著降低甜玉米土壤团聚体稳定性、原土及各粒级团聚体有机碳含量和粗大团聚体有机碳贡献率。总体上,间作对土壤团聚体稳定性、原土及团聚体土壤有机碳含量无显著影响;但S2B3模式有提高甜玉米土壤团聚体稳定性的趋势,且在N0处理下S2B3处理的土壤有机碳含量显著高于其他处理。【结论】施氮显著降低了甜玉米//大豆间作系统土壤团聚体稳定性及有机碳含量,减量施氮与甜玉米//大豆2∶3间作在维持甜玉米产量稳定的同时有提高土壤团聚体稳定性和有机碳固持的潜力。

低磷红壤无机磷组分特征及间作调控作用

为明确间作和施用磷肥对低磷红壤无机磷组分的影响,促进酸性土壤磷肥高效利用,通过田间小区定位试验,采用玉米单作(MM)、玉米//大豆间作(MI)2种种植模式,在4个施磷水平(P2O50、60、90、120 kg·hm^(-2),分别记作P0、P60、P90、P120)下,研究玉米//大豆间作根际土壤无机磷组分变化特征,探讨间作对红壤玉米产量及其可持续性、磷吸收和磷素收支平衡、土壤无机磷组分的调控作用。结果表明,玉米籽粒产量及其可持续性指数(SYI)、磷吸收量随着施磷水平的增加而增加,在P90水平达到最大值。低磷红壤无机磷组分以O-P和Fe-P为主,二者占无机磷库的71.44%~80.18%,施用磷肥显著提高了红壤Fe-P和Al-P的含量与占比。玉米//大豆间作显著提高玉米产量,促进磷的吸收利用,减少土壤磷素盈余量,显著降低红壤O-P、Fe-P、Al-P含量。与单作相比,在P60、P90、P120水平下,间作玉米产量分别显著提高66.70%、52.44%、74.14%,SYI分别显著提高55.31%、42.18%、78.00%,磷吸收量分别显著提高61.97%、48.67%、74.33%,土壤磷盈余量分别显著降低33.39%、27.27%、17.06%。相较于单作,间作红壤中有效磷含量无显著差异,而O-P和Al-P含量在P0、P60、P90、P120水平下分别显著降低20.62%、16.79%、16.62%、18.48%和21.98%、21.08%、20.19%、20.18%,Fe-P含量在P60、P90、P120水平下分别显著降低19.37%、15.78%、17.72%。低磷供应(P0和P60)间作与单作红壤Ca-P含量无显著差异,在P90和P120水平下,间作红壤Ca-P含量降低23.50%和26.70%。随机森林模型分析表明,间作体系下,红壤Fe-P和Al-P是磷吸收的关键无机磷组分,间作总方差解释度较单作提高了7.95%。综上,在低磷红壤上,合理间作通过促进红壤中难溶性无机磷组分的活化增加玉米的磷吸收,具有减少土壤磷素固定、提高玉米产量及其可持续性的潜力。

Analysis on Waxy Corn/Soybean Intercropping Pattern and Economic Benefit

The research mainly analyzed effects of waxy corn/soybean intercropping on yields of the two crops, as well as agronomic characters, and the economic benefits of the mode. The results showed that although yields of waxy corn and soybean went down by 21.19% and 31.04% per unit area, land equivalent ratio（1.48） kept higher than 1, suggesting the intercropping improves land use rate. Besides, due to the practice of intercropping, many characters of waxy corn grew, but of soybean declined. The economic benefits from high to low were waxy corn/soybean intercropping, monoculture of waxy corn, and monoculture of soybean.

Effects of Intercropping Patterns on Dry Matter Accumulation and Transportation of Maize(Zea mays L.) and Soybean[Glycine max(L.) Merrill]

[Objective] The aim was to discuss the group dry matter accumulation and economic benefits under the patterns of intercropping maize （Zea mays L.） with soy-bean [Glycine max （L.） Merril ]. [Methods] Zhengdan-958 and Luhuang-1 were used as the testing breeds to study the effects of intercropping patterns on dry matter accumulation and transportation of maize and soybean in Huang-huai-hai. [Results] For maize, the dry matter accumulation amounts per hectare of intercropping was significant higher than that of the monoculture patterns, especial y after silking, when it reached extremely level; while for soybean, the dry matter accumulation amounts before flowering and after flowering of monocropping were al significantly higher than that of the intercropping patterns. For both maize and soybean, the transfer amounts of monocropping were al significantly or extremely significantly higher than that of intercropping; and the transfer ratio of maize intercropping was 0.59% higher than that of maize monocropping, while for soybean, it was 4.74% higher. Fitted dry matter accumulation with Logistic equation, it showed that the difference in maximum dry matter accumulation rate between maize monocropping and intercropping reached significant level, while for soybean, the maximum dry matter accumulation rate and its appearance time as wel as duration time between intercropping and monocropping were al reached significant level. The total land equivalent ratio of intercropping was 1.30. From yield and output value, the total yield of intercropping were 10.97 t/hm2, 0.64% and 326.85% higher than monocropping of maize and soy-bean, respectively. The total output value of intercropping was 25 796.23 yuan/hm2, respectively 12.67% and 104.68% higher than of maize and soybean monocropping. [Conclusion] The study lays a basis for improving grain yield and economic benefits.

The Effectiveness of Coccinellids as Natural Enemies of Aphids in Maize, Beans and Cowpeas Intercrop

A field study was conducted in Busia district of Kenya to elucidate the dynamics of ladybirds in mixed stands of maize, beans and cowpeas to determine their efficacy as sole control measures for Aphids. Maize, beans and cowpeas were intercropped using conventional husbandry practices and the general Coccinellid quantified as follows： Colonies of four Coccinellids, starved for 12 hours to enhance feeding on Aphids were assessed. The effects of weather on the abundance of Coccinellids were also investigated and involved collection of meteorological data from the Busia District Agricultural Office （BDAO） and from Busia Farmers Training Centre （BFTC） and relating them to the abundance and predation values. The predator population was most abundant in the mixed stands of maize and beans （2.33 predators/30 Aphids） as compared to their occurrence in pure stands of cowpeas （0.85 predators/30 Aphids）. The genus Cheilomenes spp. was the most ubiquitous predator with a mean of 4.00 individuals/30 Aphids while Hippodamia variegata was the least abundant predator species with a mean of 0.92 individuals/30 Aphids in all the agro-ecosystems. The larvae of Hippodamia variegata were the most bio-efficient, consuming 32.44 Aphids while their adults were the least bio-efficient, consuming 4.22 individuals for a period of 12 hours. The Coccinellids consumed more Aphids at higher aphid densities （24.05 Aphids） than at lower aphid densities （9.44 Aphids） over the same period of time. Rainfall and relative humidity had significant （F = 3.675; P 〈 0.05） effects on the abundance of Coccinellids. Temperature had significant （F = 3.58; P 〈 0.05） effect on the abundance of Coccinellids though at a lower level. Rainfall （r = -0.162） and relative humidity （r = - 0.084） were both inversely correlated with the abundance of Coccinellids. On the other hand, temperature was positively correlated （r = 0.159） with the prevalence of Coccinellids indicating that warmer and drier conditions favoured their multiplication.