Responses of rainwater conservation, precipitation-use efficiency and grain yield of summer maize to a furrow-planting and straw-mulching system in northern China

In the rain-fed areas of northern China, maize (Zea mays L.) is a main field crop, as it is well adapted to high temperatures and bright sunshine. However, low and variable rainfall and high evapotranspiration rates are common in water-limited environments during the growing season, and often mismatched rainfall events with the critical growth stages, making yield unstable. In this study, the performance of a furrow-planting and straw-mulching system was compared with the conventional flat-planting system in a double-crop culture of winter wheat (Triticum aestivum L.) and summer maize for two consecutive years (2005-2006 and 2006-2007). The four tested treatments were: conventional flat planting (F), furrow planting between ridges (B), flat planting with wheat straw-mulching (FS), and furrow planting between ridges with wheat-straw mulch (BS). Soil water content and leaf area index (LAI) were measured throughout the growing season each year, and grain yield and precipitation-use efficiency (PUE_Y) were determined.On average, ridge tillage combined with furrow planting increased maize yield by 430 kg ha⁻¹ (7.3%) and PUE_Y by 10.7% (1.5 kg ha⁻¹ mm⁻¹), compared with the conventional flat planting; furrow planting coupled with straw mulching increased yield by an additional 16.9% and PUE_Y by 19.4%, respectively. From jointing to maturity, LAI values of BS were significantly higher than those of F-system (55.6% vs. 26.1% in 2006 and 81.4% vs. 21.7% in 2007). Our data suggest that maize production adopted by furrow planting with straw-covered ridges performed best under seasonal average rainfall below 480 mm, which was associated with better synchronization of seasonal soil water supply and crop needs, leading to improved maize yield and PUE_Y.     

Dryland maize yields and water use efficiency in response to tillage/crop stubble and nutrient management practices in China

Rainfed crop production in northern China is constrained by low and variable rainfall. This study explored the effects of tillage/crop residue and nutrient management practices on maize (Zea mays L.) yield, water use efficiency (WUE), and N agronomic use efficiency (NAE) at Shouyang Dryland Farming Experimental Station in northern China during 2003–2008. The experiment was set-up using a split-plot design with 3 tillage/crop residue methods as main treatments: conventional, reduced (till with crop residue incorporated in fall but no-till in spring), and no-till (with crop residue mulching in fall). Sub-treatments were 3 NP fertilizer rates: 105–46, 179–78 and 210–92 kg N and P ha⁻¹. Maize grain yields were greatly influenced by the growing season rainfall and soil water contents at sowing. Mean grain yields over the 6-year period in response to tillage/crop residue treatments were 5604, 5347 and 5185 kg ha⁻¹, under reduced, no-till and conventional tillage, respectively. Grain yields under no-till, were generally higher (+19%) in dry years but lower (−7%) in wet years. Mean WUE was 13.7, 13.6 and 12.6 kg ha⁻¹ mm⁻¹ under reduced, no-till, and conventional tillage, respectively. The no-till treatment had 8–12% more water in the soil profiles than the conventional and reduced tillage treatments at sowing and harvest time. Grain yields, WUE and NAE were highest with the lowest NP fertilizer application rates (at 105 kg N and 46 kg P ha⁻¹) under reduced tillage, while yields and WUE tended to be higher with additional NP fertilizer rates under conventional tillage, however, there was no significant yield increase above the optimum fertilizer rate. In conclusion, maize grain yields, WUE and NAE were highest under reduced tillage at modest NP fertilizer application rates of 105 kg N and 46 kg P ha⁻¹. No-till increased soil water storage by 8–12% and improved WUE compared to conventional tillage, thus showing potentials for drought mitigation and economic use of fertilizers in drought-prone rainfed conditions in northern China.     

Growing maize in clumps as a strategy for marginal climatic conditions

Under dryland conditions of the Texas High Plains, maize (Zea mays) production is limited by sparse and erratic precipitation that results in severe water stress particularly during grain formation. When plant populations are reduced to 2.0–3.0 plants m⁻² to conserve soil water for use during grain filling, tillers often form during the vegetative growth and negate the expected economic benefit. We hypothesized that growing maize in clumps spaced 1.0 m apart would reduce tiller formation, increase mutual shading among the plants, and conserve soil water for grain filling that would result in higher grain yield. Studies were conducted during 2006 and 2007 at Bushland, TX. with two planting geometries (clump vs. equidistant), two irrigation methods (low-energy precision applicator, LEPA, and low-elevation spray applicator, LESA) at three irrigation levels (dryland, 75 mm and 125 mm in 2006; and dryland, 50 mm and 100 mm in 2007). For dryland plots in 2007, clump plants had only 0.17 tillers (0.66 tillers m⁻²) compared with 1.56 tillers per plant (6.08 tillers m⁻²) for equidistant spacing. Tillers accounted for 10% of the stover for the equidistant plants, but less than 3% of the grain. Clump planting produced significantly greater grain yields (321 g m⁻² vs. 225 g m⁻² and 454 g m⁻² vs. 292 g m⁻² during 2006 and 2007, respectively) and Harvest Indexes (0.54 vs. 0.49 and 0.52 vs. 0.39 during 2006 and 2007, respectively) compared with equidistant plants in dryland conditions. Water use efficiency (WUE) measurements in 2007 indicated that clumps had a lower evapotranspiration (ET) threshold for initiating grain production, but the production function slopes were 2.5 kg m⁻³ for equidistant treatments compared to 2.0 kg m⁻³ for clump treatments. There was no yield difference for method of irrigation on water use efficiency. Our results suggest that growing maize in clumps compared with equidistant spacing reduced the number of tillers, early vegetative growth, and Leaf Area Index (LAI) so that more soil water was available during the grain filling stage. This may be a useful strategy for growing maize with low plant populations in dryland areas where severe water stress is common.     

陇中旱塬不同覆盖集雨种植方式对春玉米生长特性和产量的影响

以春玉米"金凯3号"为供试材料,2015年和2016年开展两年6个不同处理大田试验,设置平地全膜覆盖(WM)、平地半膜覆盖(HM)、隔沟覆膜垄播(MRM)、全膜双垄沟播(WRF)、垄沟秸秆覆盖(SM)和露地平播(CK)6个处理,测定春玉米不同生育阶段生长特性、收获后产量、水分利用效率(WUE)及经济效益等指标。结果表明,覆盖集雨种植方式均能显著促进春玉米生长和干物质积累,提高产量、水分利用效率和经济效益。较露地平作(CK),WRF和MRM处理玉米产量和WUE分别提高了4 561.34、4 126.31 kg/hm2和14.48、12.72 kg/(hm2·mm),以全膜双垄沟播种植方式增幅最显著。试验结果表明,WRF处理纯收益最高,达5 878.26元/hm2,WM处理次之,为4 599.18元/hm2,分别较CK处理增加5 113.3 1和3 834.23元/hm2,可显著提高投入产出比。全膜双垄沟播春玉米种植由于其良好耕作生产特性,是陇中旱塬春玉米高产、稳产的优势选择。     

半干旱区不同秋覆盖方式对农田土壤水温效应及玉米水分利用效率的影响

2013～2015年在黄土高原半干旱区以传统平作不覆盖为对照(CK)、地膜全覆盖(PA)、可降解膜全覆盖(BA)、玉米秸秆全覆盖(SA)和沟垄集雨半膜覆盖(RH)4种覆盖方式,研究不同秋季覆盖方式的土壤水分保蓄效果及对春玉米生长的影响。结果表明,在冬春休闲期,PA、BA、SA、RH处理均能有效提高播种前土壤水分,SA和RH处理在整个生育期土壤蓄水量显著高于CK,PA和BA处理仅在生育前期有较高的土壤水分;PA、BA和RH处理均有增温效果。不同处理中,PA处理产量最高,2年平均较CK提高58.17%,RH与BA处理分别较CK提高34.16%和27.05%,SA处理低于CK;水分利用效率与产量规律一致,PA、BA和RH处理分别较CK提高36.89%、14.34%和29.51%。     

不同覆盖模式对玉米叶片水分利用效率的影响

采用常规耕作（T1）、秸秆覆盖（T2）、起垄覆膜膜侧种植（T3）、起垄无膜（T4）、无垄覆膜（T5）对玉米叶片光合作用和叶片水平上的水分利用效率以及产量和产量构成因素方面进行分析研究。结果表明,玉米叶片的净光合速率（P_n）、蒸腾速率（T_r）、气孔导度（Cond）、胞间二氧化碳浓度（C_i）和水分利用效率（WUE）在不同覆盖模式下均存在显著差异,且起垄覆膜膜侧种植模式下的P_n、Cond和WUE为最大,T_r和 C_i较低。叶片水分利用效率与净光合速率和气孔导度呈极显著正相关,相关系数分别为0.94、0.98;与蒸腾速率和胞间二氧化碳浓度呈显著负相关,相关系数分别为0.92、0.96。 2018 年 T3 处理产量最高,达 10 095 kg/hm²,较 T1、T2、T4、T5 处理分别高 23.18%、0.55%、19.32 %、3.71%;2019年T3处理产量最高,达10 248 kg/hm²,较T1、T2、T4、T5处理分别高21.84 %、12.47%、15.69%、6.03%。     

秸秆带状覆盖对旱地冬小麦产量及土壤水分的影响

为探讨西北半干旱雨养条件下秸秆带状覆盖麦田水分利用特征和增产效果,通过田间试验,以露地条播为对照(CK),研究了3种不同覆盖处理[秸秆带状覆盖常规条播(SM1)、秸秆带状覆盖宽幅条播(SM2)和全膜覆土穴播(PM)]对旱地冬小麦田土壤含水量、小麦产量和水分利用效率的影响。结果表明,秸秆带状覆盖和全膜覆土穴播均可显著改善小麦全生育期0~20cm以及开花前20~90cm土壤墒情,但开花后20~90cm以及全生育期90~200cm土壤墒情普遍不如CK。3种覆盖处理均能促进冬小麦对土壤贮水的利用,显著提高开花至成熟阶段的耗水量及其占总耗水量的比例。秸秆带状覆盖和全膜覆土穴播生育期耗水量分别比CK增加4.6%和7.6%。秸秆带状覆盖在孕穗前0~200cm土壤墒情与全膜覆土穴播无显著差异,孕穗期开始则好于全膜覆土穴播;全膜覆土穴播0~200cm土壤贮水消耗量显著高于秸秆带状覆盖,而开花至成熟阶段的耗水量及其占总耗水量的比例则略低于秸秆带状覆盖。3种覆盖处理均显著提高产量和水分利用效率,PM、SM1和SM2较CK分别增产36.8%、29.7%和27.5%,水分利用效率分别提高27.3%、23.9%和22.7%。产量与生育期耗水量呈显著正相关(r=0.97*)。覆盖处理中,全膜覆土穴播产量虽最高,但从产量、水分利用效率和经济效益角度综合考虑,秸秆带状覆盖优于全膜覆土穴播。因此认为,秸秆带状覆盖是一种更加高产高效、适宜在西北半干旱雨养区推广的覆盖种植方式。     

Potato growth with and without plastic mulch in two typical regions of Northern China

Plastic film mulching is an important agricultural practice to save water and improve crop productivity in Northern China. Three field experiments were conducted to examine the effect of plastic mulch on soil temperature, potato (Solanum tuberosum L.) growth and evapotranspiration under drip irrigation in two typical regions of Northern China in 2001 and 2006. Results suggest that daily mean soil temperature under mulch was 2–9 °C higher than without mulch, especially during the early growth. Potato growth was restrained under mulching conditions in the North China Plain mainly due to the higher air temperature in this region and thus the higher soil temperature. The negative effects of mulching included a lower emergence and fewer marketable tubers per plant. Evapotranspiration and potato tuber yield were both reduced by mulch, especially in the North China Plain. In northwest China, mulch favorably increased the weight of jumbo tubers (W ≥ 300 g) per plant. Mulching duration had little effect on potato evapotranspiration in northwest China. However, both tuber yield and water use efficiency (WUE) decreased with increases in mulch duration, which suggests the plastic mulch should be removed early.     

土壤水分与覆盖对夏玉米生长及水分利用效率的影响

在防雨棚下的测坑中,采用裂区试验设计,研究土壤高水分(75%田间持水量,下同)、中水分(65%)和低水分(55%)条件下地膜覆盖、秸秆覆盖和不覆盖对夏玉米生长发育、产量性状和水分利用效率的影响。结果表明,在不同土壤水分条件下,地膜覆盖、秸秆覆盖处理的株高和叶面积指数均高于不覆盖的处理;在玉米生长前期地膜覆盖处理的株高和叶面积指数最高,在玉米生长的中后期秸秆覆盖处理的株高和叶面积指数最高。地膜和秸秆覆盖均具有显著的增产作用,与不覆盖相比,平均分别增产8.89%和22.26%。水分利用效率(WUE)随着土壤水分的降低而增加;在相同的土壤水分条件下,秸秆覆盖处理的WUE最高,地膜覆盖的次之,不覆盖的最低;当土壤水分控制下限为田间持水量的65%时,覆盖处理的节水增产效果最好,其中地膜和秸秆覆盖处理产量比不覆盖处理分别增加12.69%和28.47%,WUE分别提高21.78%和34.65%。     

半干旱地区玉米覆膜方式研究

干旱是制约玉米生产的主要因子。试验研究7种不同覆膜方式的土壤含水量、土壤温度、玉米生育期、农艺性状及产量,探求不同覆膜方式对半干旱地区玉米产量的影响。结果表明,顶凌覆膜优于春覆膜,全地面覆膜优于半覆膜平铺,其中全膜顶凌双垄沟栽培模式产量达到12 691.9 kg/hm2,较普通种植模式增产46.10%,较裸地种植增产77.98%,是一项适合半干旱地区的玉米高产栽培技术。     

Effect of winter cover crop species and planting methods on maize yield and N availability under irrigated Mediterranean conditions

Under semiarid Mediterranean conditions irrigated maize has been associated to diffuse nitrate pollution of surface and groundwater. Cover crops grown during winter combined with reduced N fertilization to maize could reduce N leaching risks while maintaining maize productivity. A field experiment was conducted testing two different cover crop planting methods (direct seeding versus seeding after conventional tillage operations) and four different cover crops species (barley, oilseed rape, winter rape, and common vetch), and a control (bare soil). The experiment started in November 2006 after a maize crop fertilized with 300 kg N ha⁻¹ and included two complete cover crop-maize rotations. Maize was fertilized with 300 kg N ha⁻¹ at the control treatment, and this amount was reduced to 250 kg N ha⁻¹ in maize after a cover crop. Direct seeding of the cover crops allowed earlier planting dates than seeding after conventional tillage, producing greater cover crop biomass and N uptake of all species in the first year. In the following year, direct seeding did not increase cover crop biomass due to a poorer plant establishment. Barley produced more biomass than the other species but its N concentration was much lower than in the other cover crops, resulting in higher C:N ratio (>26). Cover crops reduced the N leaching risks as soil N content in spring and at maize harvest was reduced compared to the control treatment. Maize yield was reduced by 4 Mg ha⁻¹ after barley in 2007 and by 1 Mg ha⁻¹ after barley and oilseed rape in 2008. The maize yield reduction was due to an N deficiency caused by insufficient N mineralization from the cover crops due to a high C:N ratio (barley) or low biomass N content (oilseed rape) and/or lack of synchronization with maize N uptake. Indirect chlorophyll measurements in maize leaves were useful to detect N deficiency in maize after cover crops. The use of vetch, winter rape and oilseed rape cover crops combined with a reduced N fertilization to maize was efficient for reducing N leaching risks while maintaining maize productivity. However, the reduction of maize yield after barley makes difficult its use as cover crop.     

Soil type,management history and current resource allocation: Three dimensions regulating variability in crop productivity on African smallholder farms

Soil fertility varies markedly within and between African smallholder farms, both as a consequence of inherent factors and differential management. Fields closest to homesteads (homefields) typically receive most nutrients and are more fertile than outlying fields (outfields), with implications for crop production and nutrient use efficiencies. Maize yields following application of 100 kg N ha⁻¹ and different rates and sources of P were assessed on homefields and outfields of smallholder farms in Zimbabwe. Soil organic carbon, available P and exchangeable bases were greater on the homefields than outfields. In each of three experimental seasons, maize yields in homefield control plots were greater than in the outfields of farms on a granitic sandy and a red-clay soil. Application of mineral N significantly increased maize yields on homefields in the first season (2.1–3.0 t ha⁻¹ on the clay soil and 1.0–1.5 t ha⁻¹ on the sandy soil) but the effects of N alone were not significant on the outfields due to other yield-limiting factors. Greatest yields of about 6 t ha⁻¹ were achieved on the clayey homefield with 100 kg N ha⁻¹ and 30 kg P ha⁻¹ applied as single super phosphate (SSP). Manure application gave greater yields (3–4 t ha⁻¹) than SSP (2–3 t ha⁻¹) in the sandy homefield and in the clayey outfield. Maize did not respond significantly to N, dolomitic lime, manure and P on the sandy outfield in the first and second seasons. In the third season, manure application (∼17 t manure ha⁻¹ year⁻¹) on the sandy outfield did result in a significant response in grain yields. Apparent P recovery in the first season was 55–65% when P was applied at 10 kg ha⁻¹ on the clayey homefield (SSP), clayey outfield (SSP and manure) and sandy homefield (manure) with apparent P recovery less than 40% when P was applied at 30 kg ha⁻¹. On the sandy outfield, P recovery was initially poor (<20%), but increased in the successive seasons with manure application. In a second experiment, less than 60 kg N ha⁻¹ was required to attain at least 90% of the maximum yields of 2–3 t ha⁻¹ on the sandy homefield and clayey outfield. N use efficiency varied from >50 kg grain kg⁻¹ N on the infields, to less than 5 kg grain kg⁻¹ N on the sandy outfields. Apparent N recovery efficiency by maize was greatest at small N application rates with P applied. We conclude that blanket fertilizer recommendations are of limited relevance for heterogeneous smallholder farms. Targeted application of mineral fertilizers and manure according to soil type and past management of fields is imperative for improving crop yields and nutrient use efficiencies.     

Phosphorus efficiency in long-term (15 years) wheat–maize cropping systems with various soil and climate conditions

Long-term (over 15 years) winter wheat (Triticum aestivum L.)–maize (Zea mays L.) crop rotation experiments were conducted to investigate phosphorus (P) fertilizer utilization efficiency, including the physiological efficiency, recovery efficiency and the mass (the input–output) balance, at five sites across different soil types and climate zones in China. The five treatments used were control, N, NP, NK and NPK, representing various combinations of N, P and K fertilizer applications. Phosphorus fertilization increased average crop yield over 15 years and the increases were greater with wheat (206%) than maize (85%) across all five sites. The wheat yield also significantly increased over time for the NPK treatments at two sites (Xinjiang and Shanxi), but decreased at one site (Hunan). The P content in wheat was less than 3.00 g kg⁻¹ (and 2.10 g kg⁻¹ for maize) for the N and NK treatments with higher values for the Control, NP and NPK treatments. To produce 1 t of grain, crops require 4.2 kg P for wheat and 3.1 kg P for maize. The P physiological use efficiency was 214 kg grain kg⁻¹ P for wheat and 240 kg grain kg⁻¹ P for maize with over 62% of the P from P fertilizer. Applying P fertilizer at 60–80 kg P ha⁻¹ year⁻¹ could maintain 3–4 t ha⁻¹ yields for wheat and 5–6 t ha⁻¹ yields for maize for the five study sites across China. The P recovery efficiency and fertilizer use efficiency averaged 47% and 29%, respectively. For every 100 kg P ha⁻¹ year⁻¹ P surplus (amount of fertilizer applied in excess of crop removal), Olsen-P in soil was increased by 3.4 mg P kg⁻¹. Our study suggests that in order to achieve higher crop yields, the long-term P input–output balance, soil P supplying capacity and yield targets should be considered when making P fertilizer recommendations and developing strategies for intensively managed wheat–maize cropping systems.     

Effect of sowing date and rate on the yield and flavonolignan content of the fruits of milk thistle (Silybum marianum L. Gaertn.) grown on light soil in a moderate climate

In the moderate climate of Poland it is recommended that milk thistle (Silybum marianum L. Gaertn.) be grown on fertile soils. The plant, however, develops a strong root system, so a working hypothesis has developed that cultivation can be extended to light soils with periodic water deficits. The aim of the present research was to determine the effects of sowing milk thistle on light soil at different dates and rates on the achene yield and flavonolignan content. This experiment was carried out during 2004-2006 at the Mochelek Experiment Station of the University of Technology and Life Sciences in Bydgoszcz (53°13′ N; 17°51′ E). The average fruit yields were 1.23 t ha⁻¹; those of silymarin were 26.5 kg ha⁻¹. The moisture and thermal conditions during the research years caused the fruit yields to range from 0.55 to 1.68 t ha⁻¹ and silymarin yields from 13.3 to 35.4 kg ha⁻¹. Delaying sowing from early to mid-April increased the plant density and decreased numbers of inflorescences and fruits per inflorescence; as a result, no effect of sowing date on fruit yield was found. Delaying the sowing date increased silymarin content by about 0.4% and its yield by 5.3 kg ha⁻¹. Increasing the sowing rate from 12 to 24 kg ha⁻¹ resulted in a slight (40 kg ha⁻¹) but significant increase in achene yield; however, it did not affect the silymarin content. The average silymarin content in fruits was 2.18%. The ratio of silydianin to silychristin was 1:2.2, and the ratio of silydianin to the sum of silybinin and isosilybinin was 1:3.3.     

Early plastic mulching increases stand establishment and lint yield of cotton in saline fields

Row covering with polyethylene film (plastic mulching) is a common practice for improving emergence, plant growth and yield of cotton in China. This is usually applied after sowing (conventional mulching, CM), but pre-sowing evaporation in spring would cause accumulation of salts and moisture loss in the surface layer of saline soils. Two experiments were conducted in Yellow River delta from 2004 to 2005 and during 2006, respectively to determine if row covering with plastic film 30 d before sowing (early mulching, EM) supports better productivity of cotton than CM in saline fields. In the first experiment, we studied the effects of EM versus CM and no-mulching (NM), on soil microclimate, seedling physiology, cotton yield and earliness. The second experiment was conducted in seven sites to compare cotton yield between the two mulching systems. Results from the first experiment showed that both EM and CM could effectively improve stand establishment, plant growth, earliness and lint yield of cotton relative to NM control. However, compared with CM, EM increased stand establishment rate by 11.4% and plant biomass by 9.9% and lint yield by 7.1%. EM, relative to CM and NM, increased the photosynthesis (Pn) rate 6.8% and decreased malondialdehyde (MDA) concentration 7.4% and Na⁺ level 8%. These improvements were due mainly to delayed accumulation of salts, elevation of soil temperature and reduction of moisture loss with EM. The revenue from EM was higher than that from CM and NM, suggesting the increased yield by EM was enough compensate for additional costs. The multi-site experiment in 2006 showed that the yield advantage of EM over CM was not significant in two sites with lower salinity (ECe = ∼6 dS/m), but substantial (from 9 to 14%) in five sites with higher salinity (ECe = 10–12 dS/m). The overall results suggest that EM is a promising cotton production technique in the saline Yellow River Delta and other cotton-growing areas with similar ecologies.     

Indigenous legume fallows (indifallows) as an alternative soil fertility resource in smallholder maize cropping systems

Widening the range of organic nutrient resources, especially N sources, is a major challenge for improving crop productivity of smallholder farms in southern Africa. A study was conducted over three seasons to evaluate different species of indigenous legumes for their biomass productivity, N₂-fixation and residual effects on subsequent maize crops on nutrient-depleted fields belonging to smallholder farmers under contrasting rainfall zones in Zimbabwe. Under high rainfall (>800 mm yr⁻¹), 1-year indigenous legume fallows (indifallows), comprising mostly species of the genera Crotalaria, Indigofera and Tephrosia, yielded 8.6 t ha⁻¹ of biomass within 6 months, out-performing sunnhemp (Crotalaria juncea L.) green manure and grass (natural) fallows by 41% and 74%, respectively. A similar trend was observed under medium (650–750 mm yr⁻¹) rainfall in Chinyika, where the indifallow attained a biomass yield of 6.6 t ha⁻¹ compared with 2.2 t ha⁻¹ for natural fallows. Cumulatively, over two growing seasons, the indifallow treatment under high rainfall at Domboshawa produced biomass as high as 28 t ha⁻¹ compared with ∼7 t ha⁻¹ under natural fallow. The mean total N₂ fixed under indifallows ranged from 125 kg ha⁻¹ under soils exhibiting severe nutrient depletion in Chikwaka, to 205 kg ha⁻¹ at Domboshawa. Indifallow biomass accumulated up to 210 kg N ha⁻¹, eleven-fold higher than the N contained in corresponding natural fallow biomass at time of incorporation. Application of P to indifallows significantly increased both biomass productivity and N₂-fixation, translating into positive yield responses by subsequent maize. Differences in maize biomass productivity between indifallow and natural fallow treatments were already apparent at 2 weeks after maize emergence, with the former yielding significantly (P < 0.05) more maize biomass than the latter. The first maize crop following termination of 1-year indifallows yielded grain averaging 2.3 t ha⁻¹, significantly out-yielding 1-year natural fallows by >1 t ha⁻¹. In the second season, maize yields were consistently better under indifallows compared with natural fallows in terms of both grain and total biomass. The first maize crop following 2-year indifallows yielded ∼3 t ha⁻¹ of grain, significantly higher than the second maize crop after 1-year indifallows and natural fallows. The study demonstrated that indigenous legumes can generate N-rich biomass in sufficient quantities to make a significant influence on maize productivity for more than a single season. Maize yield gains under indifallow systems on low fertility sandy soils exceeded the yields attained with either mineral fertilizer alone or traditional green manure crop of sunnhemp.     

Reciprocal influence of crops and shallow ground water in sandy landscapes of the Inland Pampas

In regions with shallow water tables, ground water may have a positive (water supply) or negative (waterlogging or salinization) impact on crops. Reciprocally, crops can influence ground water, altering water table depth and chemical composition. We quantified these reciprocal influences along natural gradients of groundwater depth in flat sedimentary landscapes of the Inland Pampas occupied by wheat, soybean, and maize during two growing seasons (2006/2007 and 2007/2008). We correlated crop yield and groundwater depth maps at the field level and made direct plant, soil and groundwater observations at the stand level across topographic gradients. Water table level largely accounted for spatial crop yield variation, explaining 20–75% of their variance. An optimum groundwater depth range, where crop yields were highest, was observed for all three crop species analyzed (1.40–2.45 m for maize, 1.20–2.20 m for soybean, and 0.70–1.65 m for wheat). The areas within these optimum bands had yields that were 3.7, 3 and 1.8 times larger than those where the water table was below 4 m for wheat, maize, and soybean, respectively. As groundwater levels become shallower than these depth bands, crop yields declined sharply (∼0.05 kg m⁻² on average for every 10 cm increase in water table level), suggesting negative effects of waterlogging, root anoxia and/or salinity. Groundwater levels below these depth bands were associated with gradually declining yields, likely driven by poorer groundwater supply.     

春玉米行间覆膜田间土壤水分时空动态及水分高效利用机理研究

在不同覆膜方式下对春玉米田间土壤水分时空运移规律、耗水特征和水分利用效率进行了系统研究。结果表明:行间覆膜全生育期0～100cm土层土壤贮水量明显高于行上覆膜和不覆膜。不同覆膜方式下,春玉米全生育期土壤水分状况可分为土壤水分大量损耗期和土壤水分收支平衡期,且0～100cm土层可分为急变层、活跃层和相对稳定层;不同覆膜方式下膜内外土壤水分差异主要体现在0～60cm土层,行间覆膜使玉米根系长期生长在土壤含水量较高的区域,促进了玉米的生长发育和土壤水分的直接有效利用;不同覆膜方式的土壤水分利用效率、产量和产量水平的水分利用效率皆表现为行间覆膜>行上覆膜>不覆膜。行间覆膜较高的水分利用效率主要是充分有效地运用了降水和灌溉水。     

Yield, grain quality and water use efficiency of rice under non-flooded mulching cultivation

Plastic film or straw mulching cultivation under non-flooded condition has been considered as a new water-saving technique in rice production. This study aimed to investigate the yield performance in terms of quality and quantity and water use efficiency (WUE) under such practices. A field experiment across 3 years was conducted with two high-yielding rice cultivars, Zhendao 88 (a japonica cultivar) and Shanyou 63 (an indica hybrid cultivar) and four cultivation treatments imposed from transplanting to maturity: traditional flooding as control (TF), non-flooded plastic film mulching (PM), non-flooded wheat straw mulching (SM), and non-flooded no mulching (NM). Compared with those under the TF, root oxidation activity, photosynthetic rate, and activities of key enzymes in sucrose-to-starch conversion in grains during the grain filling period were significantly increased under the SM, whereas they were significantly reduced under the PM and NM treatments. Grain yield showed some reduction under all the non-flooded cultivations but differed largely among the treatments. The reduction in yield was 7.3–17.5% under the PM, 2.8–6.3% under the SM, and 39–49% under the NM. The difference in grain yield was not significant between TF and SM treatments. WUE for irrigation was increased by 314–367% under the PM, 307–321% under the SM, and 98–138% under the NM. Under the same treatment especially under non-flooded conditions, the indica hybrid cultivar showed a higher grain yield and higher WUE than the japonica cultivar. The SM significantly improved milling, appearance, and cooking qualities, whereas the PM or the NM decreased these qualities. We conclude that both PM and SM could significantly increase WUE, while the SM could also maintain a high grain yield and improve quality of rice. The SM would be a better practice than the PM in areas where water is scarce while temperature is favorable to rice growth, such as in Southeast China.     

Lucerne management in an organic farming system under dry site conditions

Biological nitrogen fixation (BNF) as a result of the legumes–rhizobia symbioses is the main source of nitrogen in organic farming systems. Lucerne (Medicago sativa L.), used as green manure or as forage legume, is important on arable farms under dry site conditions. In a field experiment on organically managed agricultural fields, we examined the impacts of the utilisation system (harvested = forage production versus mulched = green manure) and the crop composition (pure lucerne crops versus lucerne–grass mixtures) on yield, biological nitrogen fixation (BNF), soil inorganic N content, N balance and water consumption of autumn-cultivated lucerne crops. The study was conducted at the University of Natural Resources and Applied Life Sciences, Vienna, in eastern Austria—a region characterized by pannonian site conditions (9.8 °C mean annual temperature, 545 mm average total precipitation) and stockless farming systems. Our results indicate that the utilisation system and the crop composition had no marked influence on above- and below-ground dry matter (DM) and N yield, soil inorganic N contents, BNF, or water use efficiency of lucerne. The level of symbiotically fixed N₂ in harvested lucerne was 89–125 kg N ha⁻¹ (27–33% Ndfa = nitrogen derived from atmosphere) in the first year and 161–175 kg N ha⁻¹ (47–49% Ndfa) in the second year of the study. The high soil inorganic N supply in the first year increased the N uptake from soil by lucerne and led to a reduced BNF. Under the dry and unfavourable conditions in both study years, the nitrogen release from the legume mulch was retarded and BNF in mulched lucerne was not reduced. Assuming low gaseous N losses by mulching (15–30 kg N ha⁻¹), the green manure system reached a positive N balance (+137 to +186 kg N ha⁻¹) for the subsequent crops because abundant residues remained on the field.