Study on different potato continuous cropping ways on rhizosphere soil nutrients and enzyme activities

To address the problem of food security, China produced potatoes as a staple food in 2015.However, there are increasing problems with continuous cropping production methods, potato continuous cropping has been inevitable.So it is necessary to research under the different potato continuous cropping ways, potato rhizosphere soil nutrients and enzyme activities which can direct potato fertilizer and ease potato continuous cropping obstacle. A two-growing season investigation was carried out during the spring and autumn of 2014 and 2015 to determine the different ways of potato continuous cropping on the overall growth of potatoes, soil nutrients, and enzyme activities. During continuous cropping nitrogen (N) content of rhizosphere soil was reduced; available potassium (Kav) was significantly reduced(p≤5%), especially in spring and autumn continuous cropping; and total phosphorus (Ptot) was reduced during the growth stage. However, the total potassium (Ktot), available phosphorus(Pav), and organic carbon (Ctot) increased before they decreased. For rhizosphere soil enzyme activities, urease initially increased and then decreased, and was lower in continuous cropping than multiple continuous cropping; in spring of 2015, invertase was the highest with continuous cropping. Catalase and polyphenol oxidase decreased initially before increasing. Continuous cropping in spring and autumn consumed more nutrients, especially potassium (K) than in spring. Therefore, potatoes planted in both spring and autumn enhanced the problems of continuous cropping. However, multiple continuous cropping that eased rhizosphere soil nutrient absorption and effectively improves soil nutrients and enzyme activities could provide an effective method for managing the negative impacts associated with continuous cropping

Soil organic carbon dynamics of improved fallow-maize rotation systems under conventional and no-tillage in Central Zimbabwe

Fallowing increases soil organic carbon (SOC) during the fallowing phase. However, this benefit is lost quickly during the cropping phase. The objective of this study was to evaluate SOC dynamics of an improved fallow-maize rotation under no-tillage (NT) and conventional tillage (CT) from time of fallow termination, through the next two cropping seasons. The treatments studied were improved fallows of Acacia angustissima (A. angustissima) and Sesbania sesban (S. sesban), natural fallow and continuous maize. Our hypothesis is that fallowing maintained higher SOC and lower soil bulk densities through the cropping phase when compared with continuous maize system and that NT maintained higher SOC when compared with CT. Soil organic carbon was significantly greater under fallows than under continuous maize from fallow termination to the end of the second cropping season. Soil organic carbon for the 0¿5 cm depths was 11.0, 10.0, 9.4 and 6.6 g kg¿1 for A. angustissima, S. sesban, natural fallow and continuous maize, respectively at fallow termination. After two cropping seasons SOC for the same depth was 8.0, 7.0, 6.1, 5.9 g kg¿1 under CT and 9.1, 9.0, 8.0, 6.0 g kg¿1 under NT for A. angustissima, S. sesban, natural fallow and continuous maize, respectively. Total SOC stocks were also higher under fallows when compared with continuous maize at fallow termination and after two cropping seasons. Soil bulk densities were lower under fallows when compared with continuous maize during the period of study. We concluded that fallows maintained greater SOC and NT sequestered more SOC than CT. Acacia angustissima was the better tree legume fallow for SOC sequestration when compared with S. sesban or natural fallow because it maintained higher SOC and lower bulk densities after two seasons of maize cropping

Modeling impacts of farming management alternatives on CO2, CH4, and N2O emissions: A case study for water management of rice agriculture of China

Since the early 1980s, water management of rice paddies in China has changed substantially, with midseason drainage gradually replacing continuous flooding. This has provided an opportunity to estimate how a management alternative impacts greenhouse gas emissions at a large regional scale. We integrated a process-based model, DNDC, with a GIS database of paddy area, soil properties, and management factors. We simulated soil carbon sequestration (or net CO2 emission) and CH4 and N2O emissions from China\u27s rice paddies (30 million ha), based on 1990 climate and management conditions, with two water management scenarios: continuous flooding and midseason drainage. The results indicated that this change in water management has reduced aggregate CH4 emissions about 40%, or 5 Tg CH4 yr−1, roughly 5–10% of total global methane emissions from rice paddies. The mitigating effect of midseason drainage on CH4 flux was highly uneven across the country; the highest flux reductions (\u3e200 kg CH4-C ha−1 yr−1) were in Hainan, Sichuan, Hubei, and Guangdong provinces, with warmer weather and multiple-cropping rice systems. The smallest flux reductions (\u3c25 kg CH4-C ha−1 yr−1) occurred in Tianjin, Hebei, Ningxia, Liaoning, and Gansu Provinces, with relatively cool weather and single cropping systems. Shifting water management from continuous flooding to midseason drainage increased N2O emissions from Chinese rice paddies by 0.15 Tg N yr−1 (∼50% increase). This offset a large fraction of the greenhouse gas radiative forcing benefit gained by the decrease in CH4 emissions. Midseason drainage-induced N2O fluxes were high (\u3e8.0 kg N/ha) in Jilin, Liaoning, Heilongjiang, and Xinjiang provinces, where the paddy soils contained relatively high organic matter. Shifting water management from continuous flooding to midseason drainage reduced total net CO2emissions by 0.65 Tg CO2-C yr−1, which made a relatively small contribution to the net climate impact due to the low radiative potential of CO2. The change in water management had very different effects on net greenhouse gas mitigation when implemented across climatic zones, soil types, or cropping systems. Maximum CH4 reductions and minimum N2O increases were obtained when the mid-season draining was applied to rice paddies with warm weather, high soil clay content, and low soil organic matter content, for example, Sichuan, Hubei, Hunan, Guangdong, Guangxi, Anhui, and Jiangsu provinces, which have 60% of China\u27s rice paddies and produce 65% of China\u27s rice harvest

Residual effects of fallows on selected soil hydraulic properties in a kaolinitic soil subjected to conventional tillage (CT) and no tillage (NT)

Improved fallows have been used to reduce time required for soil fertility regeneration after cropping in low input agricultural systems. In semi-arid areas of Southern Africa, Acacia angustissima and Sesbania sesban are among some of the more widely used improved fallow species. However the residual effects of improved fallows on soil hydraulic properties during the cropping phase is not known. The aim of this study was to quantify the residual effects of fallows and tillage imposed at fallow termination on soil hydraulic properties (infiltration rates, hydraulic conductivity and soil porosity) during the cropping phase. Treatments evaluated were planted fallows of Acacia angustissima, Sesbania sesban and natural fallow (NF) and continuous maize as a control. Steady state infiltration rates were measured using a double ring infiltrometer and porosity was calculated as the difference between saturated infiltration rates and tension infiltration measurements on an initially saturated soil. Unsaturated hydraulic conductivity (K-o) and mean pore sizes of water conducting pores were measured using tension infiltrometer at tensions of 5 and 10 cm of water on an initially dry soil. While there was no significant difference in steady state infiltration rates from double ring infiltrometer measurements among the fallow treatments, these were significantly higher than the control. The steady state infiltration rates were 36, 67, 59 and 68 mm h(-1) for continuous maize, A. angustissima, S. sesban and NF respectively. Tillage had no significant effect on steady state infiltration rate. Pore density at 5 cm tension was significantly higher in the three fallows than in maize and varied from 285-443 m(-2) in fallows, while in continuous maize the pore density was less than 256 m(-2). At 10 cm tension pore density remained significantly higher in fallows and ranged from 4,521-8,911 m(-2) compared to 2,689-3,938 m(-2) in continuous maize. Unsaturated hydraulic conductivities at 5 cm tension were significantly higher in fallows than in continuous maize and were 0.9, 0.7, 0.8 cm and 0.5 cm h(-1) for A. angustissima, S. sesban, NF and continuous maize, respectively. However there were no significant treatment differences at 10 cm tension. Fallows improved infiltration rates, hydraulic conductivity and soil porosity relative to continuous maize cropping. Through fallowing farmers can improve the soils hydraulic properties and porosity, this is important as it affects soil water recharge, and availability for plant growt

OPTIMUM SOIL QUALITY ATTRIBUTE LEVELS AND VALUES

We develop a dynamic optimal cropping systems model for the northern Great Plains, taking into account the impact of the system on soil quality attributes organic and inorganic carbon. Continuous wheat and direct planting is the most profitable system under most economic conditions. This system has low soil erosion and results in high soil quality.Land Economics/Use,

Vegetable quality in a conventional and three organic cropping systems

Differences in nutrient availability and methods of pest management may affect crop growth and product quality. The question is if conventional and organic cropping systems, which differ clearly in strategies for nutrient and pest management, influence the harvest and sensory quality of the products? Lettuce and onion were grown in a conventional and three organic vegetable cropping systems with different levels of external inputs and use of cover- and inter-crops for nutrient re-cycling and natural pest management in the period of 2007-2009 (VegQure project). The crop rotation consisted of 8 fields of vegetables and cereals. Onion was grown after a year of oat and iceberg lettuce after winter rye. There were 3 replicates of each cropping system each year. Sensory analysis of samples of iceberg lettuce was performed as quantitative descriptive analysis by a trained sensory panel of 10 assessors. A sensory profile of 9 attributes was evaluated on a 15-cm non-structured continuous scale. Harvest and sensory quality were not affected by the clear differences in nutrient and pest management between the four cropping systems

Greenhouse Gas Mitigation on Diversified Farms

Agriculture can potentially contribute to Canada meeting its commitment to reduce net greenhouse gas (GHG) emissions under the Kyoto protocol. A representative crop - livestock feeding farm on the Canadian prairies is used to estimate the cost of net GHG abatement, taking into account CO2 equivalent emissions and carbon sequestration. Optimal cropping systems use direct seeding and continuous cropping, production systems that have lower net GHG emissions. Livestock feeding uses rations with high energy concentration (grain based) because they are more profitable and also produce less methane per animal than forage based diets. Reducing tillage is the least costly means of lowering net emissions ($20/t CO2 eq.), followed by reducing cattle feeding ($32/t CO2 eq.). If emission reductions are high or cattle numbers can not be reduced, cropping is altered to use very little nitrogen fertilizer ($272-567/t CO2 eq.), and cattle feeding is switched to a higher forage diet (up to$1500/t CO2 eq.). The high forage diet has lower emissions per capacity animal, but only because one-half the number of animals can be finished with the same facility capacity. A regional analyses of aggregate emissions will need to incorporate the heterogeneity of farms and soil carbon levels that exist.Environmental Economics and Policy,

Short-term effect of soil disturbance by mechanical weeding on plant available nutrients in an organic vs conventional rotations experiment

The question whether soil disturbance from mechanical weeding in organic systems affects nutrient release from organic matter in compost-amended soil was examined in a long-term organic-versus-conventional rotational cropping system experiment over three years. The experimental design included continuous snap beans, and a fully phased snap beans/fall rye crop rotation sequence. Treatments were combinations of yearly applied fertiliser (synthetic fertiliser, 1× compost, 3× compost) and weed control (herbicide, mechanical weeding). The 1× compost rate was calculated to deliver the equivalent of 50 kg N ha-1: equal to the rate ofN in the synthetic fertiliser treatments. Ion exchange membranes were buried for 24 hours following mechanical weeding in bean plots. Adsorbed ions were then eluted and quantified. Available ammonium-nitrogen was not affected byweeding treatment, but nitrate-nitrogen was consistently less in mechanically weeded plots than in plots treated with herbicide. Principal component analysis of NH4-N, NO3-N, P, K, Ca and Mg availabilities showed distinct groupings of treatments according to fertility treatment rather than weeding treatment. The effect of cropping sequence on available nutrients was pronounced (P ≤ 0.001) only in plots amended with synthetic fertilisers

Functional Biodiversity

Modern conventional agriculture is characterized by monocultures. These are less productive in terms of biomass than natural plant communities, which are usually complex mixtures of species and varieties, and they also require more inputs. A central question for organic agriculture is therefore how far we can move from monocultural to polycultural systems in order to benefit from this biodiversity without loss of yield. Rotations are one way of increasing biodiversity, but other components of the EFRC research programme are relevant: breeding programmes for wheat and kale aimed at producing crop populations rather than pure lines; variety and species mixtures, especially for cereals; intercropping legumes with a vegetable rotation (companion cropping) or cereals (bi-cropping), in order to bring the fertility-building and cropping phases of the rotation into the same part of the sequence; a biodiversity project looking at the farmed and non-farmed areas of organic and conventional farms; N, P and K budgeting as a means of designing rotations and intercropping systems; semiochemicals: the natural signalling processes between crops, pests and predators. The best illustration of functional biodiversity is perhaps in the agroforestry demonstration plots, where trees, cropping and livestock are combined

Our Heritage, the Soil

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