黄土高原半干旱偏旱区苜蓿-粮食轮作土壤水分恢复效应

该文测定和分析了黄土高原半干旱偏旱区不同生长年限苜蓿草地以及轮作不同年限粮食作物后0～1000cm深层土壤水分变化规律。结果表明:随着苜蓿生长年限的延长,苜蓿草地土壤干层厚度逐渐增加,3年生苜蓿草地土壤干层深度达到760cm,6、7、10年生苜蓿草地土壤干层深度均超过1000cm,6年生苜蓿地1000～1500cm土层仍为干燥层,土壤平均湿度为9.68%;采用草粮轮作能明显减小苜蓿草地干层的厚度和范围,0～1000cm土壤水分较10年生苜蓿草地都有不同程度的恢复,轮作2、6、8、12和18a粮田平均土壤水分恢复速率25.2mm/a,年均累积恢复土层厚度123.1cm,0～300cm土层水分恢复程度较高,且轮作年限愈长,土壤水分恢复效果越好,轮作18a粮食作物后0～660cm土层土壤水分恢复量达到了531.1mm;苜蓿草地适宜翻耕年限为5～6a,且6年生苜蓿草地0～1000cm土壤水分恢复到当地土壤稳定湿度值需要23.8a,该地区适宜的苜蓿-粮食轮作模式为"5～6年生苜蓿→24年粮食作物"。

黄土高原半干旱区苜蓿草地土壤干燥化特征与粮草轮作土壤水分恢复效应

实地测定了黄土高原半干旱区固原不同生长年限苜蓿草地和连作8a苜蓿草地翻耕轮作不同年限粮食作物后深层土壤水分特征,分析了苜蓿草地土壤干燥化特征和粮草轮作对土壤水分的恢复效应。结果表明:(1)苜蓿连作1a、5a、8a和12a等4类苜蓿草地0~1000cm土层平均土壤湿度值为6.6%,平均土壤水分过耗量702.8mm,平均土壤干燥化速率147.1 mm/a,达到强烈干燥化程度,苜蓿连作5a土壤干层深度超过1000cm,苜蓿连作8a土壤干层深度超过1360cm,苜蓿草地合理利用年限为7a。(2)连作8a苜蓿草地翻耕并轮作4~7a和25a粮食作物等5类粮田0~1000cm土层土壤湿度介于6.74%~11.95%,土壤贮水量恢复值介于210.6~887.3mm,平均土壤水分恢复速率为80.8mm/a。轮作6a后粮田土壤干层轻度恢复程度以上深度达到1000cm。通过粮草轮作使苜蓿草地土壤湿度恢复到当地土壤稳定湿度需要13a以上。黄土高原半干旱区适宜的粮草轮作模式为:7a苜蓿→13a粮食作物。

La migración de cultivos de granos como indicador del cambio climático 1941 - 93 en la región pampeana argentina

p.171-176

Climate change modelling and its roles to chinese crops yield

Climate has been changing in the last fifty years in China and will continue to change regardless any efforts for mitigation. Agriculture is a climate-dependent activity and highly sensitive to climate changes and climate variability. Understanding the interactions between climate change and agricultural production is essential for society stable development of China. The first mission is to fully understand how to predict future climate and link it with agriculture production system. In this paper, recent studies both domestic and international are reviewed in order to provide an overall image of the progress in climate change researches. The methods for climate change scenarios construction are introduced. The pivotal techniques linking crop model and climate models are systematically assessed and climate change impacts on Chinese crops yield among model results are summarized. The study found that simulated productions of grain crop inherit uncertainty from using different climate models, emission scenarios and the crops simulation models. Moreover, studies have different spatial resolutions, and methods for general circulation model (GCM) downscaling which increase the uncertainty for regional impacts assessment. However, the magnitude of change in crop production due to climate change (at 700 ppm CO2 eq correct) appears within ±10% for China in these assessments. In most literatures, the three cereal crop yields showed decline under climate change scenarios and only wheat in some region showed increase. Finally, the paper points out several gaps in current researches which need more studies to shorten the distance for objective recognizing the impacts of climate change on crops. The uncertainty for crop yield projection is associated with climate change scenarios, CO2 fertilization effects and adaptation options. Therefore, more studies on the fields such as free air CO2 enrichment experiment and practical adaptations implemented need to be carried out

Consorciação de braquiárias com milho outonal em plantio direto sob pivô central

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Época de semeadura, produção e qualidade fisiológica de sementes de milheto

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Intervalo hídrico ótimo e compactação do solo com cultivo consorciado de milho e braquiária

O cultivo consorciado entre a espécie forrageira e a cultura produtora de grãos garante a produção de forragem no outono-inverno, além de palha para cobertura do solo em sistema semeadura direta. O aporte de matéria seca radicular no perfil do solo possibilita a melhoria da qualidade estrutural do solo. Objetivou-se com este experimento verificar as alterações nos atributos físicos e físico-hídricos do solo com o cultivo de milho solteiro e consorciado com Brachiaria brizantha. O experimento foi conduzido na Fazenda Experimental Lageado (UNESP, Botucatu-SP), entre os anos agrícolas de 2002/2003 e 2003/2004. Foram coletadas amostras com estrutura preservada de solo, por meio de anéis volumétricos, nas camadas de 0 a 20 e 20 a 40 cm de profundidade, em trincheiras abertas em parcelas cultivadas com milho e mantidas em pousio na entressafra, bem como em parcelas cultivadas com milho consorciado com B. brizantha na linha de semeadura, mantendo a forrageira para pastagem após a colheita do milho. A partir dessas amostras, foi avaliado o Intervalo Hídrico Ótimo (IHO), por meio de curvas de resistência à penetração e de retenção de água, em amostras com diferentes densidades do solo. O cultivo solteiro de milho na safra de verão é suficiente para melhorar as características físicas e estruturais do solo na camada de 0 a 20 cm. O cultivo de braquiária em consórcio com o milho por dois anos consecutivos melhora as condições físicas e estruturais do solo na camada de 20 a 40 cm, com redução da resistência mecânica à penetração e aumento da densidade crítica do solo.

Effect of temperature on development and population growth of Acarophenax lacunatus (Cross and Krantz) (Prostigmata: Acarophenacidae) on Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

The parasitic mite Acarophenax lacunatus kills the eggs upon which it feeds and seems to have potential as a biological control agent of stored grain pests. The lack of biological studies on this mite species led to the present study carried out in laboratory conditions at eight different temperatures (ranging from 20 to 41°C) and 60% relative humidity using Rhyzopertha dominica as host. The higher the temperature, the faster: (1) the attachment of female mites to the host egg (varying from 1 to 5 h); (2) the increase in body size of physogastric females (about twice faster at 40°C than at 20°C); and (3) the generation time (ranging from 40 to 220 h). In addition, the higher the temperature, the shorter the maximum female longevity (ranging from about 75 to 300 h). The two estimated temperature thresholds for development of A. lacunatus on R. dominica were 18 and 40°C. The average number of female and male offspring per gravid mite were 12.8 and 1.0, respectively, with sex ratios (females/total) ranging from 0.91 to 0.94 (maximum at 30°C). The net reproductive rate and intrinsic rate of increase also presented maximum values at 30°C (12.1 and 0.04, respectively).

Crescimento e produtividade da mamoneira iac 2028 na safrinha em função da população de plantas em espaçamento reduzido

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Perda de matéria seca em grãos de milho submetidos a sistemas de secagem natural e artificial

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Curvas de progresso de doenças foliares do milho, sob diferentes tratamentos fungicidas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Oat Variety Trials, 2010 and 2011

Oat is the major spring-sown, small grain crop in Iowa. Spring-sown small grains can be used for grain and straw production, as a companion crop to establish hay and pastures, or as a source of early-season forage as hay or haylage. Because small grains generally mature before the end of July, a forage legume, cover crop, or green manure crop can follow oats, or animal manure can be spread on the field in which oats were grown.

Adubação de sistemas: antecipação de adubação nitrogenada para a cultura do milho em integração lavoura-pecuária

Traditionally in no-tillage systems, fertilization is done to the catch crop. In general nutrient cycling in crop systems has not been treated as an important tool in the process of nutrient supplying for plants. The type and the condition in which vegetable residuesis decomposed can affect the efficiency of nutrient cycling.This study assessed the effect of anticipated nitrogen fertilization in crop-livestock systems on cultivated cornproduction, rate ofnutrient release from plant residue, and theN-minerallevels of soil. The study was carried out in the city Abelardo Luz (SC) in a Clayey Oxisol. The experimental design was a randomized block design with three replications. The treatments were arranged in a 2 x 2 factorial arrangement. The first factor was N Fertilization Time: in the N-Pasture level, nitrogen (200 kg ha-1 N) and N-Grains level, no nitrogen was applied. The second factor was the Grazing Height, characterized by two sward heights of oat at 15 cm (Low Height Pasture) and at 30 cm (High Height Pasture). Corn hybrid ‘Máximus’ was sowed in 10thOctober, 31 days after the removal of animals. In the twelve resulting plots from the combination of treatments on pasture phase (N Fertilization Time x Grazing Height) rates of N-fertilizer (0, 100, 200 e 300 Kg ha-1 of N) as urea were allocated in the split plot.We conclude that anticipated N fertilization of winter cover crop pasture to provide high-quality forage and carry-over N to the subsequent corn crop and may eventually replace side drees nitrogen fertilization on corn and can improve overall N fertilizer efficiency use in integrated crop-livestock systems.The rate of K release from plant residues is very fast, releasing large quantities in the first days after plant desiccation.Despite of considerably high nitrogen dose used in both the pasture and at the grain crop it was not observed nitrate leaching risks during the study period.

Subsoil constraints in Vertosols: Crop water use nutrient concentration, and grain yields of bread wheat, durum wheat, barley, chickpea and canola

Single or multiple factors implicated in subsoil constraints including salinity, sodicity, and phytotoxic concentrations of chloride (Cl) are present in many Vertosols including those occurring in Queensland, Australia. The variable distribution and the complex interactions that exist between these constraints limit the agronomic or management options available to manage the soil with these subsoil constraints. The identification of crops and cultivars adapted to these adverse subsoil conditions and/or able to exploit subsoil water may be an option to maintain productivity of these soils. We evaluated relative performance of 5 winter crop species, in terms of grain yields, nutrient concentration, and ability to extract soil water, grown on soils with various levels and combinations of subsoil constraints in 19 field experiments over 2 years. Subsoil constraints were measured by levels of soil Cl, electrical conductivity of the saturation extract (ECse), and exchangeable sodium percentage (ESP). Increasing levels of subsoil constraints significantly decreased maximum depth of water extraction, grain yield, and plant-available water capacity for all the 5 crops and more so for chickpea and durum wheat than bread wheat, barley, or canola. Increasing soil Cl levels had a greater restricting effect on water availability than did ECse and ESP. We developed empirical relationships between soil Cl, ECse, and ESP and crop lower limit (CLL) for estimating subsoil water extraction by 5 winter crops. However, the presence of gypsum influenced the ability to predict CLL based on the levels of ECse. Stronger relationships between apparent unused plant-available water (CLL - LL15; LL15 is lower limit at -1.5 MPa) and soil Cl concentrations than ESP or ECse suggested that the presence of high Cl in these soils most likely inhibited the subsoil water extraction by the crops. This was supported by increased sodium (Na) and Cl concentration with a corresponding decrease in calcium (Ca) and potassium (K) in young mature leaf of bread wheat, durum wheat, and chickpea with increasing levels of subsoil constraints. Of the 2 ions, Na and Cl, the latter appears to be more damaging than the former, resulting in plant dieback and reduced grain yields.

Crop sequences to manage soil pathogens and increase northern grain production

This is part of a GRDC funded project led by Dr Jeremy Whish of CSIRO Ecosystem Sciences. The project aims to build a root-lesion nematode module into the crop growth simulation program APSIM (Agricultural Production Systems Simulator). This will utilise existing nematode and crop data from field, glasshouse and laboratory research led by Dr John Thompson. New data will be collected to validate and extend the model.