铁茬高产夏玉米品种产量和植株性状间关系分析

为选择铁茬条件下夏玉米的适播品种，试验采用单因素随机区组方法对20个玉米品种（品系）在小麦收获后铁茬播种条件下的产量、生物产量、经济系数和穗部性状等进行了研究。结果表明，燕202、浚单22、雅玉12、郑单958和矮225在中等肥力土壤下可以达到9000kg/hm2高产水平，穗数>60000穗/hm2、穗粒数420~515粒/穗、公顷粒数>2778万粒、千粒重>280g、生物产量>16300kg/hm2、经济系数>0.54、出米率88±1.34%。大穗型品种、特别是平展大穗型品种无高产优势。相关分析表明，产量与经济系数、收获穗数、公顷粒数、生物产量成极显著正相关。中小穗型品种穗粗、穗行数与产量显著正相关对产量影响较大；大穗型品种产量与穗粗为负相关，且产量与穗长、行粒数和出米率关系最为密切。     

5个玉米人工合成群体主要性状育种潜势分析

对5个玉米人工合成群体主要性状表现、杂种优势以及配合力进行了研究。结果表明，群体内个体间均存在较丰富的遗传变异，群体间主要性状及其配合力差异更为明显，其中群体GP-5和GP-3植株穗位高低适中，主要产量性状及其GCA表现较好，优良个体出现频率较高，比对照高产的组合出现次数较多，具有较大改良利用潜势；群体GP-4虽主要产量性状均值偏低，GCA正向效应值偏小，但植株较矮，穗位较低，比对照高产的组合出现次数较多，通过GCA改良和SCA选择有一定利用前景；群体GP-1和GP-2植株穗位偏高，主要产量性状的GCA均为负值，育种潜力不大。     

普通玉米新品种比较试验

对11个普通玉米新品种进行比较试验，结果表明：S986、YA0682、宝玉099综合农艺性状表现优良，高产、适应性强，适宜在合浦县推广种植。     

玉米秸秆整株还田对小麦生长发育及产量的影响

简述了玉米整株还田技术、所需配套机具和工艺特点以及对小麦生长发育及产量效应的影响,玉米秸秆整株还田经过1年腐解其腐解率达90％以上。玉米整株还田耕深20cm,秸秆在8cm土层以下覆盖率达95％以上,能保证冬小麦播种质量,小麦基本苗及分蘖测定分别比粉碎还田增加23株和0.2个,小麦生育期干物质量及千粒重分别增加8.95％和1.33％,小麦产量提高3.81％。     

玉米秸秆还田对塑料大棚蔬菜连作土壤改良效果研究(初报)

研究了施用玉米秸秆对蔬菜塑料大棚连作土壤的改良效果及其对黄瓜生长的效应。结果表明：施用０．４％～１．２％玉米秸秆能明显提高土壤有机质含量和孔隙度、降低土壤容重，改善耕层的通透性。秸秆处理还可降低土壤的电导度（ＥＣ），遏制土壤次生盐渍化。施用玉米秸秆促进了黄瓜生产，春茬黄瓜比对照增产５．０％～１０．１％，秋茬黄瓜比对照增产１１．７％～２６．９％。     

施用秸秆堆腐肥对黑土农田养分及玉米产量的影响研究

试验研究表明应用秸秆腐解剂可快速堆腐秸秆 ,黑土农田施用充分腐熟的秸秆肥配施NPK化肥 ,耕层土壤平均年提高有机质 0 .4g/kg ,全N 0 .18g/kg ,速效氮 9.93mg/kg ,速效磷 1.8mg/kg ,速效钾 4mg/kg ,土壤容重年降低0 .0 2g/cm3 ,玉米增产 15 .7%。     

Winter cover cropping influence on nitrogen mineralization,presidedress soil nitrate test,and corn yields

The mineralization and availability of cover crop N to the succeeding crop are critical components in the management of soil N to reduce N leaching. The effects of several leguminous and non-leguminous cover crops on soil N availability, N mineralization potential, and corn (Zea mays L.) yield were examined. The cover crops had variable effects on soil N availability and corn yield and N uptake. Because of the rapid mineralization of the cover crops following incorporation, the inorganic N levels in the soil sampled in mid-May 1992 (4 weeks after incorporation of cover crops), rather than the potentially mineralizable N, rate constants, initial potential mineralization rate, or cumulative N mineralized over 14 weeks, correlated well with N concentrations, C:N ratios, or the N added in the cover crops. However, the inclusion of potentially mineralizable N with inorganic N in a multiple regression improved the variability in the corn yield and the N uptake accounted for. Since extensive mineralization had occurred before the 21 May sampling, the potentially mineralizable N was affected more by the soil organic N and C than by the N concentrations of the cover crops. The presidedress NO₃ ^--N test levels were well predicted by the inorganic and potentially mineralizable N (R ²=0.89, P<0.01), although the test levels were better in predicting corn yield and N uptake. If the available soil N test needs to be made earlier than recommended by the presidedress NO₃ ^--N test, both inorganic and potentially mineralizable N are needed to better predict the corn yield and N uptake in the soils.     

Effect of long-term liquid pig manure application on atrazine mineralization in a soil cultivated with maize

Soil samples were collected in plots from a field experiment in maize monoculture receiving 0, 60 and 120 m³ ha^-1 liquid pig manure (LPM) for 19 years. Soils were sampled from the 0- to 20-cm layer in August and October 1997 and in June, July and September 1998. Subsurface samples were also evaluated in September 1998. Laboratory soil radiorespirometry was used to evaluate atrazine mineralization using [U-ring-¹⁴C]-atrazine mixed with commercially available product. The effect of atrazine dose (50, 100 and 500 mg atrazine kg^-1 soil) was evaluated on soils sampled in August 1997. For the other sampling dates, the soils were spiked with 50 mg atrazine kg^-1 soil. No LPM dose effect on atrazine mineralization was obtained in the different experiments. Increasing atrazine dose to 500 mg kg^-1 decreased significantly the mineralization rate (R_i) and the maximum of atrazine mineralized (MAX), while the time needed to mineralize 50% of MAX (DT-50%) was not significantly affected. Sampling time had a significant effect on atrazine mineralization. Atrazine mineralization in the soils sampled in June 1998 showed lower R_i and MAX than in the soils sampled at the other dates. Atrazine mineralization in subsurface soils (20–60 cm) was very variable and quite high in some samples. This may be due to atrazine pre-exposure in subsoils resulting from atrazine deep movement by preferential flow.     

Cropping systems effects on snowmelt losses of solids and associated organic carbon

Increase in alfalfa (Medicago sativa L.) production for energy (gasification of stems) and protein supplement (from leaves) has been proposed for the upper Midwestern United States, an area where corn (Zea mays L.) in rotation with soybean (Glycine max L.) is the predominant crop sequence. This study was undertaken to assess the impact on runoff and water quality, especially for the loss of oxygen demanding material with snowmelt. Four field size watersheds were instrumented at Morris, Minnesota, USA on a rolling prairie landscape. Snowmelt runoff from each watershed was measured with two flumes with overlapping ranges arranged in series. An automatic water sampler collected runoff samples for chemical analysis. Oxygen demand was used as a surrogate for reduced carbon. Water samples were analyzed for total solids, biochemical oxygen demand (BOD), and chemical oxygen demand (COD). Based on the results of snowmelt events of 1997, 1998, and 1999, the alfalfa fields yielded more runoff than corn-soybean fields. The loss of total solids was more consistent from alfalfa fields. Total solids losses interacted with crop and year. Compared to alfalfa fields losses were less following soybeans and greater following corn. On average losses were similar between alfalfa and corn-soybean fields. Runoff from alfalfa fields contained about four times more BOD than corn-soybean fields. Although not statistically significant due to only two replications, there was a similar trend for COD. This study shows that although losses of total solids in snowmelt from alfalfa fields was similar to corn-soybean fields, there can be increased losses of oxygen demanding materials.     

Soil microbial activity,aggregation and nutrient responses to straw pulping liquor in corn cropping

The cereal and grass seed cropping systems of the Pacific northwestern USA generate a valuable fiber source for papermaking. Pulping straw with KOH produces black liquor, an organic waste effluent with potential as a K source and soil amendment. The objectives of this study were to determine if black liquor from wheat straw pulping with KOH improves soil quality including soil aggregation, microbial biomass and microbial activity, and corn yield. A 2-year field trial with a randomized complete block design was conducted with black liquor or KCl applied at 168 and 336 kg K ha⁻¹ at two sites, respectively, planted to corn in Central Washington. Black liquor applied at rates of 168 and 336 kg K ha⁻¹ slightly increased soil pH by 0.2 to 1.4 units and electrical conductivity by 0.0 to 0.8 dS m⁻¹ at both sites, and significantly increased soil test K compared to the nonamended control by 199 to 368 mg K kg⁻¹ soil in the top 5 cm at Paterson and by 44 to 200 mg K kg⁻¹ soil in the top 5 cm at Prosser. Corn had no yield response to the application of either K sources, black liquor, or KCl applied at both rates at both sites. Generally, black liquor applied at these rates increased soil dehydrogenase, β-glucosidase, and arylsulfatase activities, microbial biomass C, and soil wet stable macroaggregates in the top 5-cm soil at both sites. The results of this study suggest that the organic-rich waste liquor from wheat straw pulping with KOH may improve soil quality and soil test K without reducing crop productivity.