Maize Sowing Dates Research Articles

Optimised sowing date enhances crop resilience towards size-asymmetric competition and reduces the yield difference between intercropped and sole maize

Intercropping is becoming an attractive and profitable agricultural practice, and a growing body of literature investigate on the plant–plant interaction between intercrops. However, little is known on how sowing date alters interspecific interaction causing a yield difference between the intercropped and sole crop. A two-year field experiment was undertaken to investigate the impacts of varying competitive interaction on plant growth and grain yield of a maize/watermelon intercropping system. Both intercropped and sole maize were sown 28 days, 33 days and 38 days after a consistent transplanting date for watermelon to generate varying intensities of asymmetric competition between species in the maize/watermelon intercropping system. Growth patterns were monitored over two years and described with logistic growth curves. Compared with conventional sowing date, changes in maize sowing date significantly enhanced the intercropped maize grain yield by 21%–42%, but barely affected the sole maize yield, consequently reducing the yield difference between intercropped and sole maize. An earlier sowing date empowered the intercropped maize to reach the maximum absolute growth rate 11 days earlier, producing greater aboveground biomass and larger growth rate over its growing period, and thereby enhanced the maize resilience towards size-asymmetric competition derived from the presence of watermelon. Changes in the maize sowing date did not alter the fruit yield of intercropped watermelon in the most cases, but overmuch improvement in the aggressivity and growth rate of the maize sown on 13 June in 2014 caused a 16% reduction in fruit yield. We concluded that the yield difference can be reduced by adjusting the sowing date to manipulate plant–plant interaction between intercrops, and an optimal sowing date not only enhances crop growth but also brings on no penalty on companion crop yield.

Reduced irrigation increases the water use efficiency and productivity of winter wheat-summer maize rotation on the North China Plain

The groundwater table has fallen sharply over the last 30years on the North China Plain, resulting in a shortage of water for winter wheat irrigation. Reducing irrigation may be an important strategy to maintain agricultural sustainability in the region; however, few studies have evaluated the transition from conventional irrigation management practices to reduced irrigation management practices in the winter wheat-summer maize rotation system. Here, we compare the yield, water consumption, and water use efficiency of winter wheat-summer maize rotation under conventional irrigation and reduced irrigation on the North China Plain from 2012 to 2015. Reducing irrigation decreased the yield but increased the water use efficiency and significantly advanced the harvest date of winter wheat. As a result, the summer maize sowing date advanced significantly, and the flowering date subsequently advanced 2–8days, thus extending the summer maize grain-filling stage. Therefore, the yield and water use efficiency of summer maize were higher under reduced irrigation than conventional irrigation, which compensated for the winter wheat yield loss under reduced irrigation. In addition, under reduced irrigation from 2012 to 2015, the yield and water use efficiency advantage of the winter wheat-summer maize rotation ranged from 0.0 to 9.7% and from 4.1 to 14.7%, respectively, and water consumption and irrigated water decreased by 20–61mm and 150mm, respectively, compared to conventional irrigation. Overall, the reduced irrigation management practice involving no irrigation after sowing winter wheat, and sowing summer maize on June 7 produced the most favorable grain yield with superb water use efficiency in the winter wheat-summer maize rotation. This study indicates that reducing irrigation could be an efficient means to cope with water resource shortages while maintaining crop production sustainability on the North China Plain.

Sowing date and maize grain quality for dry milling

Abstract Argentina is the single exporter of non-gmo hard endosperm maize to the European Union, and is internationally known for its grain hardness. This special hard endosperm maize supply chain follows strict regulations to ensure a high quality grain. Specific values for test weight, flotation index, grain vitreousness, and screen retention are demanded by the dry milling industry. Central temperate Argentinean production system is currently changing to later sowings, and there is limited information on the effect of contrasting sowing dates over specific grain quality attributes of interest for the industry. In this study we explored the effects of delaying maize sowing dates from September-October to December on maize dry milling grain quality in the central temperate area. Eighteen commercial genotypes differing in grain hardness were sown during two growing seasons and two sowing dates. Measured traits were grain yield, individual grain weight, dry milling quality (test weight, floaters, vitreousness, 8 mm screen retention), and composition (oil, protein, starch). Grain yield varied significantly among genotypes (p

Maize grain yield components and source-sink relationship as affected by the delay in sowing date

Delaying maize (Zea mays L.) sowing date can diminish grain yields through reductions in the number, size and activity of growing grains (sink strength) and/or reductions in the assimilate supply (source capacity) to grains during the grain filling period. Whether the source capacity or the sink strength is the limiting factor for grain yield in late sown maize still remains unclear. Understanding source-sink relationships is relevant to optimize crop management practices, to identify critical processes for crop modelling and to develop breeding strategies. The objective of this work was to assess the effect of delays in maize sowing date on grain yield components and on the source-sink relationship during the grain filling period. Three well irrigated and fertilized maize field experiments were conducted at Balcarce, Argentina (37° 45′ S, 58° 18′ W; 130m a.s.l.) during 2009–10; 2010–11 and 2011–12 cropping seasons. Sowing dates ranged from October to January covering a broad range of the seasonal photo-thermal variation. Grain yield was affected by sowing date and varied from 1680gm−2 (early sowings) to 203gm−2 (late sowings). Grain number per unit area was reduced proportionally less than weight per grain as sowing date was delayed. Variations in grain yield were related to the harvest index, and were closely associated with dry matter accumulation during the post-silking period. The variation of source capacity was higher than that of sink strength during the grain filling period and the source/sink ratio decreased from early to late sowing dates. Results indicate that crop growth during the grain filling period was limited by the sink strength in early sowing dates and by the photosynthetic source capacity in the late ones.

Maize growing duration was prolonged across China in the past three decades under the combined effects of temperature, agronomic management, and cultivar shift.

Maize phenology observations at 112 national agro-meteorological experiment stations across China spanning the years 1981-2009 were used to investigate the spatiotemporal changes of maize phenology, as well as the relations to temperature change and cultivar shift. The greater scope of the dataset allows us to estimate the effects of temperature change and cultivar shift on maize phenology more precisely. We found that maize sowing date advanced significantly at 26.0% of stations mainly for spring maize in northwestern, southwestern and northeastern China, although delayed significantly at 8.0% of stations mainly in northeastern China and the North China Plain (NCP). Maize maturity date delayed significantly at 36.6% of stations mainly in the northeastern China and the NCP. As a result, duration of maize whole growing period (GPw) was prolonged significantly at 41.1% of stations, although mean temperature (Tmean) during GPw increased at 72.3% of stations, significantly at 19.6% of stations, and Tmean was negatively correlated with the duration of GPw at 92.9% of stations and significantly at 42.9% of stations. Once disentangling the effects of temperature change and cultivar shift with an approach based on accumulated thermal development unit, we found that increase in temperature advanced heading date and maturity date and reduced the duration of GPw at 81.3%, 82.1% and 83.9% of stations on average by 3.2, 6.0 and 3.5days/decade, respectively. By contrast, cultivar shift delayed heading date and maturity date and prolonged the duration of GPw at 75.0%, 94.6% and 92.9% of stations on average by 1.5, 6.5 and 6.5days/decade, respectively. Our results suggest that maize production is adapting to ongoing climate change by shift of sowing date and adoption of cultivars with longer growing period. The spatiotemporal changes of maize phenology presented here can further guide the development of adaptation options for maize production in near future.

Effects of different crop years and sowing date on maize yield

We carried out the tests in the flood meadow soil formed on the alluvial cone of Nagykereki, Sebes-Körös belonging to the Bihar plane small region. The aim of the study was to analyse the effect of the different sowing date of maize on the yield trend based on a comprehensive study conducted for 6 years (2007–2012).
 The sowing date of maize hybrids is a factor that significantly influences yield, however, its effect is not significant in each crop year. In the years when the date of sowing has a modifying effect, the reliable yield level can be reached with optimal sowing date management (24 April).
 The advantage of early sowing (10 April) proved to be dominant in the year of 2012, the seeds were placed into the still wet soil therefore shooting was more balanced. Maize seeds sown at the time of optimal (24 April) and late (10 May) sowing dates were placed into the already dry soil, which deteriorated germination and the strength of early initial development that had an effect on the yield.

Use of the FAO AquaCrop model in developing sowing guidelines for rainfed maize in Zimbabwe

This paper presents a procedure in which the water-driven water productivity model AquaCrop was fine-tuned and validated for maize for the local conditions in Zimbabwe and then applied to develop sowing management options for decision support. Data from experiments of 2 seasons in Harare and from 5 other sites around Zimbabwe were used for the local calibration and validation of AquaCrop. Model parameters such as the reference harvest index (HIo); the canopy growth coefficient (CGC); early canopy decline and normalised biomass water productivity (WPb*) were adjusted during model calibration. Model performance was satisfactory after calibration with a Nash-Sutcliffe model efficiency parameter (EF = 0.81), RMSE = 15% and R2 = 0.86 upon validation. To develop sowing guidelines, historical climate series from 13 meteorological stations around Zimbabwe were used to simulate maize yield for 6 consecutive sowing dates determined according to criteria applicable in Zimbabwe. Three varieties and typical shallow and deep soil types were considered in the simulation scenarios. The simulated yield was analysed by an optimisation procedure to select the optimum sowing time that maximised long-term mean yield. Results showed that highest yields depended on the climate of the site (rainfall availability), variety (length of growing cycle) and soil depth (soil water storage capacity). The late variety gave higher mean yields for all sowing dates in the maize belt. Staggered sowing is recommended as a way of combating the effects of rainfall variability and as an answer to labour constraints.Keywords: biomass water productivity, AquaCrop, maize sowing dates, crop modelling

Multiple regression analysis for studied traits in intercropping of popcorn and cowpea

The goal of multiple regressions is to enable a researcher to assess the relationship between a dependent variable and several independent (predictor) variables. In order to determination of some popcorn yield characteristics with higher effect on yield an experiment was conducted as factorial based on RCB in Islamic Azad University of Tabriz. Studied factors included maize sowing dates (12 th , 19 th and 26 th May) and sowing percentage of cowpea as 12.5%, 25%, 37.5%, 50% and 100% of recommended density rate (5, 10, 15, 20 and 40 plants per square meter). Based on results weight of 300 seed in corn ranged from 33.6 g in intercropping of popcorn + cowpea with 50% of recommended density rate up to 39.5 g and 39.7 g in intercropping of the crops with 12.5% and 25% of recommended density, respectively. Weeds biomass in intercropping of the crops with 12.5% and 25% of recommended density rate experienced reduction of 4.5 g m -2 compared to the maize mono-cropping and 6 g m -2 compared to the mean of intercropping of the crops with 37.5% and 50% of recommended density rate. Increasing of cowpea density when intercropped with maize caused to earlier flowering. The stepwise regression analysis verified that the LAI, 300 seed weight and weeds biomass had a marked increasing effect on the corn seed yield in intercropping with cowpea.

A Dutch field survey on fungal infection and mycotoxin concentrations in maize

Mycotoxins are secondary metabolites produced by fungi that can cause adverse health effects. Due to climate change, temperatures are expected to rise and changes in rainfall patterns are foreseen. These developments may increase fungal occurrence and mycotoxin concentrations in maize. It is therefore useful to monitor mycotoxin levels in maize and record the accompanying agronomic factors and weather parameters. This paper describes a field survey in the Netherlands in which information on soil, cultivar, green manure, tillage as well as sowing, emergence, flowering and harvest dates of silage maize were collected from 148 growers. A small number of these growers (42 in total) were visited to collect maize samples revealing that 50% of the samples were contaminated with Fusarium species and mycotoxins were detected in 25% of the samples. The Fusarium species that was most commonly found was F. crookwellense followed by F. graminearum, F. culmorum, F. sporotrichiodes and F. equiseti. In total 31 mycotoxins were analysed. The predominant mycotoxins present were (sum of 3 and 15)-acetyl-DON and nivalenol; other mycotoxins found were alternariol, beauvericin, deoxynivalenol, diacetoxyscirpenol, moniliformin and zearalenone. Nivalenol was present in concentrations up to 1670 µg kg–1 and acetylated DON was usually present at higher concentrations than DON. Statistical analysis of the current data showed no correlation between mycotoxins present and agronomic factors recorded. Field studies as described in this paper are useful and need to be continued in the future in order to observe trends in mycotoxin occurrence.

Mitigation of climate change impacts on maize productivity in northeast of Iran: a simulation study

Development and evaluation of mitigation strategies are fundamental to manage climate change risks. This study was built on (1) quantifying the response of maize (Zea mays L.) grain yield to potential impacts of climate change and (2) investigating the effectiveness of changing sowing date of maize as a mitigation option for Khorasan Province which is located in northeast of Iran. Two types of General Circulation Models (GCM: (United Kingdom Met Office Hadley Center :HadCM3) and (Institute Pierre Simon Laplace: IPCM4)) and three scenarios (A1B, A2 and B1) at four locations (Mashhad, Birjand, Bojnourd and Sabzevar) employed in this study. Long Ashton Research Station-Weather Generator (LARS-WG) was employed for generating the future climate. The Cropping System Model (CSM)-CERES-Maize was used for crop growth simulation under projected climate conditions. The results showed the simulated grain yields of maize gradually would decrease (from −1% to −39%) during future 100 years compared to baseline under different scenarios and two GCM at all study locations. The simulation results suggested that delayed sowing date from May to June at all study locations, except Sabzevar location is the most effective mitigation option for avoiding thermal stress at end of growth period. In addition, shifting in sowing date to March or April will be beneficial in terms of obtaining higher yields in Sabzevar. Grain yield did not show special trend from north to south of Khorasan Province in the future climate. In general, change of sowing date may be quite beneficial to mitigate climate change impacts on grain yield of maize in northeast of Iran.

Making sense of yield trade-offs in a crop sequence: A New Zealand case study

Crop growth is driven by the capture and utilisation of solar radiation. The most productive crop sequences are those that maximise the interception and use of solar radiation. However, there are yield trade-offs because of the timing of transitions between successive crops. A longer duration of one crop will mean that the following crop is sown later and will therefore produce a lower yield. Maximising the yield of a sequence involves a compromise between the yields of successive crops. We describe a case study of a forage cropping rotation in New Zealand, demonstrating how simulation models can be used to define the best compromise between the yields of successive crops, and thereby maximise the total yield of the full sequence. A case study using a series of long-term simulation experiments for four diverse environments in New Zealand was undertaken in a continuous, summer maize – winter cereal, cropping sequence. Maize sowing dates and hybrid durations, and cereal sowing and harvest times were varied systematically. The actual simulated crop and sequence yields varied from site to site, but there was a consistent trend identifying the most productive combinations of sowing date and hybrid duration. The sequence of comparatively late sowing date of maize (1 December) and a long-season hybrid maximised the total yield of the sequence. The highest sequence yields were achieved by balancing the need to capture a high level of annual solar radiation and the need to have a large proportion of solar radiation captured by maize, which has the greater RUE in summer. This analysis illustrates how crop simulation models can be used to design and understand the processes that give the most productive cropping sequences.

Validation of a model relating yield loss to weed time of emergence and removal in traditional and early‐sown maize

Masin R, Berti A, Otto S & Zanin G (2010). Validation of a model relating yield loss to weed time of emergence and removal in traditional and early‐sown maize. Weed Research50, 120–126.SummaryIn northern Italy, there has been a tendency in recent years to advance maize sowing from mid‐April to mid‐March. This may lead to many agronomic advantages but can strongly influence weed flora composition, density, time of emergence, and crop and weed relative growth. Altering the maize sowing date thus requires a better understanding of the competitive relationship between crop and weeds. This study evaluates an existing model expressing crop yield as a function of maximum yield of the weed‐free crop, weed competitive load and time of weed emergence and removal. The model can predict the yield loss caused by mixed infestations with a single set of parameters. The aim of this study was to validate this model with independent data from experiments on early and traditionally sown maize, in support of the idea that the model is robust enough to be used as a prediction tool for forecasting yield losses in a variety of conditions created by different sowing dates. In traditional sowing, the plot of expected versus observed yields showed that the model gives a good fit. However, for early sowing, the model accuracy in predicting crop yields was improved when the curve intercepts were shifted by 60 growing degree days (d °C). This shift corresponded to the difference between the onset of weed emergence in traditional and early sowing, which suggests that weeds may be less competitive when maize is sown earlier.

Growth and yield of maize as influenced by sowing date and poultry manure application.

Two fields experiments were conducted in 2004 and 2005 at Evboneka in Edo State, Nigeria to determine optimum sowing date and poultry manure requirement of maize (Zea mays) for the forest ultisol location. We examined the biomass production and yield, besides growth parameters under three sowing dates (April 7, May 7 and June 7) and four levels of poultry manure (0, 2.5, 5.0 and 7.5 tonnes per hectare (tha-1)) in factorial arrangement fitted into randomized complete block design with three replications. Plant heights, leaf area index (LAI), days to 50% flowering and biomass were significantly affected by sowing date and poultry manure application. The plant height values ranged from 3.9 to 10.80 centimetre (cm) at two weeks after sowing (WAS) to 48.3 cm at six WAS, respectively for the three sowing dates and four levels of poultry manure combinations. Days to 50% flowering was increased when sowing was delayed and with increased in applied poultry level and it vary from 50 to 73 days after sowing. The corresponding value of biomass was 3.32 to 8.80 t ha-1 at final harvest. These parameters resulted in higher crop growth rate for April 7 sown plants treated with poultry manure giving higher grain yield and 1000-grain weight. The maximum grain yield of 5.77 t ha-1 and 1000-grain weight were obtained from April 7 sown plants treated with 5.0 t ha-1 of poultry manure indicating that the best sowing date and poultry level for growth and yield of maize in the rainforest ultisol.

Temperatura base para emissão de folhas e nós, filocrono e plastocrono das plantas daninhas papuã e corriola

Alexander grass (Brachiaria plantaginea) and Morning glory (Ipomoea triloba) are important weeds in annual crops. The phyllochron (time interval between the appearance of two successive leaves) and the plastochron (time interval between the appearance of successive nodes) are important parameters of plant development. Thermal time is used to express time in the phyllochron and in the plastochron, and in the calculation of thermal time the value of the base temperature is needed. The objective of this study was to estimate the base temperature for leaf and node appearance, the phyllochron and the plastochron for Alexander grass and Morning glory, respectively. Data used in this paper come from an experiment with maize sown in several dates, carried out in Santa Maria, RS, Brazil, during the 2005/2006 growing season. Two plants of Alexander grass and two plants of Morning glory were left to grow in each maize plot. The main stem Haun Stage (HS) in Alexander grass and the number of visible nodes in Morning glory were measured on a weekly basis. Using the Mean Square Error (MSE) approach, base temperature was estimated as 3°C for Alexander and 7°C for Morning glory. The phyllochron in Alexander grass varied from 100.1°C day leaf-1 to 142.6°C day leaf-1 as a function of maize sowing date. The plastochron in Morning glory did not vary among maize sowing dates, with an average value of 38.8°C day node-1.

CULTURAS DE SUCESSÃO AO MILHO NA DINÂMICA POPULACIONAL DE PLANTAS DANINHAS

O objetivo deste trabalho foi estudar o efeito das culturas de sucessão ao milho (aveia-preta, crotalária júncea, feijão-bravo-do-ceará, guandu, mucuna cochinchinense, girassol e milheto) na dinâmica de plantas daninhas nos sistemas convencional de preparo do solo e plantio direto no Cerrado. A matéria seca das plantas daninhas foi avaliada aos 60 dias após a semeadura das culturas de sucessão e a população de plantas daninhas aos 30 e 60 dias após a semeadura das culturas de sucessão, e aos 45 dias após a semeadura do milho. Estimou-se o banco de sementes de plantas daninhas no solo nas áreas das culturas de sucessão em julho de 2001 e de 2002. As espécies aveia-preta, feijão-bravo-do-ceará, girassol, guandu e mucuna cochinchinense, utilizadas em sucessão ao milho, reduziram a matéria seca das plantas daninhas. O plantio direto reduziu o banco de sementes de plantas daninhas no solo, porém apresentou maior taxa de emergência de plântulas no campo, em relação ao sistema convencional. O uso de culturas de sucessão aliado ao não revolvimento do solo reduz o banco de sementes de plantas daninhas no solo.

Irrigação na produção de silagem de milho e sorgo, em sucessão ao arroz de terras altas

Tendo em vista o propósito de se avaliar épocas de semeadura para maximizar a produção de arroz de terras altas e de milho e sorgo em sucessão e avaliar o retorno econômico desse sistema de produção irrigado, na região de Santa Maria, RS, conduziu-se este trabalho em área experimental do Departamento de Engenharia Rural da Universidade Federal de Santa Maria, no ano agrícola 2001/2002. Conduziu-se dois experimentos em delineamento experimental de blocos ao caso, com quatro repetições. O primeiro experimento constituiu-se de quatro datas de semeadura do arroz (18 de setembro, 4 de outubro, 19 de outubro e 5 de novembro); no segundo experimento foram utilizadas as seguintes datas de semeadura do milho e do sorgo, semeados após a colheita do arroz, em 28 de janeiro, 8 de fevereiro, 20 de fevereiro e 5 de março. As datas de semeadura do arroz ocasionaram diferenças no rendimento de grãos, apresentando a máxima eficiência técnica (5,80 Mg ha-1) na semeadura estimada de 13 de outubro. Na sucessão de culturas irrigadas de arroz de terras altas para produção de grãos e sorgo para produção de silagem, a maior receita líquida foi observada com a semeadura do arroz, na segunda quinzena de setembro.

Efeitos do manejo mecânico e químico da aveia-preta no milho em sucessão e no controle do capim-papuã

Este trabalho teve o objetivo de avaliar os efeitos do manejo mecânico e químico da palha de aveia-preta e da época de semeadura do milho após a dessecação da aveia, sobre o rendimento de grãos do milho e sobre a infestação de capim-papuã (Brachiaria plantaginea Link). No ano agrícola de (1997/98, os tratamentos constaram de dois sistemas de manejo mecânico da aveia-preta (rolada e não-rolada) e do pousio invernal (controle), da dissecação da palha de aveia-preta com dois herbicidas não-seletivos (glyphosate e paraquat) e de duas épocas de semeadura do milho após a dessecação da aveia-preta (um e 15 dias). Na estação de crescimento 1998/99, foram avaliados cinco sistemas de manejo da aveia-preta (rolada, roçada e dessecada com glyphosate, com glufosinate e com paraquat), e pousio invernal, como controle. O atraso de 15 dias na semeadura do milho após dessecação da aveia-preta aumentou o acúmulo de N, a produção de massa seca e o rendimento de grãos de milho. O rendimento de grãos de milho cultivado em sucessão à aveia-preta não foi influenciado pela forma de manejo mecânico ou pelo herbicida utilizado na dessecação da aveia-preta. A rolagem da aveia-preta foi mais eficiente em prevenir o estabelecimento de infestação de capim-papuã do que sua manutenção em pé.

Adubação nitrogenada em milho implantado em semeadura direta após aveia preta

A cultura do milho implantada em semeadura direta em sucessão a gramíneas, geralmente, apresenta deficiência inicial de nitrogênio (N). Ela é atribuída à imobilização microbiana de N durante o processo de decomposição da palha com alta razão C/N. Com a finalidade de diminuir esta deficiência, recomenda-se, para qualquer situação, a aplicação de 20 a 30kg/ha de N na semeadura. Porém, será que este manejo se aplica para todas as situações? O objetivo desta revisão é questionar a recomendação de aplicação de nitrogênio na semeadura do milho em sucessão à aveia preta e discutir a eficiência de outras três estratégias que têm sido utilizadas para diminuir a deficiência inicial de N nesta cultura. A disponibilidade de N para as culturas em sucessão é controlada pela intensidade dos processos opostos e simultâneos de imobilização e mineralização do N durante a decomposição de resíduos culturais pela população microbiana do solo. Ela é influenciada pela quantidade, tipo (razão C/N) e manejo de resíduos, temperatura do solo, regime de água/aeração, pH e pelo teor de N no solo. Assim, a resposta do milho ao manejo do N está muito relacionada ao ambiente. Outras estratégias têm sido propostas com a finalidade de diminuir a deficiência inicial de N no milho quando implantado em sucessão à aveia preta. Pode-se destacar o atraso da época de semeadura após a dessecação da aveia, a aplicação de N nos estádios iniciais de desenvolvimento da aveia e a aplicação de N no manejo da aveia, ou seja, em pré-semeadura do milho. Portanto, a recomendação do manejo do N deve resultar de uma avaliação caso a caso, evitando-se generalizações.

Manejo do nitrogênio no milho em semeadura direta em sucessão a espécies de cobertura de solo no inverno e em dois locais: I - efeito sobre a absorção de N

A permanência de restos culturais sobre a superfície do solo altera os processos de imobilização e mineralização, diminuindo a disponibilidade de nitrogênio para o milho, principalmente, em sucessão a gramíneas. O objetivo do trabalho foi o de avaliar, em dois ambientes, os efeitos de dose e época de aplicação de N no milho (0-0; 0-160; 30-130 e 60-100kg/ha, respectivamente, na semeadura e em cobertura), em sistema de semeadura direta, implantado em duas épocas após a dessecação (1 e aos 20 dias) de duas coberturas de solo no inverno (aveia preta e ervilhaca comum) e da área em pousio invernal livre de plantas daninhas, sobre a absorção de N. Foram conduzidos dois experimentos com suplementação hídrica, sendo um em Eldorado do Sul e outro em Passo Fundo, no estado do Rio Grande do Sul, no ano agrícola 1996/97. Em Eldorado do Sul, a aplicação de N na semeadura foi benéfica, pois aumentou a absorção de N em relação ao tratamento com todo o N em cobertura, independentemente da cobertura de solo no inverno testada. Em Passo Fundo, somente no estádio de 3-4 folhas, houve vantagem da aplicação de N na semeadura em relação à aplicação total em cobertura sobre a absorção de N. Nos estádios de 6-7 folhas, 10-11 folhas e de pendoamento do milho, não houve diferença entre os tratamentos com N. O atraso na época de semeadura do milho, após a dessecação em 20 dias, mostra-se tecnicamente viável, principalmente quando em sucessão à aveia preta, pois aumentou na média dos sistemas de manejo de N 54 e 75% a absorção de N, no estádio de 3-4 folhas, respectivamente em Eldorado do Sul e em Passo Fundo. A absorção de N no tecido da planta de milho em sucessão à aveia preta foi menor em Eldorado do Sul do que em Passo Fundo, em todos os estádios avaliados. O aumento na dose de N, na semeadura, de 30 para 60kg/ha de N, não se constituiu em estratégia eficiente para aumentar a absorção de N, independentemente da cobertura de solo no inverno.

A review of potato intercropping practices in western Hubei, China

Abstract The historical development of potato: maize intercropping practices is described, indicating how the desire to increase total yield, and the government decision to achieve self-sufficiency in grain production, have been accommodated. The present systems essentially consist of alternate pairs of maize rows planted one month after emergence of single or pair rows of potato. Following potato harvest, another crop is planted in its place between maize, and following the maize harvest winter wheat is frequently planted. Much yield compensation exists between potato, maize, and soybean, within this system. Research results have shown that total productivity can only be marginally increased by choice of short-season potato varieties, increase of total plant population, use of plastic mulches, and alteration of maize sowing dates, and future research concentrates on these efforts.