Management strategies for sustainable yield of potato crop under high temperature

High temperature has a deleterious effect in productivity of cool season crops like potato. This study was conducted to assess the efficacy of soil management practices to high-temperature tolerance in potato. Two popularly grown potato cultivars of northeast India, Kufri megha and Rangpuria, were sown under optimal and high-temperature conditions with soil application of inorganic nutrients (N, P, K, Ca, Zn), organic amendment, i.e. farm yard manure (FYM), and straw mulch. This integrative soil management practice showed significant positive influence on membrane integrity, chlorophyll content, total soluble sugars and superoxide dismutase activity of potato plant. Higher tuber bulking rate and tuber yield in both optimal and high-temperature situation was recorded under these soil applications. Kufri megha performed better with the application of Ca and Zn along with straw mulch, while Ca with farm yard manure substantially improved restore yield in Rangpuria. Application of CaSO₄ and ZnSO₄ (20 and 60 kg ha^?1, respectively) with FYM and straw mulch (10 and 6 t ha^?1, respectively) can mitigate the high-temperature stress in potato grown in acidic soil (deficient of Ca and Zn) of northeast India.     

秸秆扩蓄肥对土壤水分和马铃薯产量品质及水分利用的影响

为了增强土壤保水力,改善土壤结构,提高土壤水肥利用效率,该文将玉米、小麦和大豆3种作物秸秆经理化处理并与聚丙烯酰胺(PAM)结合造粒形成的秸秆扩蓄肥应用于马铃薯大田栽培,并与单施钾肥及不施肥处理为对比,研究了3种秸秆扩蓄肥对马铃薯生长发育期间的土壤物理性状、生理特征、产量品质及水分利用效率的影响。结果表明,3种秸秆扩蓄肥具有较强的保水性能,能显著增加0～20cm表层土壤含水率,提高马铃薯苗期、块茎增长期、淀粉累积期的土壤耕层及20～70cm水分;有效降低土壤体积质量,提高非毛管孔隙比例,增加土壤孔隙度;显著提高马铃薯盛花期叶片光合速率、气孔导度和蒸腾速率,增加马铃薯株高、冠幅面积和叶面积。与不施肥处理比较,秸秆扩蓄肥处理的淀粉含量提高12.3%～13.6%,大中薯率提高37.9%～42.8%,产量提高39.3%～50.4%,水分利用效率提高35.6%～45.4%。该研究为秸秆扩蓄肥的推广提供了依据。     

覆盖稻草及加盖薄膜对免耕马铃薯农艺性状及品质的影响

研究了覆盖不同厚度稻草（4、8 cm）以及加盖普通地膜和黑色地膜对免耕马铃薯农艺性状及品质的影响。结果表明：覆盖不同厚度稻草的影响效果具有显著的差异,与覆盖稻草4 cm相比,覆盖稻草8 cm可提高单株结薯数和产量,降低绿薯率,但降低出苗率和株数,其他品质参数差异不明显;在覆盖稻草4 cm的基础上加盖薄膜具有提高单薯重和产量的作用,但在覆盖稻草8 cm的基础上加盖薄膜则对出苗不利,降低了出苗率和株数,降低产量;加盖地膜能显著降低绿薯率,其中黑色地膜的效果优于普通地膜。     

适当保水剂施用和覆盖促进旱作马铃薯生长发育和产量提高

为明确保水剂、秸秆覆盖及行间覆膜等抗旱保水措施对旱作马铃薯渗透调节物质、质膜体系等生理特性的影响和对产量的作用效果,以夏波蒂品种马铃薯为材料,设对照、秸秆覆盖、行间覆膜、单施保水剂、秸秆覆盖加施保水剂、行间覆膜加施保水剂6个处理田间试验。结果表明:各处理的马铃薯叶片细胞质膜透性苗期较大,而后呈先降后升趋势;丙二醛、脯氨酸含量随生育期推进呈逐渐增加趋势;可溶性糖含量呈"单峰"曲线变化。行间覆膜加施保水剂、单施保水剂、秸秆覆盖、秸秆覆盖加施保水剂处理较好地缓和了土壤的干旱情况,有效降低了马铃薯叶片中的渗透调节物质和质膜体系。马铃薯生育后期,至淀粉积累期,各处理脯氨酸含量、可溶性糖含量、质膜透性和丙二醛含量变化较为稳定,行间覆膜加施保水剂处理脯氨酸含量、可溶性糖含量、质膜透性和丙二醛含量较对照分别减少15.57%、6.90%、42.79%和17.69%,单施保水剂处理分别减少2.31%、5.17%、10.62%和8.04%,秸秆覆盖处理分别减少28.45%、3.45%、51.63%和25.58%,秸秆覆盖加施保水剂处理分别减少25.14%、12.07%、49.17%和22.58%,降低干旱胁迫程度明显。马铃薯成熟收获期,秸秆覆盖及其加施保水剂处理各土层的土壤含水率变化相对稳定;0～20cm土层加施保水剂处理的土壤含水率相对高于不加保水剂处理。秸秆覆盖、秸秆覆盖加施保水剂、单施保水剂及行间覆膜加施保水剂处理显著增加了马铃薯产量和商品薯率(P<0.05)。总体上,秸秆覆盖处理较有效地缓和了土壤旱情,秸秆覆盖加施保水剂、单施保水剂和行间覆膜加施保水剂处理作用效果也较好,降低了干旱胁迫程度,促进了马铃薯的生长发育、产量提高。     

深松条件下不同地表覆盖对马铃薯产量及水分利用效率的影响

水分不足是限制旱区作物生长的主要因素,覆盖耕作能够改善土壤的微环境,从而显著提高作物的产量和水分利用效率。为探讨深松结合地表覆盖对土壤物理性状、马铃薯生长、产量及水分利用效率的影响,2013-2015年在宁南旱区采用深松覆盖秸秆、深松覆盖地膜、深松不覆盖3种覆盖耕作模式,以传统耕作不覆盖为对照,对土壤体积质量、团聚体、水分、马铃薯产量和水分利用效率等方面的影响进行了研究。结果表明,与传统耕作相比,深松结合地表覆盖可有效降低耕层土壤体积质量,改善土壤孔隙状况,以深松覆盖秸秆处理效果最佳,深松覆盖秸秆处理0~40 cm平均土壤体积质量较传统耕作降低17.1%。与传统耕作相比,深松覆盖地膜和深松覆盖秸秆处理可使0~40 cm土层0.25 mm机械稳定性团聚体数量显著增加30.7%和17.4%。深松结合不同覆盖方式能有效改善马铃薯生育期0~200 cm土层土壤水分状况,深松覆盖地膜对作物生育前期土壤水分保蓄效果较好,深松覆盖秸秆对生育中后期土壤水分状况的改善效果最佳。深松结合不同覆盖方式下马铃薯植株株高、茎粗及地上部生物量均显著高于传统耕作。作物生育前期以深松覆盖地膜处理效果最佳,中后期以深松覆盖秸秆处理促进作用明显。深松结合地表覆盖能明显提高马铃薯的产量和水分利用效率,深松覆秸秆处理的马铃薯产量、商品薯率和水分利用效率分别较传统耕作处理平均提高37.3%、93.3%和41.2%。通过两年试验研究,在宁南旱区采用深松结合地表覆盖措施具有良好的蓄水保墒效果,对马铃薯生长有利,以深松覆盖秸秆处理的增产和提高水分利用效率效果最为显著。     

Soil temperature and fumigation effects on plant phosphorus uptake and related microbial properties

Early season problems with growth of corn (Zea mays L.) under cool, wet conditions prompted a study of the effects of soil and environmental conditions on mineralization and plant uptake of phosphorus (P). Our objective was to determine the effect of soil test P, temperature, and soil fumigation on soil P availability and uptake during early corn growth. Corn was grown in growth chambers at temperatures of 14°C or 25°C. Soils were a high‐P Hastings silty clay loam (fine, montmorillonitic, mesic Udic Argiustoll) and a low‐P Sharpsburg clay loam (fine, montmorillonitic, mesic Typic Argiudoll). Plants grew for up to 42 d either in soil which had been fumigated with methyl bromide to reduce microbial populations or left unfumigated. We harvested whole pots for soil and plant analysis at 1, 14, 28, and 42 d after planting. Biomass carbon (C) and biomass P were lower in fumigated soils and biomass C increased with time. Fumigation increased Bray Pl‐extractable P at all times. Phosphatase activity and mycorrhizal colonization were both reduced by fumigation. Cumulative plant P uptake was highest in Hastings at 25°C. Higher temperature and higher initial P status increased plant P uptake during early growth. Plants grown in fumigated soil did not take up more P, despite greater extractable P.     

Decreases in microbial functional diversity do not result in corresponding changes in decomposition under different moisture conditions

This study compares the functional capability of soils with differing microbial diversity. Soil microbial diversity was modified by either fumigation with reinoculation by unfumigated soil or fumigation with no reinoculation. Functional capability was assessed by following wheat straw decomposition in these soils and in an unfumigated control soil at three matric potentials (−5, −125 and −800 kPa). The changes in diversity after fumigation were compared with the effects of disturbance treatments (slow air-drying, rapid oven-drying, 2 mm sieving and 0.5 mm sieving) by studying patterns of in situ catabolic potential (ISCP) at 1 and 8 weeks. Five weeks after the fumigation treatments, the functional and phenotypic diversity of the soil microbial community, as revealed by patterns of ISCP and phospholipid fatty acid (PLFA) profiles, respectively, were greatly different from that in unfumigated soil. The effects of the fumigation reinoculation treatment on functional diversity were comparable with those caused by rapid oven-drying, but were greater than the effects of 0.5 mm sieving. These disturbance treatments caused persistent changes in functional diversity, whereas slow air-drying and 2 mm sieving had little influence on diversity. Rates of straw decomposition were initially greater in the fumigated reinoculated soil than in the unfumigated soil at all moisture potentials. In contrast, straw mineralisation rates in the fumigated uninoculated soil generally exceeded rates in unfumigated soil for a period after 14 d, which was shorter at greater moisture potentials. These rates resulted in total straw mineralisation in fumigated reinoculated soil exceeding that in unfumigated soil at all moisture potentials. Compared with the unfumigated soils, total straw mineralisation in fumigated uninoculated soil was less at −5 kPa, similar at −125 kPa and greater at −800 kPa. The results indicated that the decomposition function of soil with reduced functional diversity can be diminished under optimum moisture conditions, but is not invariably reduced when assessed under suboptimal moisture conditions. This indicated that decreases in the functional diversity of soil microbial communities may not consistently result in declines in soil functioning.     

Yield and Quality of Leek in Response to Compost Applied as a Mulch or Incorporated Into the Soil

Compost is widely used to increase soil fertility, usually practiced by incorporating the compost into the upper soil layer. This study questions the rationale behind this practice. Compost was applied as a mulch and compared with compost worked into the soil in a growth experiment with leek (Allium porrum L. Var. ‘Siegfried Frost’). The compost used was made of source separated organic waste from either gardens and parks, or households. Garden-park compost was applied in 2.5 times greater volumes than household compost to compensate for its lower content of nutrients. The soil was either sandy loam or clay loam. Each of the eight combinations of variables (application method, compost type, and soil type) was repeated three times with 20 leeks in each replicate. Significantly higher yields were obtained with compost applied as a mulch. Here, the yield averaged 78 g fresh weight per leek, compared to 59 g per leek from plots with compost incorporated. Compost mulching also resulted in a significantly higher quality leeks, including more first class leeks, longer and thicker shafts, and a generally better appearance. The advantage of placing the compost on the soil surface rather than thoroughly mixing it with the soil can be attributed to a higher availability of plant nutrients. No significant effect of compost type on leek yield was observed, indicating that the 2.5 times higher volumetric dose of garden-park compost provided the same amount of available nutrients as a single dose of household compost. The soil type did not significantly influence the yields either, which is attributable to both soils being well structured prior to compost amendment.     

Nutrient uptake and growth of potato: Arbuscular mycorrhiza symbiosis interacts with quality and quantity of amended biochars

Aims : The aim of this study was to explore interactive effects between quality (types) and quantity (application rates) of biochar as well as of arbuscular mycorrhiza (AM) symbiosis on the growth of potato plants. Methods : A low P sandy loam soil was amended with 0%, 1.5%, or 2.5% (w/w) of either of 4 types of biochar, which were produced from wheat straw pellets (WSP) or miscanthus straw pellets (MSP) pyrolyzed at temperatures of either 550°C or 700°C. Potato plants grown in pots containing the soils or soil biochar mixture were inoculated with or without AM fungus (AMF), Rhizophagus irregularis. The experiment was carried out under fully irrigated semi‐field conditions and plants were harvested 101 days after planting. Results : Application of high temperature biochar decreased growth, biomass and tuber yield of potato plants, while the low temperature biochar had a similar effect on yield as plants grown without biochar amendment. Total biomass of potato plants were decreased with the increasing rate of biochar. Arbuscular mycorrhizal fungus inoculation stimulated the growth of potato plants in all organs, increased tuber biomass significantly in 1.5% MSP700 amended plants, and to a lesser degree for WSP700, MSP550, and WSP550. In addition, plant biomass gain was linearly related to N, P, and K uptake, the ratio of P to N in the leaf of plants indicated that all treatments were mainly P‐limited. A multiple linear regression using P uptake and biochar rate as independent variables explained 91% of the variation in total biomass. The single effect of AMF inoculation, type and rate of biochar affected plant N, P and K uptake similarly. While AMF inoculation significantly increased P uptake in potato plants grown in soil with WSP700 or MSP700 despite of the rate of biochar. In general, application of biochar significantly increased AMF root colonization of potato plants. Conclusions : The application of MSP550 at 1.5% combined with AMF stimulated growth of potato the most. Furthermore, the results indicated that the interactive effect of AMF inoculation, biochar type and application rate on potato growth to a large extent could be explained by effects on plant nutrient uptake.     

Rice yield nutrient uptake as affected by cyanobacteria soil amendments—a pot experiment

Rice production and cyanobacterial N in acid soil can be improved by liming. There is evidence that the organic amendments can increase the soil pH. The aim of this study was to find appropriate combination of soil amendments and cyanobacteria capable for enhancing nutrient uptake and improving rice yield in acidic paddy soil. Three soil amendments (rice straw, sewage‐sludge composts, NPK) with and without inoculation of cyanobacteria were studied for rice plants (Oryza sativa L.) in a pot experiment. The sludge compost had significantly reduced soil acidity from 5.44 to 6.67. The plant N and K uptake increased significantly with sludge and cyanobacteria application. The yield components increased significantly with sludge, but decreased thereafter, an exception was the number of panicles, with straw compost. These characters were also significantly affected by inoculation with cyanobacteria except 100‐grain weight, filled‐grain percentage, and harvest index. The combination of sludge compost and cyanobacteria improved the yield components and consequently grain yield (138 g pot^–1) compared with sludge treatment only (132 g pot^–1). The amount of cyanobacterial N absorbed (N‐difference method) by rice plant under sludge compost was higher than that of soils amended with either rice straw or NPK treatments. Therefore, the addition of sewage sludge to acid paddy soil not only amended the soil properties but also activated the cyanobacteria and consequently improved rice plant nutrition and grain yield.     

Colored plastic mulches affect soil temperature and tuber production of potato

Abstract

The main crops on which plastic mulch is widely used in Mexico include tomato, bell pepper, eggplant, melons, watermelons, and strawberry; however, very little research has been performed on potato. One of the main benefits associated with plastic mulching is the modification of the microclimate around the plant. To obtain a positive microclimate modification studies are required to understand how plastic mulch affects growth and yield of a given species. Previous field research assessing the response to colored plastic mulching in potato shows no consistent results on yield, maybe because it has been performed under different geographical latitudes. Potato in Mexico is conventionally cultivated on bare soil combined with various irrigation systems. The objective of the present study was to examine the effect of colored plastic mulches on soil temperature, growth, yield and photosynthetic response of potato plants. The experiment was conducted in Northeast Mexico and the treatments included were: black plastic mulch (BPM); white-on-black plastic mulch (W/B), silver-on-black (SPM), aluminum-on-black plastic mulch (APM) and a control that consisted of bare soil cultivated plants. Treatments were arranged in a randomized complete block design with four replications. Results suggest that average daily mean soil temperature was linearly and negatively correlated with total yield and yield of first-quality tubers. Total yield and yield of first-quality tubers of plants mulched with W/B, SPM and APM was significantly higher (p≤0.05) than those of control plants. Leaf area and shoot dry weight were increased when soil temperatures were higher due to the effect of radiation transmission to the soil, however, this decrease was associated with a decrease in tuber production. The results of our study indicate that plants grown under BPM, which induced the highest soil temperature, showed marginal difference in yield compared with control plants, suggesting that colored plastic mulches have a positive effect on yield through decreased rise in soil temperature.     

Soil microbial, fungal, and nematode responses to soil fumigation and cover crops under potato production

Sodium N-methyldithiocarbamate (metam sodium) and 1,3 dichloropropene are widely used in potato production for the control of soil-borne pathogens, weeds, and plant parasitic nematodes that reduce crop yield and quality. Soil fumigation with metam sodium has been shown in microcosm studies to significantly reduce soil microbial populations and important soil processes such as C and N mineralization. However, few published data report the impact of metam sodium on microbial populations and activities in potato production systems under field conditions. Fall-planted white mustard (Brassica hirta) and sudangrass (Sorghum sudanense) cover crops may serve as an alternative to soil fumigation. The effect of metam sodium and cover crops was determined on soil microbial populations, soil-borne pathogens (Verticillium dahliae, Pythium spp., and Fusarium spp.), free-living and plant-parasitic nematodes, and C and N mineralization potentials under potato production on five soil types in the Columbia Basin of Eastern Washington. Microbial biomass C was 8–23% greater in cover crop treatments compared to those fumigated with metam sodium among the soil types tested. Replacing fumigation with cover crops did not significantly affect C or N mineralization potentials. Cumulative N mineralized over a 49-day laboratory incubation averaged 18 mg NO₃-N kg⁻¹ soil across all soil types and treatments. There was a general trend for N mineralized from fumigated treatments to be lower than cover-cropped treatments. Soil fungal populations and free-living nematode levels were significantly lowered in fumigated field trials compared to cover-cropped treatments. Fumigation among the five soil types significantly reduced Pythium spp. by 97%, Fusarium spp. by 84%, and V. dahliae by 56% compared to the mustard cover crop treatment. The percentage of bacteria and fungi surviving fumigation was greater for fine- than coarse-textured soils, suggesting physical protection of organisms within the soil matrix or a reduced penetration and distribution of the fumigants. This suggests the potential need for a higher rate of fumigant to be used in fine-textured soils to obtain comparable reductions in soil-borne pathogens.     

Limitations in the application of the fumigation technique for biomass estimations in amended soils

The fumigation technique for the estimation of microbial biomass-C was applied at different periods after amendment of three agricultural soils with ¹⁴C-labelled glucose, cellulose and wheat roots. By daily monitoring of evolved CO₂ and ¹⁴CO₂ it was recognized that the CO₂ from the degradation of the amendment had an interfering effect on biomass calculations. Biomass estimations were valid only when CO₂ from the degradation of the amendment had slowed, 3 days after glucose amendment, 14 days after addition of cellulose, and 28 days after amendment with wheat roots.Fumigated, reinoculated soils degraded glucose faster than did the corresponding control samples, causing an overestimation of biomass-C. By contrast biomass-C was underestimated in soils amended with cellulose or wheat roots due to lower rates of degradation of the added C-sources in fumigated samples. The reduced capacity for degradation of complex organic materials may be due to smaller decomposer populations in inoculated fumigated soils; populations recovered within 20 days to only 10–20% of their original biomass-C content. Re-establishment of biomass in fumigated samples was tested with inocula in amounts increasing to 10, 50 and 100% of corresponding control samples. The K-factor was not influenced by these treatments. Estimates of biomass in soil during the rapid phase of degradation of wheat roots were influenced by the amount of inoculum.     

The influence of compost and zeolite co‐addition on the nutrients status and plant growth in intensively cultivated Mediterranean soils

The main objective of the study was to test the benefits of compost and zeolite co‐addition on the fertility of organic‐rich Mediterranean soils. Previous pot study in greenhouse found that zeolites mixed with compost significantly improved potassium availability as well as exchangeable potassium capacity in the soils. To further test this finding, a field experiment was conducted using potato – Solanum tuberosum L., desiree cultivar in peat soils of the Hula Valley, Israel. Adhering to the protocol of the greenhouse experiments, the treatments included 5% compost addition with no zeolites, 2% zeolite addition without compost, co‐addition of 5% compost mixed with 2% zeolites and control. We found that compost addition increased significantly the potatoes yield and the number of large tubers; however, the zeolite addition had no impact on yield. Co‐addition of compost and zeolites did not improve total crop yield or number of large tubers compared with compost addition only. The results are consistent with nutrients availability (N, P, K) across the treatments. In a commercialized field using the experiment conditions, the 2% zeolite addition would amount to 18 ton of zeolites per hectare. Hence, we conclude that soil amendment with the tested zeolite might be beneficial to improve soil retention for cationic nutrients (e.g. K⁺) under high leaching systems such as plant culture in pots, but in the field with high loads of compost, its effect is minor.     

Decomposition of carbon-14-labelled wheat straw in repeatedly fumigated and non-fumigated soils with different levels of heavy metal contamination

We analysed the decomposition of ¹⁴C-labelled straw at five different levels of heavy metal contamination (100-20,000 µg total Zn g^-1 soil) in non-fumigated and repeatedly fumigated soils. The soils were not spiked with Zn, but were taken from sites containing different heavy metal concentrations. Zn was only used as a reference and the effects observed are most likely due to this metal. Microbial biomass decreased with increasing heavy metal content of soils, paralleled generally by the decreasing amount of wheat straw ¹⁴C incorporated into the microbial biomass. In addition, the newly synthesised microbial biomass declined more rapidly as the incubation proceeded. In the repeatedly fumigated soils, microbial biomass ¹⁴C corresponded to roughly 50% of the maximum ¹⁴C incorporation of the non-fumigated soil. The relative decline during incubation was similar to that of the non-fumigated soil at the respective contamination level. These results reveal clearly that heavy metal effects on straw decomposition do not depend on the ratio of substrate C to microbial biomass C. In contrast to microbial biomass C, the mineralisation of the wheat straw was not seriously affected by heavy metal contamination. The same was true for all of the repeatedly fumigated treatments, where a much smaller microbial biomass mineralised nearly the same amount of straw as in the non-fumigated soils. However, repeated fumigation caused a strong reduction in the decomposition of soil organic matter. The ratio of CO₂-¹⁴C to microbial biomass ¹⁴C after 60 days was linearly related to the Zn concentration in both non-fumigated and repeatedly fumigated samples, clearly indicating that an additional energy cost is required by soil microorganisms with increasing heavy metal concentrations.     

覆盖方式对旱地马铃薯阶段耗水量特征和产量的影响

为明确不同覆盖方式对旱地马铃薯田土壤耗水、耗水规律、水分利用效率、产量及产量形成的影响,在陇中半干旱农区设置了玉米秸秆带状双行覆盖(SSM2)、玉米秸秆带状单行覆盖(SSM1)、玉米秸秆全覆盖(SFM)、地膜春覆盖(PMS)和地膜秋覆盖(PMA)5种覆盖方式,以传统露地平作为对照(CK)。结果表明:2年试验中,玉米秸秆带状覆盖和地膜覆盖处理土壤贮水消耗量较CK分别增加13.5,14.8 mm。玉米秸秆带状覆盖能显著提高降水对马铃薯耗水贡献率,不同降雨年型内均以SSM2处理贡献率最高,2年分别为95.6%和94.3%。于CK相比,覆盖处理均降低了生育前期(播种-块茎形成期)耗水量,地膜覆盖显著增加了生育中期(块茎形成期-淀粉积累期)耗水量,玉米秸秆带状覆盖显著增加了生育后期(淀粉积累期-收获期)的耗水量。玉米秸秆带状覆盖和地膜覆盖分别能使马铃薯干薯产量增加27.9%和24.2%,干薯水分利用效率提高23.1%和19.3%。综上可知,玉米秸秆带状覆盖处理能显著增加马铃薯生育时期内农田土壤贮水消耗量,并改善马铃薯生育前期和生育后期耗水,减少旱地马铃薯农田无效耗水,能显著提高马铃薯干薯产量和水分利用效率。     

水氮耦合对膜下滴灌马铃薯产量、品质及水分利用的影响

该文通过田间试验,研究在西北旱区对膜下滴灌条件下水氮耦合效应及其对马铃薯产量、品质和水分利用效率的影响,从而确定马铃薯适宜的水氮用量,以求达到节水、节肥和高产优质的目的。试验设置2个土壤湿润比水平:40%(P1)和70%(P2),5个施氮水平:90(N1)、135(N2)、180(N3)、225(N4)、270kg/hm2(N5),共10个处理。试验结果表明:相同水分条件下,马铃薯块茎质量、块茎淀粉含量、块茎维生素C含量、耗水量、产量和水分利用效率都随施氮量的增加而呈抛物线趋势变化,块茎蛋白质含量随施氮量的增加呈增加趋势。相同氮肥条件下,湿润比P2处理的马铃薯块茎质量、块茎淀粉含量、块茎维生素C含量、块茎蛋白质含量均高于湿润比P1,湿润比P2处理的耗水量比湿润比处理P1高11%,湿润比P2处理的产量比湿润比处理P1高5%,但是湿润比P1处理的水分利用效率比湿润比P2处理高5.4%。其中,P2N3处理的马铃薯单株块茎质量、块茎维生素C含量表现最好,P1N5处理的马铃薯块茎蛋白质含量最高,P2N2处理的马铃薯块茎淀粉含量和产量表现最优,产量最高为54187kg/hm2,P1N2处理的水分利用效率最高为12.86kg/m3。P2N3处理的马铃薯高产优质,且水分利用效率较高,是西北旱区膜下滴灌条件下马铃薯生产中适宜的水氮组合。     

Influence of mulch C/N ratio and decomposition stage on plant N uptake and N availability in soil with or without wheat straw

Mulches can improve soil properties, but little is known about nutrient availability in mulched soil that contains plant residues and the effect of mulching with manures. The aim of this study was to determine the effects of mulching with high or low C/N organic materials, in which low C/N materials differed in decomposability, and the presence of wheat straw in the soil on plant growth and N uptake, soil N availability and microbial biomass N within about four months after mulching. Three organic materials were used: mature wheat straw (W, C/N 80), young faba bean shoots (FB, C/N 7), and sheep manure (SM, C/N 8). There were eight treatments differing in amendment methods (mulching or mixing with W or both) and mulching materials (W, FB or SM). Treatments that were only mulched with W, FB or SM are referred to as m‐treatments. In m/s‐treatments, after W was mixed into the soil, W, FB or SM were placed on the soil surface as mulch. Two other treatments included an unamended control and soil mixed with W. Wheat was planted 0, 35 or 70 days after mulching (referred to as 0, 35, and 70 DAM) and grown for 35 days. Faba bean mulch increased shoot dry weight, shoot N uptake and available N compared to wheat or sheep manure mulch, particularly in the m‐treatments. Shoot dry weight was higher in m‐treatments than corresponding m/s‐treatments with the same mulch type. Shoot N uptake was higher in 70 DAM than in 0 DAM in all treatments and 0.3 to three‐fold higher in m‐treatments than the corresponding m/s‐treatments. Microbial biomass N was higher in 0 DAM than in 35 and 70 DAM in most treatments and up to two‐fold higher in m/s‐treatments than the corresponding m‐treatments. Available N in m/s‐treatments was two to six‐fold higher than m‐treatments in 0 DAM, but differed little in older mulch ages of W and SM. It can be concluded that compared to soil with only mulch, mixing of wheat straw into soil reduced plant growth and N uptake, particularly in the early stages of mulching (0 and 35 DAM). However, the presence of wheat in mulched soil may provide a longer lasting source of N for plants and reduce the risk of N leaching from rapidly decomposing low C/N mulch due to greater microbial biomass N uptake than only soil with mulch.     

补充灌溉、氮素营养与秸秆覆盖对冬小麦生长及产量的影响研究

大田试验研究补充灌水、施N肥与秸秆覆盖对冬小麦根系和地上部生长、产量及其构成因子的影响结果表明 ,施N肥对冬小麦生长发育和产量的效应最明显 ,单独覆盖秸秆或补充灌水基本无效甚至出现副作用。施用N肥和秸秆覆盖可促进冬小麦根系发育和地上部生物量累积。肥料供应充足时覆盖秸秆对冬小麦根系的作用与水分状况有关 ,土壤水分胁迫下秸秆覆盖效果不明显 ,此时施用N肥甚至出现一定负效应。水分充足与否 ,施N肥和秸秆覆盖均对冬小麦产量的形成有一定协同效应 ,补充灌溉与施用N肥和秸秆覆盖配合处理小麦产量最高。     

Influence of phytoparasitic nematodes on symbiotic N2 fixation in tropical herbaceous legume cover crops

 Populations of plant parasitic nematodes and their effects on symbiotic nitrogen (N) fixation in herbaceous legumes and on some selected characteristics of other plant species associated with such cover crops were studied. Two legume species [mucuna, Mucuna pruriens (L) DC. var. utilis (Wright) Bruck and lablab, Lablab purpureus L. Sweet], one grass/weed species [imperata, Imperata cylindrica (L.) Rauschel] and a cereal (maize, Zea mays L.) were used. There were three soil treatments (fumigation, fumigation plus inoculation with Meloidogyne species, and an untreated control). Plant parasitic nematode populations in soil, roots and nodules were determined at 4, 8 and 12 weeks after planting. The response of the phytoparasitic nematodes to soil treatments varied according to the plant species present. The predominant nematodes in soils, roots and nodules of legumes were of the genus Meloidogyne, whereas other genera of parasitic nematodes dominated the fauna in soils and roots of maize and imperata. Biomass yield of mucuna was not significantly affected by either Meloidogyne spp. or the other genera of phytoparasitic nematodes. In contrast, the dry matter yield of lablab measured at 12 weeks was reduced by 16% in inoculated compared with fumigated soils. Similarly, the biomass yields of maize and imperata were reduced by 10% and 29%, respectively, in unfumigated rather than fumigated soils. The amounts of N accumulated in mucuna, maize and imperata were not significantly affected by the two groups of plant parasitic nematodes. However, at 12 weeks, lablab grown on inoculated soils accumulated only 69% of the N found in plants grown on fumigated soils. Inoculation of soil with Meloidogyne spp. significantly increased the number of nodules on lablab roots compared with the non-inoculated treatments, whereas nodulation in mucuna was not affected by soil treatment. After 12 weeks, the quantity of N₂ derived from symbiotic fixation in mucuna was not significantly affected by soil treatments whereas the amount of fixed N in lablab was 32% lower in inoculated than in fumigated soils. Possible mechanisms for the non-suppressive effect of plant parasitic nematodes on mucuna are discussed. Received: 12 March 1999