Effect of rice straw biochar and irrigation on growth,dry matter yield and radiation-use efficiency of maize grown on an Acrisol in Ghana

In order to determine whether the current low productivity associated with rainfed cultivation on degraded soils in Ghana can be improved by biochar amendment and irrigation, field experiments with maize were conducted over two seasons in 2017 and 2018. Rice straw biochar at rates of 0 t/ha (B₀), 15 t/ha (B₁₅) and 30 t/ha (B₃₀) was combined with irrigation regimes of full irrigation (I₁₀₀), deficit irrigation (I₆₀) and no irrigation (I₀). The I₁₀₀ treatment was irrigated to field capacity every 3–4 days according to time domain reflectometry measurements while the I₆₀ treatment received 60% of the irrigation amount given to I₁₀₀ but with the same irrigation frequency. The I₀ treatment was not irrigated. In both seasons, the B₃₀ treatment recorded the highest total dry matter yield (TDMY), intercepted photosynthetically active radiation (IPAR) and radiation-use efficiency (RUE) and these were significantly (p ≤ .05) higher than B₀ except for RUE in 2017. Irrigation regimes did not significantly affect TDMY, IPAR and RUE in 2017 but compared to I₁₀₀, I₀ significantly reduced TDMY, IPAR and RUE in the relatively dryer 2018 season. Measured ratio vegetation indices differentiated biochar treatments earlier in the 2018 season than during 2017 and increase of leaf chlorophyll content indices with biochar rate in both seasons indicated that biochar amendment improved nitrogen uptake. Our study demonstrated that rice straw biochar is capable of increasing TDMY, IPAR and RUE of maize grown on degraded soils in Ghana. The study further showed that TDMY, IPAR and RUE of deficit irrigated maize for two seasons were similar to the counterpart fully irrigated maize and may be a viable water management option for farmers in Ghana to save irrigation water resources.     

Radiation‐Use Efficiency,Biomass Production,and Grain Yield in Two Maize Hybrids Differing in Drought Tolerance

Drought‐tolerant (DT) maize (Zea mays L.) hybrids have potential to increase yield under drought conditions. However, little information is known about the physiological determinations of yield in DT hybrids. Our objective was to assess radiation‐use efficiency (RUE), biomass production, and yield in two hybrids differing in drought tolerance. Field experiments were conducted in 2013 and 2014 with two hybrids, P1151HR (DT hybrid) and 33D49 (conventional hybrid) under well‐watered (I₁₀₀) and drought (I₅₀) conditions. I₁₀₀ and I₅₀ refer to 100 % and 50 % evapotranspiration requirement, respectively. On average, P1151HR yielded 11–27 % greater than 33D49 at I₁₀₀ and about 40 % greater at I₅₀, At I₁₀₀, greater yield in P1151HR was due to greater biomass at physiological maturity (BM_pm) resulting from greater post‐silking biomass accumulation (BM_post). At I₅₀, both hybrids had similar BM_pm but P1151HR showed a higher harvest index and greater BM_post. RUE differed significantly (P < 0.05) between the hybrids at I₁₀₀, but not at I₅₀. At I₁₀₀, the RUE values for P1151HR and 33D49 were 4.87 and 4.28 g MJ^?1 in 2013, and 3.71 and 3.48 g MJ^?1 in 2014. At I₅₀, the mean RUE was 3.89 g MJ^?1 in 2013 and 3.16 g MJ^?1 in 2014. Results indicate that BM_post is important for maintaining high yield in DT maize.     

Irrigation and Nutrient Effects on Growth and Water–Yield Relationship of Wheat (Triticum aestivum L.) in Central India

Increasing production of wheat from a limited water supply can result from efficient irrigation and nutrient management. A 3‐year field experiment was conducted at the Indian Institute of Soil Science, Bhopal, to study the growth, yield, seasonal evapotranspiration (ET) and water use efficiency (WUE), and the water–yield relationship of wheat in a soybean–wheat cropping system on vertisols. Three levels of irrigation, viz. I₀, no post‐sowing irrigation; I₁, two irrigations [crown root initiation (CRI) and flowering stage]; and I₂, three irrigations (CRI, maximum tillering and flowering stage) and three nutrient management treatments, viz. F₀, control (without fertilizer/manure); F₁, 100 % NPK (100–21.5–24.9 kg ha^?1); and F₂, 100 % NPK + farmyard manure (FYM‐10 t ha^?1) were tested in a split‐plot design with three replication. It has been established (through anova ) that the year effect was rather negligible and the interaction effects of irrigation and nutrient management on the growth parameters, ET, yield components, yield and WUE were significant. Plant height, progressive leaf area index, dry matter accumulation and crop growth rate were higher in I₂F₂, and I₂F₁ and I₁F₂ were statistically at par. The seasonal ET increased significantly with the increase in water supply in every nutrient treatment and it was highest in I₂F₂ and lowest in I₀F₀. The highest grain yield was obtained in I₂F₂; and a similar yield was recorded in I₃F₁ and I₂F₂. This shows a strong interaction effect between irrigation and nutrients. Yield components, viz. number of ears m^?2, number of grains ear^?1 and 1000‐grain weight were significant. The higher number of ears m^?2 containing greater number of grains with relatively heavier weights appeared to have contributed to the higher yield in I₁F₂, I₂F₁ and I₂F₂. The highest WUE obtained in I₀F₂ did not correspond to the highest yield and maximum ET, but a WUE of 10.43 kg ha^?1 mm^?1 in the I₂F₂ combination corresponded with the highest yield and the seasonal ET requirement was 391.8, which was 137 % greater than the water use at maximum WUE. The ET–grain yield relationship was linear, with a lowest regression slope (i.e. marginal WUE) and elasticity of water production (E_wp) in F₀ and a considerably higher slope and E_wp in F₁ and F₂. As the E_wp is positive and close to one in 100 % NPK treatment, the scope of improving WUE and yield with only inorganic fertilizer is very little, and relatively greater scope exists in the integrated management of organic manure and inorganic fertilizer. The results suggest that integrated nutrient management (100 % NPK + FYM) in conjunction with three irrigations maximized yield of wheat with concomitant improvement in ET and WUE under limited water availability.     

Nitrogen‐, water‐ and radiation‐use efficiencies affected by sugarcane breeding in Argentina

This study aimed to identify whether and how sugarcane (Saccharum spp.) breeding in Argentina modified nitrogen‐use efficiency (NUE), water‐use efficiency (WUE) and radiation‐use efficiency (RUE). Thirteen varieties were grown in two consecutive seasons. Trends in different traits were estimated by fitting the data to linear or bilinear regression models. There was a linear increase in NUE and WUE with the year of release throughout the 70‐year span, whereas water use was not modified by sugarcane breeding. There was a positive and strong (r > 0.90; P < 0.01) association between NUE and WUE and between sugar yield and NUE or WUE. Although RUE was not modified by sugarcane breeding, the amount of radiation intercepted by the crop increased with the year of release. Modern varieties had a higher maximum interception and needed fewer days to reach maximum interception than old varieties. This study suggests that applying ecophysiological knowledge would be instrumental in sugarcane breeding programmes in order to develop varieties with high resource‐use efficiency and capable to adapt to global climate change.     

Shade Effects on Phaseolus vulgaris L. Intercropped with Zea mays L. under Well-Watered Conditions

Field experiments were carried out under unstressed conditions of soil water during two summer crop growing seasons (1998–99 and 1999–2000 seasons) in a South African semi‐arid region (Bloemfontein, Free State, South Africa). The aim of this study was to investigate shade effects on beans intercropped with maize in terms of plant mass and radiation use. The experimental treatments were two cropping systems (no shading/sole cropping and shading/intercropping) and two row orientations (north–south and east–west). At the top of bean canopies shaded by maize, incident radiation was reduced by up to 90 %. Shading reduced total dry matter of beans by 67 % at the end of the growing season, resulting in yield losses. The dry matter partitioning into leaf and stem (the ratios of leaf and stem to total biomass) was about 50 % higher in intercropping than sole cropping. In contrast, intercropped beans had 40 % lower dry matter partitioning into pod (the ratio of pod to total biomass). Fraction of radiation intercepted by sole‐cropped beans steeply increased until canopy closure (0.9) and then slowly decreased, while fraction of radiation intercepted by intercropped beans remained constant between 0.0 and 0.2 throughout the growing seasons. However, intercropped beans had 77 % higher radiation use efficiency (RUE) than sole‐cropped beans. In contrast, for maize, no effect of intercropping (shading) was found on growth, partitioning, yield, radiation interception or RUE. Consequently, lower bean yield losses can be attained in association with late shading rather than early shading. This can be controlled by growing crops with different temporal and spatial treatments. As regards row treatment, no effect of row direction was found on growth, partitioning, yield, radiation interception or RUE.     

Light interception and radiation use efficiency in temperate quinoa (Chenopodium quinoa Willd.) cultivars

Sea level quinoas are grown at low altitudes in Central and Southern Chile. Both sensitivity to photoperiod and response to temperature largely determine quinoa adaptation, but crop biomass production must be quantified to evaluate agronomic performance. The objectives of this work are: (i) to characterize development effects on leaf area evolution for genotypes of sea level quinoa differing in cycle length, (ii) to quantify the extinction coefficient (k) for photosynthetically active radiation (PAR) and radiation use efficiency (RUE) from emergence up to the beginning of grain filling and (iii) to identify which crop attributes related to canopy architecture should be considered to improve biomass production. Four cultivars (NL-6, RU-5, CO-407 and Faro) were cropped in Pergamino (33°56′S, 60°35′W, 65 m a.s.l.), Argentina, at three densities (from 22 to 66 plants m⁻²) in two consecutive years under field conditions with adequate water and nutrient supply. Thermal time to first anthesis and maximum leaf number on the main stem were linearly correlated (r² = 0.87; p < 0.0001). Leaf area continued to increase during the flowering phase, notably in NL-6, the earliest genotype. There were significant differences in maximum plant leaf area between cultivars. Increasing density reduced plant leaf area but effects were comparatively small. Estimated k was 0.59 ± 0.02 across genotypes and was higher (p < 0.05) for 66 plants m⁻². Values for RUE changed as cumulative intercepted PAR (IPAR) increased; at initial stages of development RUE was 1.25 ± 0.09 g MJ IPAR⁻¹, but if cumulative IPAR was higher than 107.5 ± 10.4 MJ IPAR m⁻², RUE was 2.68 ± 0.15 g MJ IPAR⁻¹. That change occurred when leaf area index (LAI) and fraction of PAR intercepted were still low and ranged from 0.61 to 1.38 and from 0.33 to 0.51, respectively. No significant association was found with any developmental stage. Our results agreed to the notion that RUE variation during pre-anthesis phases is largely determined by LAI through its effect on radiation distribution within the canopy. Biomass production could be improved if periods of interception below 50% of incoming PAR were reduced to ensure high RUE. This seems to be possible in temperate areas both by the use of late genotypes with a higher number of leaves on the main stem and by early genotypes provided adequate plant density is chosen. Early increment in LAI and overlapping of the leaf area increase period with the flowering phase are desirable strategies for earliest genotypes to maximize yield.     

土壤水分对冬小麦生长后期光能利用及水分利用效率的影响

通过控制不同土壤水分条件形成不同的小麦（Triticum aestivum L.）群体结构,测定了抽穗到成熟期间小麦冠层光合有效辐射（PAR）截获及垂直分布、干物质积累和产量。研究表明,不同处理小麦冠层对PAR的截获量差异较小（小于15.7%）,但冠层上部（60~80 cm）的PAR截获量和生长后期PAR转化效率差异明显（100.7%和63.7%）,与产量和光能利用效率变化一致,可见土壤水分是通过改变小麦群体内PAR垂直分布及PAR转化效率对作物产量和光能利用效率产生影响。抽穗到成熟期间维持小麦冠层上部PAR截获率在50%左右是实现高产的重要保证。随着土壤水分改善,冬小麦光能利用率和产量持续增加,但水分利用效率却先于二者提前降低,说明改善水分利用效率是提高华北地区农业气候资源利用效率的关键。在底墒充足的条件下,分别在拔节和挑旗期灌水60 mm可获得较高的光能和水分利用效率及经济产量     

Drought Tolerance and Water‐Use Efficiency of Biogas Crops: A Comparison of Cup Plant,Maize and Lucerne‐Grass

The cup plant (Silphium perfoliatum L.) is discussed as an alternative energy crop for biogas production in Germany due to its ecological benefits over continuously grown maize. Moreover, a certain drought tolerance is assumed because of its intensive root growth and the dew water collection by the leaf cups, formed by fused leaf pairs. Therefore, the aim of this study was to estimate evapotranspiration (ET ), water‐use efficiency (WUE ) and the relevance of the leaf cups for the cup plant's water balance in a 2‐year field experiment. Parallel investigations were conducted for the two reference crops maize (high WUE ) and lucerne‐grass (deep and intensive rooting) under rainfed and irrigated conditions. Root system performance was assessed by measuring water depletion at various soil depths. Transpiration‐use efficiency (TUE ) was estimated using a model approach. Averaged over the 2 years, drought‐related above‐ground dry matter reduction was higher for the cup plant (33 %) than for the maize (18 %) and lucerne‐grass (14 %). The WUE of the cup plant (33 kg ha^?1 mm^?1) was significantly lower than for maize (50 kg ha^?1 mm^?1). The cup plant had a lower water uptake capacity than lucerne‐grass. Cup plant dry matter yields as high as those of maize will only be attainable at sites that are well supplied with water, be it through a large soil water reserve, groundwater connection, high rainfall or supplemental irrigation.     

玉米水分利用效率、碳稳定同位素判别值和叶面积之间的关系

通过盆栽试验,研究了水分胁迫对玉米各生育期叶面积(LA)、比叶面积(SLA)、水分利用效率(WUE)和碳稳定同位素判别值(Δ¹³C)的影响以及不同水分条件下WUE、茎叶Δ¹³C和SLA之间的关系。试验设4个水分处理, 分别为田间持水量的75%~100%(W1)、50%~75%(W2)、30%~50%(W3)和0~30%(W4)。W2和W3处理对生物量干重的影响在玉米拔节期明显,而W4处理导致各生育期生物量干重的极大降低。在W2和W3处理下,玉米各生育期的WUE随着水分胁迫程度的增加而增加;而W4处理下,WUE在孕穗期后则显著降低。SLA在孕穗期达到最大。玉米各生育期叶片Δ¹³C在W1、W2和W3处理中呈随水分胁迫的增加而降低的趋势,而W4处理下的叶片Δ¹³C则高于W2和W3处理。玉米叶片光合同化物质往茎秆转移时没有发生碳同位素的分馏作用。在玉米的各生育期,叶片Δ¹³C、茎秆Δ¹³C和玉米WUE呈一致性的负相关;各生育期的SLA与Δ¹³C呈正相关关系,而与WUE呈显著的负相关。     

不同熟期夏玉米品种籽粒灌浆与脱水特性及其密度效应

研究不同熟期夏玉米品种籽粒灌浆与脱水特性及种植密度的调控作用, 以期为黄淮海地区夏玉米籽粒机收提供科学依据。2016—2017年在山东农业大学玉米科技创新园, 种植早熟玉米品种登海518 (DH518)、衡早8号(HZ8)和中晚熟玉米品种郑单958 (ZD958)、登海605 (DH605), 设60 000、75 000、90 000株 hm ^-23个种植密度。结果表明, 早熟品种DH518、HZ8较中晚熟品种ZD958、DH605灌浆期短, 产量低。4个品种生理成熟时的籽粒含水率与其生育期相关性不显著, 早熟品种籽粒后期脱水速率快, DH518和HZ8从籽粒达最大含水量到生理成熟的脱水速率均值较ZD958和DH605两年分别高0.015% °C ^-1和0.014% °C ^-1。相关性分析显示, 籽粒脱水速率与灌浆速率相关性不显著, 生育后期籽粒含水率与茎鞘、叶片含水率呈显著正相关, 与苞叶、穗轴含水率呈极显著正相关。随种植密度的增加, 不同品种籽粒灌浆期缩短, 平均灌浆速率降低, 籽粒生理成熟时的含水率降低。合理增加种植密度能够显著提高不同熟期夏玉米品种的产量。     

Radiation use efficiency,chemical composition,and methane yield of biogas crops under rainfed and irrigated conditions

For biomethane production, the cup plant (Silphium perfoliatum L.) is considered a promising alternative substrate to silage maize (Zea mays L.) due to its high biomass potential and associated ecological and environmental benefits. It has also been suggested to grow cup plant on less productive soils because of its presumed drought tolerance, but robust information on the impact of water shortage on biomass growth and substrate quality of cup plant is rare. Therefore, this study assesses the effects of soil water availability on the chemical composition and specific methane yield (SMY) of cup plant. Furthermore above-ground dry matter yield (DMY) was analysed as a function of intercepted photosynthetic active radiation (PAR) and radiation use efficiency (RUE). Data were collected in a two-year field experiment under rainfed and irrigated conditions with cup plant, maize, and lucerne-grass (Medicago sativa L., Festuca pratensis Huds., Phleum pratense L.). The cup plant revealed a slight decrease of −6% in the SMY in response to water shortage (less than 50% of plant available water capacity). The average SMY of cup plant [306 l (kg volatile solids (VS))⁻¹] was lower than that of maize [362 l (kg VS)⁻¹] and lucerne-grass [334 l (kg VS)⁻¹]. The mean drought-related reduction of the methane hectare yield (MHY) was significantly greater for cup plant (−40%) than for maize (−17%) and lucerne-grass (−13%). The DMY reduction in rainfed cup plant was mainly attributed to a more severe decrease in RUE (−29%) than for maize (−16%) and lucerne-grass (−12%). Under water stress, the mean cup plant RUE (1.3 g MJ⁻¹) was significantly lower than that of maize (2.9 g MJ⁻¹) and lucerne-grass (1.4 g MJ⁻¹). Compared to RUE, the reduced PAR interception was less meaningful for DMY in rainfed crops. Hence, the cup plant is not suitable for growing on drought prone lands due to its high water demand required to produce reasonably high MHYs.     

不同栽培模式对旱地春玉米光合特性和水分利用率的影响

明确旱地春玉米高产与水分高效协调的栽培技术及其生理原因,对提高水分限制条件下玉米水分利用效率及玉米可持续生产具有重要意义。本文以郑单958为材料,于2010年和2011年在陕西长武进行大田试验,设置当地农户栽培(对照)、高产高效栽培、超高产栽培和再高产高效栽培等4种栽培模式,比较了其对春玉米光合特性和水分利用效率的影响。结果表明,当地农户栽培、高产高效栽培、超高产栽培和再高产高效栽培产量平均达7.7、9.2、11.7和10.6 t hm^-2,高产模式较对照产量分别提高20.1%、52.9%和37.7%,水分利用效率分别提高27.8%、60.9%和45.1%。与当地农户栽培相比,高产高效栽培、超高产栽培和再高产高效栽培提高了花后叶片净光合速率(P_n)、蒸腾速率(T_r)和单叶水分利用效率(WUE_L);相对电子传递速率(ETR)、PSII实际量子产额(Φ_PSII)和光化学猝灭(q_P);延缓了叶片衰老;花后干物质积累量分别增加29.0%、82.3%和56.1%。结果说明通过地膜覆盖、增加密度和氮肥运筹等关键栽培技术的集成与优化,可实现旱地春玉米高产与水分高效30%以上的目标;其增产增效的主要原因在于显著增强玉米花后叶片光捕获能力与光化学效率,延缓叶片早衰,促进花后干物质积累及其对籽粒的贡献率。     

Modelling Biomass Accumulation and Partitioning in Chickpea (Cicer arietinum L.)

Quantitative information regarding biomass accumulation and partitioning in chickpea (Cicer arietinum L.) is limited or inconclusive. The objective of this study was to obtain baseline values for extinction coefficient (K_S), radiation use efficiency (RUE, g MJ^?1) and biomass partitioning coefficients of chickpea crops grown under well‐watered conditions. The stability of these parameters during the crop life cycle and under different environmental and growth conditions, caused by season and sowing date and density, were also evaluated. Two field experiments, each with three sowing dates and four plant densities, were conducted during 2002–2004. Crop leaf area index, light interception and crop biomass were measured between emergence and maturity. A K_S value of 0.5 was obtained. An average RUE of 1 g MJ^?1 was obtained. Plant density had no effect on RUE, but some effects of temperature were detected. There was no effect of solar radiation or vapour pressure deficit on RUE when RUE values were corrected for the effect of temperature. RUE was constant during the whole crop cycle. A biphasic pattern was found for biomass partitioning between leaves and stems before first‐seed stage. At lower levels of total dry matter, 54 % of biomass produced was allocated to leaves, but at higher levels of total dry matter, i.e. under favourable and prolonged conditions for vegetative growth, this portion decreased to 28 %. During the period from first‐pod to first‐seed, 60 % of biomass produced went to stems, 27 % to pods and 13 % to leaves. During the period from first‐seed to maturity, 83 % of biomass was partitioned to pods. It was concluded that using fixed partitioning coefficients after first‐seed are not as effective as they are before this stage. Environmental conditions (temperature and solar radiation) and plant density did not affect partitioning of biomass.     

氮肥后移对玉米间作豌豆耗水特性的调控效应

针对水资源不足严重制约干旱灌区间作发展,间作中以氮调水理论研究的薄弱,生产实践中缺乏氮肥运筹同步提高间作产量和水分利用效率的措施等问题。2012-2013年,以河西走廊规模化应用的玉米间作豌豆为研究对象,在总施氮量相同且基肥和孕穗肥分别占10%和50%条件下,设氮肥后移30% (N₁,拔节肥0+花粒肥40%)、氮肥后移15% (N₂,拔节肥15%+花粒肥25%)、传统制度(N₃,拔节肥30%+花粒肥10%) 3个施氮处理,探讨氮肥后移对间作产量和水分利用效率(WUE)的影响,以期为禾豆间作优化施氮制度、提高产量和水分利用效率提供理论依据。结果表明,氮肥后移对玉米间作豌豆总耗水量(ET)影响不显著,但降低了棵间蒸发量(E)和棵间蒸发量占总耗水量的比例(E/ET);与传统施氮处理相比,氮肥后移15%使玉米间作豌豆的E和E/ET降低6%和4%,氮肥后移30%使玉米间作豌豆的E和E/ET均降低2%。在间作系统中,豌豆带、玉米带的棵间蒸发量分别为329 mm、232 mm,表明豌豆带的无效耗水显著高于玉米带。氮肥后移15%间作的混合籽粒产量、WUE较传统施氮间作分别高出6%、5%,氮肥后移30%间作混合籽粒产量、WUE较传统施氮间作分别提高3%、2%。因此,玉米间作豌豆结合氮肥后移15%,即豌豆开花结荚期(玉米拔节期)追施氮肥67.5 kg hm^-2、玉米大喇叭口期追施氮肥225 kg hm^-2、玉米花后15 d追施氮肥112.5 kg hm^-2,可作为绿洲灌区玉米间作豌豆增产和提高WUE的农艺措施之一。     

Yield,water use and radiation use efficiencies of kenaf (Hibiscus cannabinus L.) under reduced water and nitrogen soil availability in a semi-arid Mediterranean area

Kenaf is a warm-season species that recently has been proved to be a good source of biomass for cellulose pulp for the paper industry in Mediterranean countries, where the use of hemp is problematic for legal reasons. A two-year research program aiming at studying the effects of different water regimes and nitrogen fertilization levels, upon plant growth, leaf area index, biomass accumulation, water and radiation use efficiency, was carried out on kenaf under a typically semi-arid Mediterranean climate of South Italy. In cv. Tainung 2, four different water regimes (I₀ = no irrigation, I₂₅, I₅₀ and I₁₀₀ = 25, 50 and 100% ETc restoration, respectively) and three nitrogen levels (N₀ = no nitrogen, N₇₅ and N₁₅₀ = 75 and 150 kg ha⁻¹ of N, respectively) were studied. The amount of water applied strongly affected plant growth (in terms of LAI, plant height and biomass) and final total and stem dry yield, which significantly increased from I₀ to I₁₀₀. Nitrogen did not exert any beneficial effect upon dry yield. Radiation Use Efficiency (RUE), calculated in the second year only, was the highest (1.95 g DM MJ⁻¹) in fully irrigated treatment (I₁₀₀) and the lowest (0.86 g DM MJ⁻¹) in the dry control.Water use efficiency (WUE) was rather similar among water regimes, whilst irrigation water use efficiency (IWUE) progressively increased with the decrease of total volume of water distributed to the crop by irrigation, from 3.47 to 12.45 kg m⁻³ in 2004 and from 4.27 to 7.72 kg m⁻³ in 2005. The results obtained from this research demonstrate that in semi-arid areas of South Italy, irrigation at a reduced rate (50% ETc restoration) may be advantageous, since it allowed a 42–45% irrigation water saving, when compared to the fully irrigation treatment, against a 23% (in 2004) and 36% (in 2005) yield reduction, and a still good efficiency (near that potential) in transforming the solar radiation in dry biomass was maintained (RUE = 1.76 g DM MJ⁻¹, against 1.95 g DM MJ⁻¹ in fully irrigated treatment).     

Moisture Stress Effects on the Yield and Water Use of Sorghum Hybrids and their Parents*

Little is known of the relationship between hybrids and parental material with respect to water use and drought resistance. Responses of sorghum (Sorghum bicolor [L.] Moench) F₁ hybrids to moisture deficits are partially determined by parental material. The yield and water use of six sorghum hybrids and their respective male and female parents were evaluated under stressed and well irrigated conditions during 1980 and 1981 at Tucson, Arizona. The soil was Comoro loamy sand (coarse-loamy, mixed, calcareous, thermic typic Torrifluvent) with an average available soil moisture of 16 % at field capacity. Changes in soil moisture were monitored semi-weekly by neutron modulation. Meteorological data were collected daily. The 1980 season had higher maximum temperatures and pan evaporation than the 1981 season. Differences in cumulative water use among entries were apparent within the same water treatments during 1981. Mean cumulative evapotranspiration (ET) for the stressed treatment was 248 and 281 mm for 1980 and 1981, respectively, and ET under well irrigated conditions was 419 and 528 mm for 1980 and 1981, respectively. Hybrids produced greater grain yield than their parents under both water treatments. This was due to greater seed number for hybrids. Seed numbers were more stable for hybrids over both treatments than for parents. Hybrids four and seven had the greatest grain yield in 1980 and 1981, respectively, under stressed conditions. Water use efficiency (WUE) was significantly different within water treatments but was not so between the irrigated and stressed treatments. Hybrids WUE was generally greater than that of parents except for hybrid five under irrigated conditions in 1981. Hybrids with WUE and stable yields were not necessarily reflective of parental material under stressed and non-stressed environments.     

玉米杂交种水分利用效率及相关性状分析

为充分发挥玉米杂交种的水分利用效率,实现玉米高产、高效的目的,本研究以中国生产和推广应用的玉米杂交种为材料,在多变低水条件下,根据成熟期产量水分利用效率剖析其高效性。研究结果表明,不同玉米杂交种间其水分利用效率存在较大的变异范围,玉米杂交种水分利用效率存在着丰富多样的类型;水分利用效率相关性状方差分析结果表明,产量水分利用效率各构成性状在品种间存在着较大差异,不同玉米品种可利用不同性状达到水分的高效利用;简单相关和偏相关分析结果表明,与水分利用效率密切相关的性状是穗行数、行粒数和百粒重。因此,在生产应用中应因地制宜选用不同玉米杂交种,在品种选育过程中应重视相关性状的选择。     

西北绿洲灌区水氮耦合对燕麦品种陇燕3号耗水特性及产量的影响

灌水和施肥,尤其是施氮肥,是调控作物生长和增加产量的两大重要技术措施,其互作是燕麦高产高效栽培中重要因素。2014—2015年连续2个生长季,在甘肃河西绿洲灌区的田间试验设3个定额灌溉和3个施氮(纯氮)水平,研究水氮耦合对陇燕3号农田0~150 cm土层耗水量、棵间蒸发、产量及水分利用效率的影响。3个灌溉处理的灌水量分别为270 mm(I_1)、337.5 mm(I_2)和405 mm(I_3),3个施氮水平分别为90 kg hm~(–2)(N_1)、120 kg hm~(–2)(N_2)和150 kg hm~(–2)(N_3)。从播种到成熟,燕麦阶段耗水强度呈先增后减趋势,抽穗至灌浆是最大耗水期,且同一施氮水平下,阶段耗水强度随灌水量增大而显著增加。在全生育期内,棵间蒸发量(E)及土壤水分蒸发量占总蒸发量的比例(E/ET)表现先降后升趋势,且相同施氮量下,拔节至灌浆期随灌水量的增大而增大,而灌浆至成熟期则随灌水量的增大而减小。相同施氮量下,燕麦产量随灌水量增加而显著增加,水分利用效率却随灌水量增加而降低。产量N_3I_3最高(5466.0~5727.5 kg hm~(–2)),N_3I_2次之(5428.5~5678.5 kg hm~(–2)),N_1I_1最低(4504.5~4804.3 kg hm~(–2));水分利用效率N_3I_2最大(12.11~12.82 kg mm~(–1) hm~(–2)),N_3I_1次之(12.04~12.63 kg mm~(–1) hm~(–2)),N_1I_3最小(9.79~10.58 kg mm~(–1) hm~(–2))。由此表明,水氮耦合对燕麦水分利用及产量具有显著互作效应。施氮量150 kg hm~(–2)、灌溉定额337.5 mm是西北绿洲灌区燕麦种植较佳的节水、高产水氮管理模式。     

覆盖对夏玉米产量及水分利用效率的影响

研究不同土壤水分状况下秸秆覆盖对夏玉米生长发育指标、产量和水分利用效率的影响。试验在防雨棚下的测坑中进行,设计了秸秆覆盖和土壤水分控制下限（占田间持水率的75%,65%和55%）两个因素,分析夏玉米生长指标、产量及水分利用效率的变化规律。结果表明,秸秆覆盖对夏玉米生长发育有促进作用,在不同的水分状况下,覆盖处理的夏玉米叶面积指数、产量和水分利用效率均优于不覆盖处理。中水分条件覆盖处理下的夏玉米产量较对照条件下的高水分夏玉米产量无显著降低,而且其水分利用效率最高。建议在夏玉米覆盖生产方式中采用中水分灌溉方式,可以达到节水高产的目的。     

Diurnal and Seasonal Light Transmission to Cowpea in Sorghum–Cowpea Intercrops in Mali

Tall cereal–short legume intercropping is ubiquitous in the semiarid tropics of West Africa, yet little is known regarding the dynamics of light interception in these systems. A field study was conducted in Cinzana, Mali, to characterize light transmission to cowpea in sorghum [Sorghum bicolor (L.) Moench]–cowpea [Vigna unguiculata (L.) Walp] intercropping systems. Different sorghum–cowpea planting configurations were used to examine photosynthetically active radiation (PAR) incident on the cowpea. The 4‐m tall sorghum cultivar CSM 219E intercepted > 60 % of incoming PAR from 2 m height to harvest (50 days). Consequently, total seasonal PAR received by intercropped cowpea was 60–66 % that of the unshaded monocrop. Thirty‐minute averages of PAR transmitted around solar noon had poor agreement (R²=0.53) with fractional daily light interception and overestimated seasonal PAR received by cowpea by 17 % in the north–south row orientation used. Thirty‐minute averages at 1100 h (R²=0.93) and 1430 h (R²=0.91) had the closest correlation to diurnal average PAR incident on cowpea. This study indicates that tall guineense sorghum captures significant amounts of light at low leaf area index (LAI) (< 2.0). Row orientation, time of measurement, plant height and LAI should be considered in calculating light interception in these intercropping systems.