High Soil Fertility Conditions Research Articles

Grassland plant and invertebrate species richness increases from mowing are mediated by impacts on soil chemistry

Pasture and improved grasslands are commonly managed by a combination of artificial fertilisation and biomass removal, but a deeper understanding of how management options interact over the long-term are required to improve sustainability. Studies of multi-trophic responses to these options can provide important insights for biodiversity and soil management, particularly when they cover long time periods. In this study, we provide a novel perspective on long-term experimental field studies of grassland management by examining the direct and indirect effects of N fertilisation and mowing (with biomass retention and removal) on above-ground biodiversity, below-ground soil chemistry and their interactions. Our experimental treatments were applied annually from 1994 in medium to high soil fertility conditions on a non-native pastoral farm in New Zealand, and analysis of data to 2013 show that in general, plants and soil properties did not respond to N fertiliser treatments. In response to mowing regimes, soil properties exhibited subtle, but annually varying changes mostly related to biomass retention or removal, and plant richness was consistently higher under all mowing treatments. The management regime with the greatest gains in diversity also depended on year of study. We further analysed the indirect effects of mowing treatments on plant and arthropod richness via soil properties using structural equation modelling, and found that the impact of mowing is likely to be mediated by soil chemistry changes. In particular, the direct positive impact of mowing on plant richness may be offset by changes to soil properties, depending on whether biomass is retained or removed. We suggest that management regime effects on soil chemistry may limit plant composition changes to those species able to take advantage of altered conditions. These findings suggest that management to improve grassland diversity and soil conditions should consider the abiotic history and conditions of the site.

Low Soil Nutrient Tolerance and Mineral Fertilizer Response in White Guinea Yam (Dioscorea rotundata) Genotypes.

Yam (Dioscorea spp.) is a major food security crop for millions of resource-poor farmers, particularly in West Africa. Soil mineral deficiency is the main challenge in yam production, especially with the dwindling of fallow lands for the indigenous nutrient supply. Cultivars tolerant to available low soil nutrients and responsive to added nutrient supply are viable components of an integrated soil fertility management strategy for sustainable and productive yam farming systems in West Africa. This study’s objective was to identify white Guinea yam (D. rotundata) genotypes adapted to available low soil nutrients and responsive to externally added nutrient supply. Twenty advanced breeding lines and a local variety (Amula) were evaluated under contrasting soil fertility, low to expose the crop to available low soil nutrient supply and high to assess the crop response to added mineral fertilizer (NPK) input at Ibadan, Nigeria. The genotypes expressed differential yield response to low soil fertility (LF) stress and added fertilizer input. Soil fertility susceptibility index (SFSI) ranged from 0.64 to 1.34 for tuber yield and 0.60 to 1.30 for shoot dry weight. The genotypes R034, R041, R050, R052, R060, R100, and R125 combined lower SFSI with a low rate of reduction in tuber yield were identified as tolerant to LF stress related to the soil mineral deficiency. Likewise, the genotypes R109, R119, and R131 showed high susceptibility to soil fertility level and/or fertilizer response. Genotypes R025 and R034 had the tuber yielding potential twice of that the local variety under low soil nutrient conditions. Shoot dry weight and tuber yield showed a positive correlation both under low and high soil fertility conditions (r = 0.69 and 0.75, respectively), indicating the vigor biomass may be a morphological marker for selecting genotypes of white Guinea yam for higher tuber yield. Our results highlight genotypic variation in the tolerance to low soil nutrients and mineral fertilizer response in white Guinea yam to exploit through breeding and genetic studies to develop improved genotypes for low and high input production systems in West Africa.

Optimizing N Fertilization to Improve Yield, Technological and Nutritional Quality of Tomato Grown in High Fertility Soil Conditions.

Processing tomato is the second most important worldwide cash crop, generally produced in high-input systems. However, fruit yield and quality are affected by agronomic management, particularly nitrogen (N) fertilization, whose application to indeterminate growth genotypes for canning has yet to be investigated in depth. Hence, the objective of this work was to assess the effects of different N rates (0, 50, 125, 200, 275, and 350 kg ha−1) on fruit yield and quality characteristics of processing tomato ‘San Marzano’ landrace. The results of our study showed that 125 and 200 kg of N ha−1 are the most appropriate rates in soil with high fertility, ensuring the highest values of marketable yield and brix yield. However, plants fertilized with 125 kg of N ha−1 attained higher values of N efficiency and fruit K and P concentrations than plants fertilized with 200 kg of N ha−1. Our results suggest that overdoses of N supplies negatively affected fruit yield and quality of San Marzano landrace grown in high soil fertility conditions, also reducing the agricultural sustainability. Hence, specific agronomic protocol and extension services are required to optimally manage tomato crop systems.

Integrated agronomic practice increases maize grain yield and nitrogen use efficiency under various soil fertility conditions

Crop yield potential can be increased through the use of appropriate agronomic practices. Integrated agronomic practice (IAP) is an effective way to increase maize (Zea mays L.) grain yield and nitrogen use efficiency (NUE); however, the physiological processes associated with gains in yield potential obtained from IAP, particularly the different under various soil fertility conditions, remain poorly understood. An IAP strategy including optimal planting density, split fertilizer application, and subsoiling tillage was evaluated over two growing seasons to determine whether the effects of IAP on maize yield and NUE differ under different levels of soil fertility. Compared to farmers' practices (FP), IAP increased maize grain yield in 2013 and 2014 by 25% and 28%, respectively, in low soil fertility (LSF) fields and by 36% and 37%, respectively, in high soil fertility (HSF) fields. The large yield gap was attributed mainly to greater dry matter (DM) and N accumulation with IAP than with FP owing to increased leaf area index (LAI) and DM accumulation rate, which were promoted by greater soil mineral N content (Nmin) and root length. Post-silking DM and N accumulation were also greater with IAP than with FP under HSF conditions, accounting for 60% and 43%, respectively, of total biomass and N accumulation; however, no significant differences were found for post-silking DM and N accumulation between IAP and FP under LSF conditions. Thus, the increase in grain yield with IAP was greater under HSF than under LSF. Because of greater grain yield and N uptake, IAP significantly increased N partial factor productivity, agronomic N efficiency, N recovery efficiency, and physiological efficiency of applied N compared to FP, particularly in the HSF fields. These results indicate that considerable further increases in yield and NUE can be obtained by increasing effective soil N content and maize root length to promote post-silking N and DM accumulation in maize planted at high plant density, especially in fields with low soil fertility.

GRAIN YIELD AND NITROGEN UTILIZATION IN RESPONSE TO REDUCING NITROGEN RATE IN HYBRID RICE TRANSPLANTED AS SINGLE SEEDLINGS

SUMMARYTransplanting single seedlings rather than seedlings in clumps has been increasingly attractive in hybrid rice production in China due to reduced seed requirements and higher grain yield. This study was conducted to determine grain yield and nitrogen (N) utilization in response to reductions in the N rate in hybrid rice under single-seedling transplanting. Field experiments were done in 2015 and 2016 on a moderate to high fertility soil at the Experimental Farm of Hunan Agricultural University, China. The hybrid rice cultivar Liangyoupeijiu (LYPJ) was used in 2015, and two hybrid cultivars LYPJ and Xiangliangyou 900 were used the next year. In each year, the rice plants transplanted with a single seedling per hill were grown with three N rates, including the usual N rate (150 kg ha–1) and two reduced N rates (120 and 90 kg ha–1). Grain yield, yield attributes, and N uptake and use efficiency were determined for each N rate. Significant reduction in grain yield was observed in only one of three cultivar-year combinations when N rate was reduced by 20% (from 150 to 120 kg ha–1), and the magnitude of yield reduction was only 4%. Although significant reduction in grain yield was observed in two of the three cultivar-year combinations when N rate reduced by 40% (to 90 kg ha–1), the highest yield reduction was only 7%. Yield attributes were generally changed slightly when N rate was reduced by 20%, while compensation among yield attributes and N utilization characteristics could explain why a 40% reduction in N rate did not result in substantial yield loss. Partial factor productivity of applied N (PFPN) was increased by 21–24% and 56–63% with 20% and 40% reductions in the N rate, respectively. The higher PFPN with a reduced N rate was attributed to higher recovery efficiency of applied N (REN) or to both higher REN and internal N use efficiency. Our study suggests that reducing N rate does not necessarily result in yield loss due to compensation among yield components and increased N use efficiency in hybrid rice transplanted as single seedlings under moderate to high soil fertility conditions.

Soil biota suppress positive plant diversity effects on productivity at high but not low soil fertility

SummaryPlant community productivity commonly increases with increasing plant diversity, which is explained by complementarity among plant species in resource utilization (complementarity effect), or by selection of particularly productive plant species in diverse plant communities (selection effect). Recent studies have also shown that soil biota can drive the positive plant diversity–productivity relationship by suppressing productivity more in low‐ than in high‐diversity plant communities. However, much remains unknown about whether soil fertility plays a role in determining how soil biota affect plant diversity–productivity relationships.We hypothesized that under high soil fertility conditions, negative soil biota effects dominate, which reduces plant monoculture biomass more than that of high‐diversity plant communities. Conversely, under low soil fertility conditions, we hypothesized positive soil biota effects dominate, which facilitates plant resource partitioning and enhances community‐level biomass in high‐diversity plant communities. Hence, we expected positive plant diversity–community productivity relationships under low and high soil fertility conditions but caused by different mechanisms.We tested these hypotheses using woody seedlings and set up plant assemblages with four species richness levels (one, two, four and eight species), and grew them in sterilized and unsterilized (sterilized soil + living soil inoculum) soils at two nutrient levels (low versus high fertility).We found that at high fertility negative soil biota effects dominated and suppressed plant community biomass more in high‐diversity plant communities than in monocultures, resulting in reduced complementarity effects of diverse plant communities and a non‐significant plant species richness–community biomass relationship in unsterilized soil. Whereas at low fertility soil biota had net neutral to positive effects on plant community biomass but the beneficial effects did not increase with increasing plant species richness. Instead, soil biota neutrally affected the positive plant species richness–community biomass relationship, presumably due to non‐specific effects of beneficial soil biota.Synthesis. Soil biota and soil fertility interactively determine plant species richness–community biomass relationships. Moreover, soil biota modulate the complementary resource use among plant species. These findings suggest that environmental context plays an important role in determining whether and how soil biota generate the biodiversity–productivity relationship. Future studies would benefit from revealing the mechanisms underlying the interactive effects of soil biota, soil fertility, and plant diversity on ecosystem functioning.

Effect of individual grass species and grass species mixtures on soil quality as related to root biomass and grass yield

For the purpose of feeding value, drought resistance and nitrogen utilization, other grasses (e.g. Festuca arundinacea and Dactylis glomerata) than the currently widely used perennial rye grass ( Lolium perenne) are introduced in dairy farming, either as a monoculture or in a mixture. To study the effect of these grasses on yield and soil chemical and biological quality, the three species were sown in a field experiment in monoculture and in two mixtures. Within two growing seasons, the grass species tested under high soil fertility conditions did not show significant effects on most of the tested soil biological parameters. Only for the mixture of L. perenne and D. glomerata a higher soil NO 3 − and mineral N content were most probably related to a higher bacterial activity, possibly induced by dying roots of L. perenne. This was the likely cause of the high aboveground dry matter yield of this mixture. The N-efficiencies of the monocultures of L. perenne, F. arundinacea and D. glomerata were not different when only considering the aboveground biomass. In L. perenne and F. arundinacea the total N in root biomass was higher while under D. glomerata the NO 3 − in the soil was higher. The lower fraction of mineral N to total N for L. perenne, F. arundinacea and the mixture of the two suggests that their organic matter build-up/mineralization ratio was higher than for D. glomerata. Furthermore, the mixture of L. perenne and F. arundinacea showed significantly lower soil mineral N levels than the monocultures of each. We conclude that grassland systems with a mixture of L. perenne and F. arundinacea are more sustainable than the monocultures of each, in terms of reduction of nitrogen losses and the build-up of soil organic matter. D. glomerata should only be used in a mixture in which the companion grass(es) are maintained.

Yield response of indica and tropical japonica genotypes to soil fertility conditions under rainfed uplands in northern Laos

Traditional tropical japonica genotypes ( Oryza sativa) are typically grown without fertilizer for subsistence in slash-and-burn systems by resource-poor farmers in northern Laos. Recent short fallows have reduced soil fertility and rice productivity in these systems. Genotypes adapted to a range of soil fertility conditions are needed for their food security. Rainfed experiments were conducted to identify genotypes with high yield and to examine the nature of genotype by environment (G × E) interaction for grain yield. Two improved indica genotypes and seven traditional genotypes including indica and tropical japonica groups were grown without fertilizer in ten environments over the course of 2 years. The effects of G, E and G × E interaction were significant for grain yield, yield components, plant height and days to flowering. Two improved indica genotypes (B6144F-MR-6-0-0 and IR 55423-01) and a traditional indica genotype Chao Mat out-yielded the other genotypes across the environments (2.1 t ha −1 vs. 1.6 t ha −1). Pattern analysis showed that 40.2% of the G × E sum of squares was captured by a two genotype group by two environment group summary. One environment group had higher contents of soil organic carbon and extractable P and K, and mean grain yield than another environment group. The performance of one genotype group including consisting of improved and traditional indica genotypes was more stable across two environment groups than that of another group consisting of tropical japonica genotypes, which performed well only in the high soil fertility environment group. The low grain yield of tropical japonica genotypes in the low soil fertility environment group was the result of low sink size and grain-filling percentage. In conclusion, two improved genotypes are identified for high yield in both low and high soil fertility conditions and soil organic carbon appears to be a major factor contributing the G × E interaction for grain yield as well as overall productivity.

Performance of diverse upland rice cultivars in low and high soil fertility conditions in West Africa

Traditional tropical japonica ( Oryza sativa) and Oryza glaberrima cultivars are typically grown in low-input, subsistence production systems in the uplands of West Africa by resource-poor farmers. In these systems, low soil fertility (LF), which is generally associated with lower organic carbon content, and N and P availability, is one of the major constraints to rice productivity. Thus, cultivars adapted to LF are needed for the food security of farmers, who would otherwise be solely reliant on nutrient inputs to increase productivity. This study evaluated the performance of six diverse cultivars grown in LF and high soil fertility (HF) conditions with supplemental irrigation over two seasons. Average grain yield across all cultivars in LF was 54% of that in HF (156 vs. 340 g m −2). Three improved indica rice cultivars and CG 14 ( O. glaberrima) out-yielded Morobérékan (traditional tropical japonica) and WAB450-IBP-38-HB (progeny from interspecific hybridization of tropical japonica and O. glaberrima) in LF (181 vs. 105 g m −2 on average). The high grain yield in LF was the result of large spikelet number m −2 due to superior tillering ability and high harvest index rather than biomass production. The high-yielding cultivars in LF consistently had lower leaf chlorophyll content and higher specific leaf area during the period from the early vegetative stage through the reproductive stage. Among them, two indica cultivars (B6144F-MR-6-0-0 and IR 55423-01) were also high yielding in HF. The use of improved indica cultivars adapted to LF, but also with input-responsiveness, appears to offer an attractive and economical approach to improving upland rice productivity and widening genetic diversity in this region.

Effect of cassava mosaic disease, soil fertility, plant spacing and their interactions on cassava yields in Zanzibar

Click to increase image sizeClick to decrease image sizeKeywords: CassavaCassava Mosaic DiseaseDisease SeverityPlant DensitySoil FertilityGreen ManureYield LossPembaZanzibarTanzania

Embrapa 52: nova cultivar de trigo para o Rio Grande do Sul

Para atender às demandas por cultivares de trigo (Triticum aestivum L.) com melhores níveis de rendimento, resistência a doenças e qualidade panificativa superior, foi recomendada para cultivo no Rio Grande do Sul, a partir de 1996, a cultivar EMBRAPA 52. Desenvolvida na Embrapa-Centro Nacional de Pesquisa de Trigo, apresenta ciclo precoce, estatura média e resistência ao crestamento. Pode mostrar problemas relativos ao acamamento, em condições de elevada fertilidade do solo, e à germinação na espiga, em anos chuvosos na colheita. Até a sua recomendação, apresentou comportamento fitossanitário favorável em campo, sendo suscetível em plântula a cinco raças de ferrugem-da-folha e resistente a todas as raças de ferrugem-do-colmo ocorrentes no Brasil. É moderadamente suscetível à septoriose das glumas e suscetível ao carvão. Comporta-se como resistente em campo ao oídio e ao vírus-do-mosaico-do-trigo. No período 1993-95, 'EMBRAPA 52', foi o trigo de mais alto rendimento entre todos os testados, superando em 13% as testemunhas oficiais na média geral do Estado. Pelos testes de alveografia e farinografia, foi preliminarmente classificada na classe comercial superior, sendo indicada para panificação e para fabricação de massas alimentícias e de crackers.

Soil Fertility Management Investigations on Benchmark Soils in the Humid Low Altitude Tropics of West Africa: Investigations on Egbeda Soil Series1

AbstractInformation on productivity and on suitable soil fertility management practices for sustained crop production for the major soils in the humid low altitude tropics of West Africa is still very limited. Investigations were therefore initiated on the Egbeda soil series (Oxic Paleustalf) from 1970 till 1975 in the forest zone of southern Nigeria, to determine its potential productivity and, also the effects of cultural factors on crop yield and soil properties.During 1971 and 1972 the effects of four cultural factors each at two levels (with and without fertilizer application; with and without weeding; with and without disease and insect protections; and plant population densities of 26,600 and 53,200 plants/ha) were investigated using a 24 factorial design with four replications. A maize (Zea mays L.)‐maize rotation was used. From 1973 till 1975, only the fertilizer and weeding treatments each at two levels were continued in a 22 factorial design with four replications. A maize‐sweet potato (Ipomoea batatas L.) rotation was used. Fertilizer was applied at a rate of 120 N — 66 P — 30 K in kg/ha to each maize crop. Each sweet potato crop received 40 kg N/ha. Four kg Zn/ha was applied to the 1972 main season maize crop. Each of the maize and sweet potato crops were hand weeded twice.Increasing maize plant density from 26,600 to 53,200 plants/ha significantly increased grain yield. The effect of crop protection on maize yield was inconsistent and varies with season. Fertilizer application and weeding significantly affected maize and sweet potato yields. The maize and sweet potato crops compete better with the weeds under high soil fertility conditions. Weeding appears to have more effect on sweet potato yield than fertilizer application. Maize and sweet potato yields without fertilizer application declined faster with no weeding than with weeding, partly due to nutrient competition from weeds. In the 5th cropping year without fertilizer application and weedings, maize grain yield was 450 kg/ha while sweet potato tuber yield was 4,900 kg/ha. In the same year with a weeding treatment only, maize yield was 2,500 kg/ha and sweet potato yield was 11,600 kg/ha, partly reflecting the high productivity of the soil. With fertilizer application and weeding, the maize and sweet potato yields were maintained at high levels at about 6,000 and ≥ 18,000 kg/ha respectively.Maize ear leaf composition indicated that for continuous cropping N and P appear to be the limiting nutrients during the first 6 years of cropping after clearing the secondary forest. Under low fertility conditions, sweet potato appears to be more efficient than maize in utilizing the available plant nutrients. Weeds showed higher percentage of N, P, K, Ca, and Mn than maize. The weeds also removed substantial amounts of N and particularly K, Ca, and Mg.After 4 years of application of N, P, and K, soil pH decreased from 5.80 to 5.30. The soil pH decrease was less with no weeding. Higher soil organic C content was observed with fertilizer application. Addition of 330 kg P/ha during a 4‐year period raised the level of extractable P from 11 to 70 ppm P.

Competitive growth of capeweed (Arctotheca calendula) and some annual pasture species

A comparison of the relative growth rates (RGR) of plants of capeweed (Arctotheca calendula), subterranean clover (Trifolium subterraneum) and annual ryegrass (Lolium rigidum) under high soil fertility conditions showed capeweed to have a higher RGR in the early weeks of growth, offsetting the effect of smaller seed size. However, when grown in mixed swards with the clover, under conditions of high NPK and water availability, capeweed did not readily suppress clover growth. If the capeweed and clover began growth together, clover growth was reduced by associated capeweed only after twelve weeks of growth, and then only slightly. If the capeweed was established four weeks before the clover there was a marked reduction of clover growth at the harvest eight weeks after the clover was sown. The results suggest that 'smothering' of clover by capeweed through competition for light is unlikely in grazed pastures in southern Australia.