Soil nutrient loss due to tuber crop harvesting and its environmental impact in the North China Plain

Soil loss due to crop harvesting （SLCH） is a soil erosion process that signiifcantly contributes to soil degradation in crop-lands. However, little is known about soil nutrient losses caused by SLCH and its environmental impacts. In the North China Plain area, we measured the losses of soil organic carbon （SOC） and nitrogen as wel as phosphorus due to SLCH and assessed their relationship with soil particle size composition, agronomic practices and soil moisture content. Our results show that the losses by harvesting potato of SOC, total nitrogen （TN）, available nitrogen （AN）, available phosphorus （AP） and total phosphorus （TP） were 1.7, 1.8, 1.8, 15.9 and 14.1 times compared by harvesting sweet potato, respectively. The variation of SOC, N and P loss by SLCH are mainly explained by the variation of plant density （PD） （17–50%）, net mass of an individual tuber （Mcrop/p） （16–74%）, soil clay content （34–70%） and water content （19–46%）. Taking into account the current sewage treatment system and the ratio of the nutrients adhering to the tubers during transportation from the ifeld （NTRP/SP）, the loss of TN and TP by harvesting of potato and sweet potato in the North China Plain area amounts to 3% N and 20% P loads in the water bodies of this region. The fate of the exported N and P in the sewage treatment system ultimately controls the contribution of N and P to the polution of lakes and rivers. Our results suggest that a large amount of SLCH-induced soil nutrient export during transportation from the ifeld is a potential polutant source for agricultural water for vast planting areas of tuber crops in China, and should not be overlooked.

Impact of Tree Stump Harvesting on Soil Carbon and Nutrients and Second Rotation Tree Growth in Mid-Wales, UK

The drive to develop renewable energy is increasing the interest in energy forestry. Woody biomass from forest residues has the potential to make a significant contribution to greenhouse gas emission reduction through fossil fuel substitution. However, there is a danger of operational practice running ahead of the understanding of the environmental impacts of such activities. Consequently, there is an urgent requirement for scientifically underpinned guidance on the best management practices to ensure soil and water protection, including sustaining forestry’s key role in carbon capture. This study addresses the main issues associated with stump harvesting practices and their impacts on soil carbon and nutrient capital and effects on the second rotation tree growth. It reports results from a clearfell site in the UK where experimental stump harvesting was carried out in 2005 before replanting with Sitka spruce Picea sitchensis (Bon.)Carr. Both stump harvested and conventional harvested areas (Control) were studied in 2009 and 2010, five years after harvesting, on the two distinct soil types at the site: podzolised brown earth and peaty gley soils. Results show impacts of stump harvesting on soil carbon and nitrogen stocks, residual water, base cations (K+, Ca2+ and Mg2+) concentrations and stocks and bulk density in both soil types. The organic peaty gley soil showed larger and deeper profile changes after stump harvesting compared with the podzolised brown mineral soil, where some of the negative changes in C, N and base cations in the top soil were compensated by increases at depth. Tree assessment showed positive effect of stump harvesting on K and Ca uptake by young seedlings, but N and P nutrient status was reduced on the peaty gley soils. The overall results support the current UK forestry guidance for stump harvesting which identifies that soil type is the most important site factor determining the sustainability of the practice.

Eucalyptus grandis plantations:effects of management on soil carbon,nutrient contents and yields

The expansion of fast-growing tree plantations is a worldwide process,with consequences on soil fertility and soil carbon storage.Disparate results were found on the effects of afforestation with Eucalyptus on soil carbon and other nutrient contents.These discrepancies are usually caused by differences in climate,land use history,soil texture as well as by management related factors such as plantation age,number of rotations,method of establishment(plantation or coppice),harvest residue management and soil preparation.We studied the effect of plantation age,number of rotations,and method of establishment on soils and plant nutrient concentrations in Eucalyptus grandis plantations in NE Argentina on different textured soils.We also determined if yields changed with nutrient variations in soils,and compared soils under plantations to soils under grasslands they replaced.Thirty-one E.grandis stands of different ages,number of rotations and method of establishment were evaluated as well as eight grassland sites.Levels of carbon,nitrogen,phosphorus,potassium,calcium and magnesium were determined for soils and plants.Soil carbon and nitrogen decreased over the number of rotations and were more pronounced in soils with 50-60%sand than soils with>75%sand.Coppice stands showed higher soil carbon and nitrogen levels than plantations,suggesting a negative effect of site preparation before planting on soil nutrient conservation,especially in fine-textured soils.Foliar nutrient concentrations did not follow the trends observed for soil nutrients nor did they reflect nutrient limitations.There was no evidence of decreased yields over successive rotations.Soil carbon and nitrogen contents decrease when grasslands are replaced by E.grandis plantations,and therefore a yield limitation may occur in a medium to long-term frame,especially in stands re-established for short-rotation management.Harvest residue management and site preparation must be specifically designed for improving soil nutrient management.

内蒙古半干旱冷凉地区燕麦与箭筈豌豆混播生产性能及营养价值评价

为筛选出适宜内蒙古半干旱冷凉地区燕麦(Avena sativa)与箭筈豌豆(Vicia sativa)最佳混播组合、比例和刈割期,本研究以燕麦‘蒙饲燕1号’(‘Mengsiyan 1’)、‘蒙饲燕2号’(‘Mengsiyan 2’)、‘青引1号’(‘Qing yin1’)分别和箭筈豌豆混播为研究对象,对不同混播组合和比例的饲草在不同刈割期生产性能、营养品质及土壤养分等指标进行测定分析与综合评价。结果表明:1)不同混播能够显著提高箭筈豌豆的株高、鲜重和干重(P <0.05);以燕麦150 kg·hm^(−2)和箭筈豌豆75 kg·hm^(−2)单播量配比的‘蒙饲燕1号’+箭筈豌豆混播(3:1)在乳熟期、‘蒙饲燕2号’+箭筈豌豆混播(1:1)在乳熟末期干草产量最高;‘青引1号’+箭筈豌豆混播在各刈割期干草产量均低于同期燕麦单播产量。2)不同混播处理粗蛋白含量较燕麦单播基本呈增加趋势,粗蛋白含量从抽穗期、乳熟期到乳熟末期逐渐降低;水溶性碳水化合物(WSC)含量均在乳熟末期达到最高;不同混播组合在1:3的比例下酸性洗涤纤维(ADF)和中性洗涤纤维(NDF)含量均最低。3)燕麦与箭筈豌豆混播能够显著提高土壤有机质和速效氮含量。通过隶属函数法对混播饲草产量与营养品质进行综合评价,各混播组合中‘蒙饲燕1号’+箭筈豌豆混播(1:3)、‘蒙饲燕2号’+箭筈豌豆混播(1:1)和‘青引1号’+箭筈豌豆混播(1:3)分别在乳熟末期刈割隶属综合评价值较高,其中‘蒙饲燕1号’+箭筈豌豆混播(1:3)最佳(0.70)。

施肥和收获期对拉萨河谷地区白草产量和饲用品质的影响

为探究西藏地区白草(Pennisetum flaccidum)优质、高产的种植方式,本研究在拉萨河谷区设置N_(0)(0 kg·hm^(-2))、N_(300)(300 kg·hm^(-2))、N_(600)(600 kg·hm^(-2))和N_(900)(900 kg·hm^(-2))施肥处理,分别于抽穗期、乳熟期和成熟期采集试验样品,分析不同施肥梯度和收获期对白草产量、饲用品质和土壤养分的影响。结果表明:白草干草产量随施肥量增加呈上升趋势,在抽穗期和成熟期显著高于乳熟期(P<0.05)。白草粗蛋白含量随收获期推迟而逐渐降低,粗灰分含量随施肥量增加呈下降趋势,但施肥对不同收获期的白草酸性洗涤纤维、中性洗涤纤维、粗脂肪和酸性洗涤木质素含量均无显著影响(P>0.05)。白草土壤全氮含量在抽穗期随施肥量增加呈现先增后减趋势,全磷含量随施肥量增加以及收获期的推迟而趋于下降。在抽穗期收割N_(900)处理的白草生产性能最佳,其次是同期收割N_(600)处理的白草,但后者较前者拥有更优的经济和生态效益。

Impact of trimming intensity on the growth of mangrove in Iran

Mangrove forests in southern Iran are of high ecological and economic importance.These forests are being threatened because of uncontrolled harvesting to provide fodder for livestock.The objective of this study is to provide recommendations for appropriate harvesting intensities by quantifying the effect of different harvesting intensities on vegetative and vigor characteristics of mangrove trees.This study was conducted using a randomized complete block design comprising four treatments(10.00%,20.00%,and 30.00% trimming,along with a control)replicated three times.Vegetative characteristics were measured before and after trimming(five-year period)and analyzed using generalized linear model statistical analysis.The growths of the average diameter of canopy,canopy area,canopy volume,canopy height,tree height,and collar diameter in the control treatment were all significantly higher than those in the trimming treatments.In addition,there was a decreasing trend in leaf fresh and dry mass,leaf area index,total area of canopy leaves,and health status of tree in the trimming treatments.For example,the percentage change in fresh and dry leaf mass in the control treatment was positive(29.87% and 38.31%,respectively),whereas the trimming treatments of 10.00%,20.00% and 30.00% had negative effects(-7.01% and -4.79%,-11.32% and -14.30%,and -15.84% and -17.29%,respectively).In addition,the changes in leaf area index in the control(4.95%)and 30.00% trimming(-24.57%)treatments were the highest and lowest,respectively.The percentage change in soil organic matter in the control,10.00%,20.00%,and 30.00% treatments were 22.94%,-9.90%,-16.91%,and -18.68%,respectively.The study demonstrated that gray mangrove trees were highly sensitive to canopy trimming,with even minimal trimming intensities negatively affecting vegetative growth and soil organic matter.Therefore,it is recommended that cutting and trimming of mangrove trees should be prevented even at low intensity to preserve mangrove ecosystem health and resilience against environmental stressors.

生物炭类型和施用量对陕北黄绵土土壤理化性状和谷子生长的影响

【目的】探明不同生物炭类型和施用量对陕北黄绵土理化性状和谷子生长的影响。【方法】选取玉米秸秆(JG)、稻壳(DK)和竹竿(ZG)3种生物炭,分别设置C1(300 g/m^(2))、C2(600 g/m^(2))、C3(1200 g/m^(2))3个施炭水平,以不施生物炭为对照(CK),开展谷子室内模拟栽培试验,通过测定土壤理化指标和谷子生长指标,探究不同生物炭类型和施用量对陕北黄绵土土壤理化性状及谷子生长的影响。【结果】DK生物炭对土壤含水量和容重有显著的调控作用,DKC2处理的土壤含水量较JGC2和ZGC2处理分别显著下降15.78%、18.26%(P<0.05);DKC3处理的土壤容重较JGC3和ZGC3分别显著下降20.07%、24.63%(P<0.05);施ZG生物炭时,土壤有机碳、速效钾含量随生物炭施用量增加逐渐递增,ZGC3处理下,土壤有机碳、速效钾含量较CK分别显著提升134.35%、77.94%(P<0.05)。施JG生物炭时,谷子株高、地上部干重随生物炭施用量的增加先增后减,且JGC2处理下谷子株高、地上部干重较CK分别显著提升32.62%、77.13%(P<0.05),单穗粒重、总干重及小区产量较施DKC2、ZGC2处理分别显著提升126.18%、65.36%、57.54%和79.25%、82.46%%、50.37%(P<0.05)。施DK生物炭的谷子地下部干重、根表面积和根冠比随生物炭施用量的增加先增后减,DKC2处理谷子地下部干重、根表面积和根冠比较CK分别显著提升104.53%、90.30%、82.11%(P<0.05);ZGC3处理谷子收获指数较施DKC3显著提升50.00%(P<0.05)。【结论】不同生物炭类型及施用量对谷子的生长影响各异,600 g/m^(2)玉米秸秆生物炭处理更利于谷子干重的提升、600 g/m^(2)稻壳生物炭处理更利于谷子根系的生长、1200 g/m^(2)竹竿处理更利于谷子收获指数的提升。在陕北黄绵土中种植谷子,施玉米秸秆、竹竿生物炭具有较好的土壤水肥调节能力和增产增效作用。

垄覆黑膜沟覆秸秆促进夏玉米生长及养分吸收

针对中国西北干旱半干旱地区降水年际变率大、年内分配不均衡的气候特点,探究更为有效的农田集雨模式以实现农业的稳产高效和可持续发展。通过2 a田间试验,对比研究了不覆盖(CK)、垄覆白膜沟不覆盖(M1)、垄不覆盖沟覆秸秆(M2)、垄覆白膜沟覆秸秆(M3)和垄覆黑膜沟覆秸秆(M4)5种集雨模式对夏玉米生长、养分吸收利用及土壤有机质含量和硝态氮分布的影响。结果表明,夏玉米地上部生物量随生育进程的动态变化符合Logistic生长模型。处理M4地上部生物量理论最大值最高,快速生长持续时间最长,根系最发达;夏玉米根系主要分布在0~40 cm土层,且覆盖条件下,根长分布呈浅根化趋势。覆盖秸秆可有效提高土壤有机质含量;不同集雨模式下土壤硝态氮峰值所在土层深度存在差异,其中处理M3和M4硝态氮入渗较深,但其峰值仍保持在200 cm土层内,不会产生深层渗漏。夏玉米各器官中养分累积量表现为果>叶>茎>根(其中K素累积量为茎略大于叶)。2 a中各覆盖处理夏玉米植株氮、磷和钾吸收效率及肥料偏生产力均显著(P<0.05)高于对照。其中处理M4的平均肥料偏生产力分别较处理M1、M2和M3提高8.37%、14.93%和3.74%。综合分析,全程微型聚水覆盖(M3和M4)尤其是垄覆黑膜沟覆秸秆可较好的促进植株生长及养分吸收,同时能维持地力,具有较大的增效潜力。该研究可为干旱半干旱地区改善集雨种植模式、提高农业生产力提供参考。

垄覆膜集雨种植对二年龄苜蓿草地土壤养分的影响

旱作条件下,垄覆膜集雨措施应用于紫花苜蓿种植,垄为集雨区,沟为种植区,研究不同沟垄宽比和覆膜方式对2年龄苜蓿草地土壤养分影响。结果表明,垄覆膜种植苜蓿第2年返青前、第2茬刈割后,各处理0～20,20～40cm土壤全磷(TP)含量均无显著差异,膜垄、土垄处理0～20,20～40cm土壤有机质(SOM)、全氮(TN)含量均随着垄宽度的增大而增加,且膜垄处理0～40cm土层SOM、TN、速效氮(AN)、速效磷(AP)、缓效钾(SAK)、速效钾(AK)含量均显著高于土垄处理及CK(平作),所有处理中MR60、MR75土壤养分含量最高。刈割后和返青前相比,膜垄处理0～40cm土层SOM的减少量显著低于土垄处理,膜垄处理0～40cm土层TN的增加量及AN、AP、SAK、AK的减少量均显著大于土垄处理;相关性分析表明,各处理0～40cm土层SOM的减少量与苜蓿的经济产量呈显著的负相关,0～40cm土层TN的增加量、AP的减少量、AK的减少量均与苜蓿的经济产量呈显著的正相关。说明垄覆膜集雨种植紫花苜蓿能够有效的抑制SOM含量的降低,且膜垄的抑制作用大于土垄,同时促进TN含量的增加,有效地提高0～40cm土壤养分,有利于土壤的可持续利用。

采伐干扰对巨桉人工林土壤养分和酶活性的影响

研究了巨桉二代萌生林土壤水热条件、养分状况和酶活性。结果表明,与巨桉人工林比较,采伐后的巨桉二代萌生林地E1和E2的土壤含水量增加,0～20cm土壤温度升高,土壤有机质、碱解N、蔗糖酶、脲酶、磷酸酶和过氧化氢酶活性均提高,但有效P含量减少,pH值减低,土壤酸性增强。保留采伐剩余物的样地E1,其土壤含水量、有机质、水解N、有效P和蔗糖酶含量高于E2,分别高12.77%、25.27%、11.82%、6.25%和22.26%,脲酶、磷酸酶和过氧化氢酶活性略高于E2。从现目前研究结果看,采伐干扰有利于改善林地水热条件,提高土壤酶活性,加速养分循环,尤其以保留采伐剩余物的效果为好。

灌溉定额和绿肥交互作用对小麦/玉米带田产量和养分利用的影响

【目的】研究灌溉定额、绿肥及其交互作用对河西绿洲灌区带田小麦、玉米产量和养分利用的影响,探寻适合灌区带田的水肥管理模式。【方法】试验采用裂-裂区设计,主区处理为灌溉定额,设三个水平为4500、6000和7500 m^3/hm^2;裂区处理为绿肥,设两个水平为不种绿肥和种植绿肥;裂-裂区处理为化肥,设两个水平,为不施化肥和施用化肥,化肥处理氮、磷、钾肥料用量分别为N 525 kg/hm^2、P2O5 150 kg/hm^2、K2O 90kg/hm^2。【结果】与4500 m^3/hm^2的灌溉定额相比,6000 m^3/hm^2和7500 m^3/hm^2的灌溉定额极显著增加了小麦和玉米的籽粒产量及其收获指数,增加了小麦和玉米籽粒的氮磷钾吸收量及其养分收获指数,小麦籽粒产量形成的氮生理效率和玉米籽粒产量形成的氮磷钾生理效率;极显著降低了小麦百公斤籽粒氮需求量和玉米百公斤籽粒氮磷钾需求量。绿肥种植与否对小麦、玉米籽粒产量均没有显著影响。种植绿肥极显著降低了玉米籽粒的收获指数和钾收获指数。灌溉定额4500 m^3/hm^2与种植绿肥交互作用下,玉米磷收获指数最低;灌溉定额6000m^3/hm^2与种植绿肥交互作用下玉米磷收获指数最高。种植绿肥处理显著增加了玉米百公斤籽粒氮磷钾需求量,显著降低了玉米百公斤籽粒磷钾生理效率。4500 m^3/hm^2灌溉定额下种植绿肥进一步加剧了干旱的胁迫程度,导致玉米百公斤籽粒氮、磷需求量显著增加,对钾的需求量极显著增加,磷生理效率显著下降,钾生理效率极显著下降。【结论】灌溉定额是河西绿洲灌区带田小麦玉米籽粒产量和收获指数、籽粒氮磷钾吸收量和氮磷钾收获指数、百公斤籽粒氮磷钾需求量和氮磷钾生理效率的决定因素。亏缺灌溉定额(4500 m^3/hm^2)下,种植绿肥会降低小麦/玉米带田籽粒产量及肥料利用效率。在6000 m^3/hm^2的灌溉定额下,建议河西绿洲灌区小麦/玉米带田应配合种植绿肥,提高产量和肥料效益。

不同施氮水平对小麦氮素利用及土壤养分的影响

为了探讨小麦氮素利用与产量之间的调控关系,以济麦22为供试材料,通过田间试验研究了不同施肥处理对小麦氮素利用及土壤养分的影响。结果表明,与不施肥相比,施有机肥显著提高了小麦的穗数、穗粒数和千粒重,施用有机肥(鸡粪)和有机肥(尾菜+秸秆)与不施肥相比小麦产量分别提高24.04%~44.98%和26.54%~47.48%。不论是单施化肥、有机肥还是有机肥化肥配施,与不施肥相比均能提升小麦的收获指数,同时提高小麦种植土壤的有机质和速效养分含量,其中有效磷含量可以提高44.02%~85.73%。不论是单施化肥、有机肥还是有机肥化肥配施均可提高小麦产量、氮收获指数和土壤养分含量,其中以有机肥(尾菜+秸秆)FM50处理效果最好。

沙区微区集水过程及植被效应研究进展

在界定沙区微区概念的基础上,分析了沙区微区集水的形成、转化以及对干旱沙区生态水文方面的重要作用,综述了国内外对微区集水在土壤水文、土壤发育和微区植被生长等方面的研究动态以及沙区微区集水在农林业和生态修复上的应用,指出沙区微区生态水文过程今后的研究重点在于对微区水文过程做出更加准确的量化分析,提出沙区具有完整意义的水文模型,为准确定量评价沙区水分循环和生态恢复提供理论依据。

植被砍伐对土壤养分的影响

研究了不同砍伐频率下，香港、深圳和鹤山研究样地山坡地Ｎ、Ｐ、Ｋ含量的差异．不同采样地之间，养分全量和有效量差异显著．在尚未砍伐的山坡地，土壤养分含量显著高于经常砍伐的山坡地．未伐土壤的Ｎ含量顺序为香港样地＞深圳样地＞鹤山样地．下层土壤Ｐ的含量高于上层土壤．深圳样地常代土壤养分含量高于鹤山．结果建议采用最适砍伐频率和在最适季节砍伐，以便减少砍伐产生的不利影响．

可作为饲料的水稻绿色营养体的营养素产量分析

The suitable harvest period, nutritive components and nutrient yields of 12 cultivars/combinations of indica rice as green feed were studied in 1994-1995. The result showed that the average outputs of dry matter, crude protein, fat and carbohydrate of the vegetative mass of rice (green feed) were 150. 4%, 243. 1 %, 207. 7% and 104. 9 % as comparing with those of rice grain. The days to harvesting were 20-- 28 d shorter in green feed than that of rice grain. In those tested c u it ivars /combinat ions, Xie yo u 2 8 8, Shanyou 48-2and Xieyou 210 would be good as green feed, and the suitable harvest period is in late booting to heading stage.

贵州旱地菜-菜-菜模式对土壤微生物区系和氮素养分的影响

为探讨贵州旱地菜-菜-菜一年三熟高效种植模式对土壤微生物区系和氮素养分的影响,对大方县连续3年蔬菜高效种植模式下的土壤微生物区系和氮素养分的变化进行分析。结果表明：与农民传统模式相比,蔬菜高效种植模式短期内（3 a左右）土壤微生物总数增加2.44~2.92倍,细菌总数占微生物总数的百分率净增加0.09%~0.21%,土壤全氮、硝态氮无明显差异,碱解氮有增加的趋势,平均增加9.0%~50.6%,土壤脲酶活性无明显差异。两种种植模式下土壤铵态氮与脲酶活性在一定范围内有较好的相关性（R2=0.706~0.940）。

集雨绿化系统现状及展望

集雨绿化系统主要以土壤水分为纽带,把土壤 植物 大气这个连续的系统统一为一个有机整体.讨论目前在绿化方面正面对的土壤干化问题、土壤植被群落类型以及造林密度现存的问题.集雨绿化系统减少了对最限制植物生长的土壤水分因子的影响,是目前进行植被建设的比较优化的系统.

宁南旱区沟垄集雨结合覆盖对土壤水热肥与马铃薯产量的影响

为探明不同沟垄集雨结合覆盖模式对土壤水热肥特性与旱作马铃薯产量的影响,于2015—2016年在宁南旱区连续两年设置6种沟垄集雨结合覆盖模式定位试验[垄上覆盖塑料地膜,沟内分别覆盖塑料地膜(PP)、玉米秸秆(PS)、生物降解地膜(PB)、麻纤维地膜(PF)、液态地膜(PL)和沟不覆盖(PN)],以平作不覆盖为对照(CK),研究其对土壤水分、温度、养分及马铃薯产量的影响。沟垄集雨结合覆盖模式可显著提高全生育期平均0~200 cm层土壤贮水量,以PS处理的保墒效果最佳。PP处理对马铃薯生育期土壤温度(0~25 cm)具有显著的增温效果,而PS处理降温效果显著。与试验处理前相比,2年马铃薯收获期不同沟垄集雨结合覆盖模式下0~40 cm层土壤有机碳、全氮、碱解氮、速效磷含量均显著提高,而速效钾含量显著降低,与对照相比均显著提高,其中以PS处理增幅最大。沟垄集雨结合覆盖模式能显著提高马铃薯产量和商品薯率,其中以PS和PP处理最高,PB、PF和PL处理次之,而PN与CK无显著差异。通过相关分析及通径分析发现,土壤水分、有机碳及温度是制约马铃薯高产的重要因子。垄覆地膜沟覆秸秆处理可显著改善旱作土壤水热肥环境,提高马铃薯产量,在宁南旱区马铃薯高产栽培中具有一定的应用价值。

不同降雨下旱地油菜节水节肥技术对土壤养分及酶活性的调控效应

为探讨沟垄集雨、秸秆覆盖和减量缓释肥节水节肥技术对油菜生产土壤养分及酶活性的调控效应,在大田定位试验条件下,设置农民习惯栽培(平作+常规肥)、节水栽培Ⅰ(秸秆覆盖+常规肥)、节水栽培Ⅱ(沟垄集雨+常规肥)、节肥栽培(平作+减量缓释肥)、双节栽培Ⅰ(秸秆覆盖+减量缓释肥)和双节栽培Ⅱ(沟垄集雨+减量缓释肥)6种水肥措施,比较分析2016-2017年(多雨年份)和2017-2018年(季节性干旱年份)2种不同降水年型下油菜节水节肥技术对土壤养分及酶活性的影响。结果表明:降水异常偏多对油菜生长的影响大于季节性干旱;双节技术在多雨年型下较习惯栽培增产效应显著,在季节性干旱年型下亦能稳产;在不同降水年型下,双节技术较习惯栽培能提高土壤pH和有机质含量,减少了土壤氮素淋溶损失,保持速效养分稳定释放,同时,能延迟脲酶释放,增加土壤碱性磷酸酶、蔗糖酶、纤维素酶活性,提高作物肥料利用效率及保持土壤肥力,更利于环境保护。综上,单一的节水或节肥技术无法满足西南旱地油菜生产需要。通过秸秆覆盖和沟垄集雨与缓释肥集成的双节技术,能适应不同降水年型下的油菜生产并兼顾环境效应,实现增产与环保的双赢目标。

杨树采伐剩余物施用对土壤养分和二氧化碳释放的影响

【目的】探索施用杨树Populus采伐剩余物对土壤养分和二氧化碳(CO_(2))释放的影响,为其潜在利用提供参考。【方法】以杨树树枝、树皮、树叶和水稻Oryza sativa秸秆等4种农林废弃物为生物质原料,根据杨树人工林单位面积凋落物量,以2%质量分数(以烘干土质量计)均匀混入新鲜土壤,25℃恒温培养箱中暗培养180 d。控制培养期间土壤含水量为田间持水量的60%。测定不同处理下土壤微生物生物量碳(MBC)、微生物生物量氮(MBN)、无机氮[铵态氮(NH_(4)^(+)-N)和硝态氮(NO_(3)^(−)-N)]、有效磷(AP)、速效钾(AK)等质量分数以及CO_(2)日释放速率和累积释放量。【结果】①4种生物质原料施用显著影响土壤微生物生物量及土壤氮磷钾的有效性(P<0.05)。相比对照,杨树树枝、树皮、树叶和水稻秸秆处理的土壤MBC质量分数分别增加了50%、31%、80%和109%,土壤MBN质量分数分别增加了54%、40%、72%和203%。施用杨树树皮和树枝土壤的NH_(4)^(+)-N质量分数从大到小依次为对照、秸秆处理、树叶处理、树皮处理、树枝处理。土壤AP质量分数以树枝处理最高,AK质量分数以秸秆处理最高。②不同处理的土壤CO_(2)日释放速率均表现为初期较快,中期逐渐减缓,后期趋于稳定。培养期间,秸秆处理的土壤CO_(2)累积释放量最高,显著高于其他处理(P<0.05),其次为杨树树叶,不同处理间差异显著(P<0.05)。③相关性分析表明:生物质原料的性质与土壤微生物生物量、土壤养分和CO_(2)释放量存在显著相关性。其中土壤微生物生物量与生物质原料的全氮、全磷、全钾显著正相关(P<0.05),与全碳和碳氮比显著负相关(P<0.05);土壤CO_(2)日释放速率与土壤MBC、MBN、NH_(4)^(+)-N、AP和AK均显著正相关(P<0.05),但与NO_(3)^(−)-N呈极显著负相关(P<0.01)。【结论】从土壤养分和环境效应综合考量,杨树采伐剩余物的施用能提高土壤有效态的氮磷钾等养分,相对减少碳排放。