Soil nitrate N as influenced by annually undersown cover crops in spring cereals

Selostus: Aluskasvien toistuvan käytön vaikutus maan nitraattityppeen viljan viljelyssä

Physical properties of soils and soybean yields after planting cover crops

Cover crops are important for improving soil quality. However, soil properties usually have some spatial dependence. Thus, this study aimed to evaluate the effect of winter cover crops on physical properties of soil and soybean yields using thematic maps. Five winter treatments were used: black oats; intercropping 1 (forage turnips and black oats); intercropping 2 (forage turnips, black oats and common vetch); wheat; and control. Macroporosity, microporosity, total porosity, bulk density and water content of the soil from 0 - 0.1 m depths were evaluated after the winter cover crop management. Soybeans were sown over the entire area in the summer after the winter cover crop management, and the soybean yield was determined for each treatment. Maps for each treatment were created and compared to the control treatment using the relative deviation coefficient (RDC). The cover crops improved the total macroporosity of the soil in some regions of the study area. The black oats were more efficient at maintaining higher water content of the soil, and it can be used to decrease the bulk density.

Upland rice yield as affected by previous summer crop rotation (soybean or upland rice) and glyphosate management on cover crops

The appropriate chemical management of cover crops in no-tillage aims to obtain greater benefits with its employment in agricultural systems. The objective of this study was to assess upland rice yield as affected by the previous summer crop, species and desiccation timing of cover crops by glyphosate. Sown cover crops were sown (November 2007), followed by rice in half of the experimental area and soybean in the other half (November 2008). After the harvesting of these crops, the same cover crops were sown again (March 2009) and followed by upland rice in the total area (November 2009). The experiment consisted of the combination of five cover crops (fallow, Panicum maximum, Brachiaria ruziziensis, B. brizantha and Pennisetum glaucum), four desiccation timings (30, 20, 10 and 0 days before rice sowing), and two antecedents of the summer crop (rice or soybean) under no-tillage system (NTS), plus two control treatments at conventional tillage system (CTS). Cover crops significantly affect rice grain yield and its components. There is a significant tendency to highest yield when cover crop desiccation is conducted farther from the rice sowing date (from 2,577.1 kg ha-1 - desiccation at rice sowing to 3,115.30 kg ha-1 - desiccation 30 days before rice sowing). Soybean as an antecedent of summer crop allows better upland rice yield (3,754 kg ha-1) than rice as an antecedent of summer crop (2,635 kg ha-1); fallow/soybean/fallow (4,507 kg ha-1) and millet/soybean/millet (4,765 kg ha-1) rotation at no-tillage system, and incorporated fallow /soybean/ incorporated fallow (4,427 kg ha-1) at conventional tillage system allow the highest rice yield; upland rice yield is similar at no-till (3,194 kg ha-1) and till system (2,878 kg ha-1).

Corn and soybean yields as affected by cover crops and herbicide timing under no-tillage system

To achieve better results in the no-tillage system (NTS), it is important to properly manage the cover crop prior to planting by using herbicides, usually glyphosate. The effect of glyphosate on plant coverage is slow, and plants take a few days to die completely. Thus, when applying the herbicide on the same day of planting soybean or corn, cover crops are still alive and standing, causing initial shading on seedlings of the crop and delaying its establishment. Therefore, this study aimed to evaluate the effect of distinct cover crops and their timing of desiccation prior to planting soybean or corn, on crop yield and yield components. Two experiments were installed, one for soybean and another for corn. Each experiment consisted in combining three cover crops (Brachiaria brizantha, common bean or millet) chemically desiccated at two timings before planting the crop (15 or 0 days before planting) under no-tillage system (NTS). Experiments were installed in a completely randomized block design with five replications. Brachiaria brizantha produced the highest amount of biomass; common bean and millet as cover crops allowed higher soybean grain yields; herbicide application under common bean, millet and Brachiaria brizantha 15 days before planting soybean allowed higher crop grain yields; desiccation timing of common bean did not affect corn grain yield; Brachiaria brizantha should be desiccated 15 days before planting corn to allow maximum grain yield; when millet was used as a cover crop, glyphosate application at planting of corn allowed the highest grain yield.

Leguminous cover crops differentially affect maize yields in three contrasting soil types of Kakamega, Western Kenya

Maize production in smallholder farming systems in Kenya is largely limited by low soil fertility. As mineral fertilizer is expensive, green manuring using leguminous cover crops could be an alternative strategy for farmers to enhance farm productivity. However due to variability in soil type and crop management, the effects of green manure are likely to differ with farms. The objectives of this study were to evaluate Mucuna pruriens and Arachis pintoi on (i) biomass and nitrogen fixation (^15N natural abundance), (ii) soil carbon and nitrogen stocks and (iii) their effects on maize yields over two cropping seasons in Kakamega, Western Kenya. Mucuna at 6 weeks accumulated 1–1.3 Mg ha^{-1} of dry matter and 33–56 kg ha^{-1} nitrogen of which 70% was nitrogen derived from the atmosphere (Ndfa). Arachis after 12 months accumulated 2–2.7 Mg ha^{-1} of dry matter and 51–74 kg N ha^{-1} of which 52-63 % was from Ndfa. Soil carbon and nitrogen stocks at 0–15 cm depth were enhanced by 2-4 Mg C ha^{-1} and 0.3–1.0 Mg N ha^{-1} under Mucuna and Arachis fallow, irrespective of soil type. Maize yield increased by 0.5-2 Mg ha^{-1} in Mucuna and 0.5–3 Mg ha^{-1} in Arachis and the response was stronger on Nitisol than on Acrisol or Ferralsol. We concluded that leguminous cover crops seem promising in enhancing soil fertility and maize yields in Kenya, provided soil conditions and rainfall are suitable.

Factors affecting the adoption of leguminous cover crops in Nigeria and a comparison with the adoption of new crop varieties

This paper presents the results of (a) On-farm trials (eight) over a two-year period designed to test the effectiveness of leguminous cover crops in terms of increasing maize yields in Igalaland, Nigeria. (b) A survey designed to monitor the extent of, and reasons behind, adoption of the leguminous cover crop technology in subsequent years by farmers involved, to varying degrees, in the trial programme. particular emphasis was placed on comparing adoption of leguminous cover crops with that of new crop varieties released by a non-governmental organization in the same area since the mid 1980s. While the leguminous cover crop technology boosted maize grain yields by 127 to 136% above an untreated control yield of between 141 and 171 kg ha(-1), the adoption rate (number of farmers adopting) was only 18%. By way of contrast, new crop varieties had a highly variable benefit in terms of yield advantage over local varieties, with the best average increase of around 20%. Adoption rates for new crop varieties, assessed as both the number of farmers growing the varieties and the number of plots planted to the varieties, were 40% on average. The paper discusses some key factors influencing adoption of the leguminous cover crop technology, including seed availability. Implications of these results for a local non-governmental organization, the Diocesan Development Services, concerned with promoting the leguminous cover crop technology are also discussed.

A framework for designing multi-functional cover crops

Cover crops are sown to provide a number of ecosystem services including nutrient management, mitigation of diffuse pollution, improving soil structure and organic matter content, weed suppression, nitrogen fixation and provision of resources for biodiversity. Although the decision to sow a cover crop may be driven by a desire to achieve just one of these objectives, the diversity of cover crops species and mixtures available means that there is potential to combine a number of ecosystem services within the same crop and growing season. Designing multi-functional cover crops would potentially help to reconcile the often conflicting agronomic and environmental agendas and contribute to the optimal use of land. We present a framework for integrating multiple ecosystem services delivered by cover crops that aims to design a mixture of species with complementary growth habit and functionality. The optimal number and identity of species will depend on the services included in the analysis, the functional space represented by the available species pool and the community dynamics of the crop in terms of dominance and co-existence. Experience from a project that applied the framework to fertility building leys in organic systems demonstrated its potential and emphasised the importance of the initial choice of species to include in the analysis

Physical quality of an Oxisol cultivated with maize submited to cover crops in the pre-cropping period

The intensive use of land alters the distribution of the pore size which imparts consequences on the soil physical quality. The Least Limiting Water Range (LLWR) allows for the visualization of the effects of management systems upon either the improvement or the degradation of the soil physical quality. The objective of this study was to evaluate the physical quality of a Red Latosol (Oxisol) submited to cover crops in the period prior to the maize crop in a no-tillage and conventional tillage system, using porosity, soil bulk density and the LLWR as attributes. The treatments were: conventional tillage (CT) and a no-tillage system with the following cover crops: sunn hemp (Crotalaria juncea L.) (NS), pearl millet (Pennisetum americanum (L.) Leeke) (NP) and lablab (Dolichos lablab L.) (NL). The experimental design was randomized blocks in subdivided plots with six replications, with the plots being constituted by the treatments and the subplots by the layers analyzed. The no-tillage systems showed higher total porosity and soil organic matter at the 0-0.5 m layer for the CT. The CT did not differ from the NL or NS in relation to macroporosity. The NP showed the greater porosity, while CT and NS presented lower soil bulk density. No <= 10 % airing porosity was found for the treatments evaluated, and value for water content where soil aeration is critical (theta(PA)) was found above estimated water content at field capacity (theta(FC)) for all densities. Critical soil bulk density was of 1.36 and 1.43 Mg m(-3) for NP and CT, respectively. The LLWR in the no-tillage systems was limited in the upper part by the theta(FC), and in the bottom part, by the water content from which soil resistance to penetration is limiting (theta(PR)). By means of LLWR it was observed that the soil presented good physical quality.

Nitrogen Supply for Cover Crops and Effects on Peanut Grown in Succession under a No-Till System

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

Soybean root growth and yield in rotation with cover crops under chiseling and no-till

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

Cover crops and herbicide timing management on soybean yield under no-tillage system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ammonium and nitrate in soil and upland rice yield as affected by cover crops and their desiccation time

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Cotton development and yield according to nitrogen application and cover crops

Nitrogen application on the cover and the maintenance of straw, conducted by direct seeding, should meet the needs of agriculture and promote soil conservation. This study evaluates the effect of pre-sowing nitrogen application in cotton crops and cover crops by direct seeding, on the development and yield of cotton. It was conducted in the municipality of Selviria-MS during the agricultural years 2005/06, 2006/07 and 2007/08. The experimental design used was a randomized block design consisting of three cover crops (forage turnip, black oat and white oat) and four nitrogen doses (0, 30, 60 and 90 kg of N ha(-1)) in pre-sowing of cotton. In April 2006, April 2007 and April 2008, the assessments of plant development and also harvesting of the experimental plots of cotton cultivars were conducted. The results showed that after planting the cover crops, the yield and development and the heights of cotton plants increased with the use of pre-sowing N of 90 kg ha(-1), also showing that the forage turnip is a coverage plant that provides increased cotton.

Upland rice yield as affected by previous summer crop rotation (soybean or upland rice) and glyphosate management on cover crops

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)