摘要:

The soil fertility of a biodynamic avocado plantation in Tenerife and its relation to mineral nutrition was studied and compared with similar variables investigated previously in conventional plantations. The surface soils of the biodynamic plantation showed pH, organic matter and available P, Ca, Mg and K averages significantly higher than those of the conventional plantations. As regards the foliar nutrient levels, the N, P, K, Mg and Cu averages were similar in both types of plantations, while the average foliar Ca and Mn values were significantly lower in the biodynamic avocados, although they fell within the range considered normal. On the other hand, the Zn average was significantly greater in the biodynamic plantation.

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754497

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Rumex obtusifoliusandR. crispusare easily established perennials and otherwise demonstrate life cycle strategies that enable them to reproduce vigorously and persist as seed in the soil. They are weeds when they reduce the feeding value of a sward or contaminate other crops. Many agricultural activities tend to increase the incidence of docks. Population studies consider germination, dormancy, geographical variation, seedling emergence, seed size and competitiveness. Beetles (Gastrophysaspp.) and a rust fungus (Uromyces rumicis) are amongst those organisms studied as possible agents for biological control. Cultural controls include (i) hand pulling, (ii) a series of planned rotovations and fallowing to remove existing plants and prevent seeding and (iii) land management to reduce establishment. No single method of control has been perfected and it may be that combinations of controls will prove most effective.

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754498

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A granular, calcareous seaweed soil product, “Mermin”, was applied to an established grass sward at rates of 317 and 633 kg ha−1annually for four years from October 1983 and compared with hydrated lime at the same rates and an untreated control. Soil pH rose in response to both lime and “Mermin” treatments and “Mermin” significantly increased magnesium and phosphorus levels in the soil. Earthworms were sampled on five separate occasions from March 1984 to March 1987. There was no evidence of a substantial effect of either lime or “Mermin” on worm numbers or biomass. Silage cut in May 1987 indicated that the four years of treatment had had a similarly slight effect on herbage yields. There appears to be no evidence supporting claims that “Mermin” causes increases in earthworm numbers.

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754499

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The objective of this experiment was to measure, during the seedling stage, the growth and water relations of a mixture of two winter-wheat (Triticum aestivumL.) cultivars: ‘Ponca,’ a drought-sensitive one and ‘KanKing,’ a drought-resistant one. Plants were grown in pots of soil under greenhouse conditions. Pots had one of three combinations of plants: six Ponca plants; three Ponca and three KanKing plants; or six KanKing plants. Half of the pots were watered and half were allowed to dry. Under well-watered conditions, the water potential and osmotic potential of the mixture tended to be intermediate between that of Ponca and KanKing. Under drought, Ponca and KanKing grown together had the highest water and osmotic potentials until the end of the experiment, when soil moisture was depleted. Ponca grown in monoculture and Ponca and KanKing grown together had zero turgor potential at the end of the experiment. KanKing plants grown alone were the only ones to survive the dry conditions. The results showed that when a drought-resistant cultivar was grown together with a drought-sensitive cultivar, the drought-resistant cultivar was unable to survive drought.

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754500

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Field experiments were conducted on a leached ferruginous tropical soil (Haplustalf) in the Nigerian savanna to study the effects of inoculation with four different strains ofBradyrhizobium japonicumon the agronomic performance of five promiscuously nodulating soyabean cultivars during the 1985 and 1986 wet seasons. Nodulation was significantly increased by theBradyrhizobiumstrains except IRj 2123. Inoculation had no effect on shoot dry matter yield and N content. At one of the two sites used in 1985, seed yields of inoculated treatments except strain IRj 2123 were significantly higher than the uninoculated control, and their yields were equivalent to that obtained from uninoculated plots which received 100 kg N ha−1. At the other site, only strains IRj 2114 and IRj 2133 gave higher seed yields than the uninoculated control. In 1986, although all inoculants except IRj 2123 improved yield over the control, the differences were not significant. Seed N was increased by strain IRj 2114. It is concluded that promiscuously nodulating soyabeans grown in Nigeria can benefit from inoculation with effective and adaptedBradyrhizobium japonicumstrains such as IRj 2133 and IRj 2144, especially on soils having low populations of indigenous rhizobia.

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754501

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Litter (mulch) may have potential for sustaining low-technology agriculture in at least two capacities: as a nutrient source and as weed control. This experiment discriminates between these two possible effects at a temperate site in Michigan, U.S.A. The design consisted of four factors—corn (Zea maysL.), weeds, grass-alfalfa straw mulch, and N-P-K fertilizer—each at two levels, present and absent. Measured were corn height and yield (fresh weight of cobs); weed emergence and yield (above-ground biomass); and soil levels of K, Mg, and Ca. Mulch increased corn yields evidently by suppressing weeds rather than by adding nutrients. Its effect on yield did not depend on fertilizer level. Fertilizer increased corn growth and yield; it increased weed biomass only in the absence of corn. Both mulch and fertilizer increased corn yield differentially more with weeds present than absent, mulch by suppressing weed emergence, fertilizer by benefiting corn more than weeds. Consequently, the combination of fertilizer and mulch provided excellent weed control. Generalizations about if and how much mulch might work to sustain agriculture cannot readily be inferred since timing of mulch application did not permit full decomposition and initial soil fertility was relatively high. Where more time for mulch decomposition is allowed or where soil fertility is lower, a nutrient-supplying effect of organic mulch should be more apparent.

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754502

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754503

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754504

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754505

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754506

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor