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1.
Protected cultivation, mainly represented by plastic-film mulching, has greatly improved crop production worldwide since the 1950s. However, despite its widespread use in tropical USA, Europe and China, its use in sub-Saharan Africa is not widespread. A field experiment was conducted using cocoyam (Colocasia esculenta L. Schott) to evaluate the effects of two tillage systems (tilled and no-till) and plastic-film mulch (black and clear plastic-film mulch) on soil properties and cocoyam growth and yield in 2003 and 2004 planting seasons on a Typic paleudult in southeastern Nigeria. The experiment comprised six treatments and was laid out in the field using randomized complete block design replicated three times. Results showed that 70–80% of the corms emerged 7–8 days (21 days after planting [DAP]) earlier in both tilled and no-till plastic-film mulched plots when compared to the unmulched plots. At later stages of crop development, the plants in the tilled black plastic-film mulched plots were taller by 61–67% than those in the unmulched no-till plots, which had the lowest plant height (27–30 cm). At 98 DAP, there were no significant treatment differences in leaf area index (LAI) between tilled and no-till mulched plots with LAI of 15.5–19.8. However, LAI was reduced in both unmulched plots by 35–54% when compared to the mulched plots. On the average soil temperature was higher in plastic-film mulched plots than that under plots without mulch by about 2 °C. Results show significantly lower soil bulk density (between 1.10 and 1.26 Mg m−3) in both tilled clear and black plastic-film mulched plots when compared to the corresponding no-till clear or black plastic-film mulched plots (1.40–1.45 Mg m−3). For the two seasons studied volumetric water content (VWC) in tilled black plastic-film mulched plots were significantly higher than VWC in other mulched plots by between 10 and 38% in 2003 and between 17 and 30% in 2004. At harvest (270 DAP) the highest corm yield was obtained in tilled black plastic mulched plots (29.1 Mg ha−1). This was higher (P = 0.05) than yields obtained in no-till, no mulch plots by 72%. Yields were also higher in tilled black plastic mulched plots when compared to tilled clear plastic mulched plots, no-till black plastic mulched plots and no-till clear plastic mulched plots by 29, 47 and 59%, respectively. These findings suggest that plastic mulched plots provide a better soil environment for cocoyam than unmulched plots and that tilled mulched plots especially tilled black plastic mulched plots provide superior edaphic environment for cocoyam when compared to other treatments used.  相似文献   

2.
We examined the effects of various tillage intensities: no-tillage (NT), minimum tillage with chisel plow (MT), conventional tillage with mouldboard plow (CT), and zone-tillage subsoiling with a paraplow (ZT) applied in alternate years in rotation with NT, on the topsoil profile distribution (0–30 cm) of pH, soil organic carbon (SOC), organic N and available nutrients on a semi-arid soil from Central Spain. The equivalent depth approach was used to compare SOC, N and nutrient stocks in the various tillage treatments. Measurements made at the end of 5 years showed that in the 0–30 cm depth, SOC and N had increased under NT and ZT compared with MT and CT. Most dramatic changes occurred within the 0–5 cm depth where plots under NT and ZT had respectively 7.0 Mg ha−1 and 6.2 Mg ha−1 more SOC and 0.5 Mg ha−1 and 0.3 Mg ha−1 more N than under MT or CT. No-tillage and ZT plots, however, exhibited strong vertical gradients of SOC and N with concentrations decreasing from 0–5 to 20–30 cm. In the 0–20 cm layer, higher concentrations of P and K under NT and ZT than under MT or CT were also found. Soil pH under NT and ZT was 0.3 units lower than under MT or CT at a depth of 0–5 cm. This acidifying effect was restricted at the surface layer and in the 20–30 cm interval, pH values under NT and ZT were higher than in MT and CT plots. These results suggest that in the soil studied, ZT in rotation with NT maintain most advantages associated with NT, and present a definite potential for use as a partial-width rotational tillage practice.  相似文献   

3.
A study was carried out on a previously eroded Oxic Paleustalf in Ibadan, southwestern Nigeria to determine the extent of soil degradation under mound tillage with some herbaceous legumes and residue management methods. A series of factorial experiments was carried out on 12 existing runoff plots. The study commenced in 1996 after a 5-year natural fallow. Mound tillage was introduced in 1997 till 1999. The legumes – Vigna unguiculata (cowpea), Mucuna pruriens and Pueraria phaseoloides – were intercropped with maize in 1996 and 1998 while yam was planted alone in 1997 and 1999. This paper covers 1997–1999. At the end of each year, residues were either burned or mulched on respective plots. Soil loss, runoff, variations in mound height, bulk density, soil water retention and sorptivity were measured. Cumulative runoff was similar among interactions of legume and residue management in 1997 (57–151 mm) and 1999 (206–397 mm). However, in 1998, cumulative runoff of 95 mm observed for Mucuna-burned residue was significantly greater than the 46 mm observed for cowpea-burned residue and the 39–51 mm observed for mulched residues of cowpea, Mucuna and Pueraria. Cumulative soil loss of 7.6 Mg ha−1 observed for Mucuna-burned residue in 1997 was significantly greater than those for Pueraria-mulched (0.9 Mg ha−1) and Mucuna-mulched (1.4 Mg ha−1) residues whereas in 1999 it was similar to soil loss from cowpea treatments and Pueraria-burned residue (2.3–5.3 Mg ha−1). There were no significant differences in soil loss in 1998 (1–3.2 Mg ha−1) whereas Mucuna-burned residue had a greater soil loss (28.6 Mg ha−1) than mulched cowpea (6.9 Mg ha−1) and Pueraria (5.4 Mg ha−1). Mound heights (23 cm average) decreased non-linearly with cumulative rainfall. A cumulative rainfall of 500 mm removed 0.3–2.3 cm of soil from mounds in 1997, 3.5–6.9 cm in 1998 and 2.3–4.6 cm in 1999, indicating that (detached but less transported) soil from mounds was far higher than observed soil loss in each year. Soil water retention was improved at potentials ranging from −1 to −1500 kPa by Mucuna-mulched residue compared to the various burned-residue treatments. Also, mound sorptivity at −1 cm water head (14.3 cm h−1/2) was higher than furrow sorptivity (8.5 cm h−1/2), indicating differences in hydraulic characteristics between mound and furrow. Pueraria-mulched residues for mounds had the highest sorptivity of 17.24 cm h−1/2, whereas the least value of 6.96 cm h−1/2 was observed in furrow of Mucuna-burned residue. Pueraria phas eoloides was considered the best option for soil conservation on the previously eroded soil, cultivated with mound tillage.  相似文献   

4.
Soil organic matter (SOM) contributes to the productivity and physical properties of soils. Although crop productivity is sustained mainly through the application of organic manure in the Indian Himalayas, no information is available on the effects of long-term manure addition along with mineral fertilizers on C sequestration and the contribution of total C input towards soil organic C (SOC) storage. We analyzed results of a long-term experiment, initiated in 1973 on a sandy loam soil under rainfed conditions to determine the influence of different combinations of NPK fertilizer and fertilizer + farmyard manure (FYM) at 10 Mg ha−1 on SOC content and its changes in the 0–45 cm soil depth. Concentration of SOC increased 40 and 70% in the NPK + FYM-treated plots as compared to NPK (43.1 Mg C ha−1) and unfertilized control plots (35.5 Mg C ha−1), respectively. Average annual contribution of C input from soybean (Glycine max (L.) Merr.) was 29% and that from wheat (Triticum aestivum L. Emend. Flori and Paol) was 24% of the harvestable above-ground biomass yield. Annual gross C input and annual rate of total SOC enrichment were 4852 and 900 kg C ha−1, respectively, for the plots under NPK + FYM. It was estimated that 19% of the gross C input contributed towards the increase in SOC content. C loss from native SOM during 30 years averaged 61 kg C ha−1 yr−1. The estimated quantity of biomass C required to maintain equilibrium SOM content was 321 kg ha−1 yr−1. The total annual C input by the soybean–wheat rotation in the plots under unfertilized control was 890 kg ha−1 yr−1. Thus, increase in SOC concentration under long-term (30 years) rainfed soybean–wheat cropping was due to the fact that annual C input by the system was higher than the required amount to maintaining equilibrium SOM content.  相似文献   

5.
Soil organic carbon (SOC) has an important role in improving soil quality and sustainable production. A long-term fertilization study was conducted to investigate changes in SOC and its relation to soil physical properties in a rice paddy soil. The paddy soils analyzed were subjected to different fertilization practices: continuous application of inorganic fertilizers (NPK, N–P–K = 120–34.9–66.7 kg ha−1 yr−1 during 1967–1972 and 150–43.7–83.3 kg ha−1 yr−1 from 1973 to 2007), straw based compost (Compost, 10 Mg ha−1 yr−1), a combination of NPK + Compost, and no fertilization (control). Soil physical properties were investigated at rice harvesting stage in the 41st year for analyzing the relationship with SOC fraction. Continuous compost application increased the total SOC concentration in plough layers and improved soil physical properties. In contrast, inorganic or no fertilization markedly decreased SOC concentration resulting to a deterioration of soil physical health. Most of the SOC was the organo-mineral fraction (<0.053 mm size), accounting for over 70% of total SOC. Macro-aggregate SOC fraction (2–0.25 mm size), which is used as an indicator of soil quality rather than total SOC, covered 8–17% of total SOC. These two SOC fractions accumulated with the same tendency as the total SOC changes. Comparatively, micro-aggregate SOC (0.25–0.053 mm size), which has high correlation with physical properties, significantly decreased with time, irrespective of the inorganic fertilizers or compost application, but the mechanism of decrease is not clear. Conclusively, compost increased total SOC content and effective SOC fraction, thereby improving soil physical properties and sustaining production.  相似文献   

6.
Soil C and N contents play a crucial role in sustaining soil quality and environmental quality. The conversion of annually cultivated land to forage grasses has potential to increase C and N sequestration. The objective of this study was to investigate the short-term changes in soil organic C (SOC) and N pools after annual crops were converted to alfalfa (Medicago sativa L. Algonguin) forage for 4 years. Soil from 24 sets of paired sites, alfalfa field versus adjacent cropland, were sampled at depths of 0–5, 5–10 and 10–20 cm. Total soil organic C and N, particulate organic matter (POM) C and N were determined. Organic C, total N, POM-C, and POM-N contents in the 0–5 cm layer were significantly greater in alfalfa field than in adjacent cropland. However, when the entire 0–20 cm layer was considered, there were significant differences in SOC, POM-C and POM-N but not in total N between alfalfa and crop soils. Also, greater differences in POM-C and POM-N were between the two land-use treatments than in SOC and total N were found. Across all sites, SOC and total N in the 0–20 cm profile averaged 22.1 Mg C ha−1 and 2.3 Mg N ha−1 for alfalfa soils, and 19.8 Mg C ha−1and 2.2 Mg N ha−1 for adjacent crop soils. Estimated C sequestration rate (0–20 cm) following crops to alfalfa conversions averaged 0.57 Mg C ha−1 year−1. Sandy soils have more significant C accumulation than silt loam soils after conversion. The result of this suggests that the soils studied have great C sequestration potential, and the conversion of crops to alfalfa should be widely used to sequester C and improve soil quality in this region.  相似文献   

7.
Integrated crop–livestock management systems (ICLS) have been increasingly recommended in Brazilian agroecosystems. However, knowledge of their effect on soil organic carbon (SOC) and total nitrogen (TN) concentrations and stocks is still limited. The study was undertaken to evaluate the effects of ICLS under two tillage and fertilization regimes on SOC and TN concentrations and stocks in the 0–30 cm soil layer, in comparison with continuous crops or pasture. The following soil management systems were studied: continuous pasture; continuous crop; 4 years’ crop followed by 4 years’ pasture and vice-versa. The adjacent native Cerrado area was used as a control. Under the rotation and continuous crop systems there were two levels of soil tillage (conventional and no-tillage) and fertility (maintenance and corrective fertility). The stock calculations were done using the equivalent soil mass approach. The land use systems had a significant effect on the concentrations of SOC and TN in the soil, but no effect was observed for the soil tillage and fertilizer regimes. For these two latter, some significant discrepancies appeared in the distribution of SOC and TN concentrations in the 0–30 cm layer. Carbon storage was 60.87 Mg ha−1 under Cerrado, and ranged from 52.21 Mg ha−1 under the ICLS rotation to 59.89 Mg ha−1 with continuous cropping. The decrease in SOC stocks was approximately 8.5 and 7.5 Mg ha−1, or 14 and 12%, for continuous pasture and ICLS respectively. No-tillage for 10 years after the conversion of conventional tillage to no-tillage under the continuous crop system, and 13 years of conventional tillage in continuous cropping did not result in significant changes in SOC stocks. The SOC and TN stocks in surface layers, using the equivalent soil mass approach rather than the equivalent depth, stress the differences induced by the calculation method. As soil compaction is the principal feature of variability of stocks determinations, the thickness should be avoid in these types of studies.  相似文献   

8.
Enhancement of soil organic carbon (SOC) stocks through mulching has been proposed, and although this practice can alter several soil properties, its impact on the temporal variability of carbon dioxide (CO2) emission from soils has not been widely investigated. To that end, we monitored CO2 fluxes from a central Ohio Luvisol (fine, mixed, mesic Aeric Ochraqualf) amended with wheat (Triticum aestivum L.) straw applied at rates of 0 (M0), 8 (M8) and 16 (M16) Mg dry matter ha−1 per year and supplemented with fertilizer (244 kg N ha−1 per year) or without. The experimental design was a randomized complete block design with three replications. The intensity of CO2 emission was higher in the late winter (mean: 2.79 g CO2-C m−2 per day) and summer seasons (2.45 g CO2-C m−2 per day) and lowest in the autumn (1.34 g CO2-C m−2 per day). While no significant effect of N fertilization on CO2 emission was detected, soil mulching had a significant effect on the seasonal variation of CO2 fluxes. The percentage of annual CO2 emitted during the winter and spring was similar across treatments (17–22%); however, 43% of the annual CO2 loss in the M0 plots occurred during the summer as opposed to 26% in the mulch treatments. A close relationship (F=0.47X+4.45, R2=0.97, P<0.001) was found between annual CO2 flux (F, Mg CO2-C ha−1) and residue-C input (X, Mg C ha−1). Litter and undecomposed residue amounted to 0.32 and 0.67 Mg C ha−1 per year in the M8 and M16 plots, respectively. After 4 years of straw application, SOC stocks (0–10 cm) were 19.6, 25.6 and 26.5 Mg C ha−1 in the M0, M8 and M16 treatments, respectively. The results show that soil mulching has beneficial effect on SOC sequestration and strongly influence the temporal pattern of CO2 emission from soils.  相似文献   

9.
Soil porosity and organic matter content influence the hydrology, thermal status and productivity of agricultural soils. Shape, size and continuity of soil pores are determined by tillage practices. Thus appropriate tillage and mulch management can conserve residual soil moisture during the post rainy season. This can play a key role in enhancing productivity under the rainfed ecosystem of subhumid region in eastern India. A field study was carried out on a fine loamy soil from 1993–1994 to 1995–1996. Two tillage treatments were conventional ploughing (150 mm depth) and shallow ploughing (90 mm) depth. Each tillage practice was tested with three mulch management viz., no mulch, soil dust mulch and rice (Oryza sativa L.) straw mulch. Soil organic carbon, bulk density, moisture retentivity, soil temperature with productivity and water use pattern of barley (Hordium vulgare L.) were measured.Reduction in ploughing depth resulted in nominal increase in profile (0.0–1.2 m) moisture status, yield, and soil thermal status at 14:00 and water use efficiency (WUE). However, it decreased the magnitude of soil temperature in the morning (07:00). Straw mulch conserved 19–21 mm of moisture in the profile (1.2 m) over the unmulched condition. Both soil dust and rice straw mulching elevated soil thermal status at 07:00 as compared to unmulched condition, but this trend was reversed at 14:00. Straw mulching significantly increased grain yield and WUE over soil dust mulch and unmulched condition. Impact of straw mulch was more pronounced under shallow ploughing depth. Shallow tillage with rice straw mulching is recommended to the farmers to obtain higher level of yield and water use efficiency.  相似文献   

10.
Many previous studies have focused on soil gravel concentrations and their effect on crop yields in agricultural systems. The extent of carbon and nitrogen sequestration in soils under steppe systems in relation to surface gravel mulch remains largely unexplored. This study investigated the effects of gravel mulches on soil organic carbon and total nitrogen stocks in the arid and windy regions of the Tibetan Plateau. Surface gravel mulches provide a more favorable environment for soil carbon and nitrogen stocks than do non-mulched sites. Soil organic carbon and total nitrogen stocks were highest (46.9 Mg ha− 1 SOC and 2.8 Mg ha− 1 TN) in the medium gravel mulch sites with ~ 40-50% gravel, and lowest (29.5 Mg ha− 1 SOC and 1.4 Mg ha− 1 TN) in no gravel mulch sites. Analysis of aggregate size fractions indicated that the vast majority of SOC was present in microaggregate fractions throughout the top 30 cm of soil. Considering the low level of soil disturbance in the study area, the carbon contained in the macroaggregate fraction might become stabilized in the soil. Gravel mulches above the soil surface have an important bearing on soil carbon sequestration as they control wind erosion, decrease soil surface evaporation and change soil physical behavior in the arid and semiarid regions.  相似文献   

11.
Distillery effluent, a foul smelling, dark coloured by-product of distillery industries, is usually applied as irrigation water or as an amendment to arable land in some areas which are in the vicinity of the distillery industries. A field experiment on soybean–wheat system was conducted for 3 consecutive years in a Vertisol of central India to evaluate the effect of distillery effluent (DE) as an amendment on soil properties and crop productivity. The treatments were control (no fertilizer or manure or DE, T1), 100% NPK + FYM @ 4 Mg ha−1 to soybean (T2) and four graded levels of DE, viz.: 2.5 cm DE to soybean and wheat on residual nutrition (T3), 2.5 cm DE to soybean and 1.25 cm to wheat (T4), 5 cm DE to soybean and wheat on residual nutrition (T5), 5 cm DE to soybean and 2.5 cm to wheat (T6). The organic carbon, microbial biomass carbon and electrical conductivity (EC) of the surface (0–10 cm) soil increased significantly with application of DE compared to T1 and T2, but the soil pH was not affected. The EC increased from 0.47 dS m−1 and 0.58 dS m−1, respectively, in T1 and T2 to 1.52 dS m−1 in T6, where highest dose of DE was applied. This indicated a slight build-up of salinity with DE application. The application of DE showed a significant improvement in the physical properties of the soil. The mean weight diameter (MWD), saturated hydraulic conductivity, water retention at field capacity and available water content were significantly (P < 0.05) higher, while bulk density (BD) and penetration resistance of the surface soil were significantly lower (P < 0.05) in all DE treated plots except in T3 than those in T1 and T2. The fractions of WSA of more than 1 mm diameter in T6, T5 and T4 were, respectively, 141%, 107% and 116% more than the control. The MWD showed a positive linear relationship with the organic carbon (r = 0.84**) and microbial biomass carbon (r = 0.90**) of the soil. A significant (P < 0.01) negative linear relationship (r = 0.70**) was found between soil organic carbon and BD. Except T3, all the DE treated plots recorded significantly higher total and microporosity of the soil than control. Water retention at permanent wilting point and macroporosity of the soil were not affected by treatment. The seed yield of soybean in all the DE treatments was similar with T2 (1.86 Mg ha−1) but significantly more than control (1.28 Mg ha−1). The DE application levels have not affected the seed yield of soybean. In wheat highest grain yield was recorded in T2 (3.47 Mg ha−1), which was similar with T4 (3.16 Mg ha−1), T5 (3.22 Mg ha−1) and T6 (3.46 Mg ha−1). DE application up to T4 level was found suitable from productivity, salinity and sustainability point of view. The study showed that judicious application of DE as an amendment to the agricultural field could be considered as a viable option for safe disposal of this industrial waste.  相似文献   

12.
Time of mulching can influence the growth environment and performance of white yam (Dioscorea rotundata Poir). An on-farm trial was conducted during the 1988–1989 and 1989–1990 seasons (October–August) in Nigeria to determine the effect of time of mulching (October–February) on the hydrothermal regime and emergence, growth and tuber yield of white yam. Application of 12.5 mg ha−1 of dry Eupatorium odoratum L. (Syn. Chromolaena odorata L.) mulch on top of the mounds significantly improved soil moisture content of the 15 cm surface layer by 50–120 g kg−1 and decreased the maximum soil temperature by 2–7°C at 15 cm depth in the early growing season (March–April). The emergence and development of yam seedlings were significantly lower in unmulched plots than in mulch-treated plots. Mulching significantly increased tuber yield by about 10–15 mg ha−1 season−1. Plots mulched in October–December were more moist by 20–60 g kg−1 and cooler by 1–3°C, and had 27–44% greater emergence than those mulched in January or February. The number of leaves per plant, vine diameter and leaf area index were also significantly greater in plots mulched in October–December than plots mulched in January or February. Consequently, shoot dry weight was about 28–36% greater in yam mulched in October–December than in yam mulched in February. However, the time of mulching had no effect on soil moisture of the surface layer at the beginning of the rainy season (April), on yam emergence in May and on tuber yield and yield components. Although time of mulching did not significantly affect tuber yield, the increase (10–15%) in the tuber yield of yam mulched in December–February compared to the yam mulched in October or November was considerable. It was concluded that yam planted in October, just before the rain stops, can be mulched in January or February without detrimental effect on emergence, growth and tuber yield.  相似文献   

13.
Organic matter influences soil structure and compactibility by binding soil mineral particles, reducing aggregate wettability, and influencing the mechanical strength of soil aggregates, which is the measure of coherence of inter-particle bonds. This work was carried out to examine how differences in water-stable aggregates influence the distribution of soil organic carbon and soil organic nitrogen under two tillage techniques [minimum tillage (only planting holes were opened) and conventional tillage (raised beds, 30 cm high, prepared manually with traditional hoes)] in soils of a Fluvisol in Owerri, southeastern Nigeria. Three pedons were dug and studied for each of the tillage technique along a soil sequence. Soil organic carbon and soil organic nitrogen distribution in whole soil and in water-stable aggregates under minimum tillage and conventional tillage were determined for the soils. Soil organic carbon contents in water-stable aggregates (WSA) of the pedons varied according to method of tillage. The highest mean values of soil organic carbon were obtained from minimum tillage and in water-stable aggregates 4.75–2.00 mm (16.03 Mg C ha−1), 1.00–0.50 mm (14.06 Mg C ha−1) and water-stable aggregates 2.00–1.00 mm (13.99 Mg C ha−1) whereas under conventional tillage, water-stable aggregates 1.00–0.50 mm with soil organic carbon of 24.6 Mg C ha−1 had the highest soil organic carbon content. Soil organic carbon correlated significantly with mean weight diameter (r = 0.48; P = 0.05; n = 15), water-stable aggregates 4.75–2.00 mm (r = 0.73; P = 0.05; n = 15), water-stable aggregates 2.00–1.00 mm (r = 0.55; P = 0.05, n = 15), water-stable aggregates 1.00–0.50 mm (r = 0.44; P = 0.05; n = 15) whereas no relationship was found between soil organic carbon and water-stable aggregates 0.50–0.25 mm (r = 0.15; P = 0.05; n = 15) and water-stable aggregates <0.25 mm (r = 0.17; P = 0.05; n = 15) in soils under minimum tillage. There was a significant correlation (r = 0.45–0.58; P = 0.05; n = 14) between all water-stable aggregates classes studied and soil organic carbon in soils under conventional tillage. Mean values of soil organic nitrogen were higher in soils under minimum tillage with 4.75–2.00 mm and 2.00–1.00 mm aggregate classes having 1.64 Mg N ha−1 and 1.57 Mg N ha−1 soil organic nitrogen when compared to 1.01 Mg N ha−1 and 1.00 Mg N ha−1 in conventionally tilled soils of the same aggregate classes, respectively. Larger water-stable aggregate classes (4.75–2.00; 2.00–1.00) had slightly more soil organic nitrogen (22–26%) than smaller aggregate classes (1.00–0.50; 0.50–0.25; >0.25) with 14–24% soil organic nitrogen in minimum tilled soils. In soils under conventional tillage, 1.00–0.50 mm, 0.50–0.25 mm and <0.25 mm aggregate classes contributed more soil organic nitrogen (19.66–22.40%) to the soil whereas larger water-stable aggregate classes contributed 19.22% soil organic nitrogen. The proportion of soil organic carbon and total nitrogen retained in soils with higher percentage of water-stable aggregates are less likely to be lost through soil and wind erosion. The higher values of SOC in the whole soil and WSA classes less than 2.00 mm are indications of positive influence of SOC on the stability of these peds.  相似文献   

14.
This study aimed at investigating the effects of agricultural exploitation on desert soil organic C, N and P, and soil aggregation. Four land uses were assessed: (1) 5-year wheat (Triticum aestivum L.)/barley (Hordeum vulgare L.) + 5-year maize (Zea mays L.); (2) 5-year wheat/barley + 5-year alfalfa (Medicago sativa L.); (3) 6-year wheat/barley + 4-year acacia (Robinia pseudoacacia L.) and (4) uncultivated desert soil. The desert soil contained total organic C (TOC) of 3.1, 3.7 and 4.2 g kg−1 and particulate organic C (POC) of 0.6, 0.7 and 0.8 g kg−1 at 0–10, 10–20 and 20–30 cm depths, respectively. The soil TOC concentration was increased by 32–68% under wheat–maize rotation and by 27–136% under wheat–acacia at 0–20 cm depth, and by 48% under wheat–alfalfa only at 0–10 cm depth. This contrasted with an increase in the soil POC concentration by 143–167% at depth 0–20 cm under wheat–maize and by 217%, 550% at depth 0–10 cm under wheat–alfalfa and wheat–acacia, respectively. The desert soil had 13 Mg ha−1 TOC stock and 2 Mg ha−1 POC stock at depth 0–30 cm, whereas crop rotations increased the soil TOC stock by 30–65% and POC stock by 200–350%. Over the 10-year period, the rates of TOC accumulation were 0.6, 0.3, 0.8 Mg ha−1 year−1 and the rates of POC accumulation were 0.4, 0.4 and 0.7 Mg ha−1 year−1 under wheat–maize, wheat–alfalfa and wheat–acacia rotations, respectively. At 0–30 cm depth, total soil N was increased by 61–64% under wheat–maize and wheat–acacia, but total soil P was reduced by 38% under wheat–alfalfa. A significant improvement in clay stability but not in aggregate water-stability was observed in cultivated soils. The results showed a significant increase in soil organic C pool but unimproved macro-aggregation of the desert soil after 10 years of cultivation.  相似文献   

15.
High population pressure in the central highlands of Kenya has led to continuous cultivation of land with minimal additional inputs leading to soil nutrient depletion. Research work has reported positive results from use of manure and biomass from Tithonia, Calliandra, Leucaena, Mucuna and Crotolaria for soil fertility replenishment. An experimental field was set up in Chuka Division to test different soil nutrient replenishment treatments. The experimental design was randomised complete block with 14 treatments replicated three times. At the beginning and end of the experiment, soil was sampled at 0–15 cm depth and analysed for pH, Ca, Mg, K, C, N and P. End of the 2000/2001 short rains (SR) season and 2001 long rains (LR) season, soil samples were taken at 0–30, 30–100 and 100–150 cm for nitrate and ammonium analysis. All the treatments received an equivalent of 60 kg N ha−1, except herbaceous legume treatments, where N was determined by the amount of the biomass harvested and incorporated in soil and control treatment received no inputs. Results indicate soil fertility increased slightly in all treatments (except control) over the 2-year study period. Average maize grain yield across the treatments was 1.1, 5.4, 3.5 and 4.0 Mg ha−1 during the 2000 LR, 2000/2001 SR, 2001 LR and 2001/2002 SR, respectively. The reduced yield in 2000 LR and 2001 LR are attributed to poor rainfall distribution during the two seasons. On average, Tithonia with half recommended rate of inorganic fertilizer recorded the highest (4.8 Mg ha−1) maize yield followed by sole Tithonia (4.7 Mg ha−1). Highest average concentration (144.8 and 115.5 kg N ha−1) of mineral N was recorded at the 30–100 cm soil depth at the end of both 2000/2001 SR and LR, respectively. The lowest average concentration (67.1 kg N ha−1) was recorded in the 100–150 cm soil depth in both seasons, while during the 2001 LR, the 0–30 cm soil depth recorded the lowest concentration (52.3 kg N ha−1). The residual mineral N in the 100–150 cm soil depth doubled at the end of the LR 2001 compared to what was present and the end of the SR 2000/2001 season in all treatments. This shows that there is substantial amount of mineral N that is being leached below the rooting zone of maize in this region.  相似文献   

16.
A field experiment was conducted for two crop cycles during 2003–2005 and 2004–2006 at the Indian Institute of Sugarcane Research, Lucknow in subtropical India. Trichoderma viride and Gluconacetobacter diazotrophicus amended farm yard manure (FYM) increased organic carbon (19.44 Mg ha−1) and available nitrogen (260 kg N ha−1) content of soil from 14.78 Mg ha−1 (OC) and 204 kg N ha−1 observed under farmer's practice (sole N application). Application of bioagents amended FYM improved soil porosity and reduced compaction (bulk density—1.39 Mg m−3 over 1.48 Mg m−3 under farmer's practice). Sugarcane ratoon crop removed the highest amount of nitrogen (N—165.7 kg ha−1), phosphorus (P—24.01 kg ha−1) and potassium (K—200.5 kg ha−1) in the plots receiving FYM with Trichoderma and Gluconacetobacter. Inoculation of FYM with bioagents improved population of ammonifying and nitrifying bacteria in the soil. Phosphorus and potassium uptake of the crop was greatest in the plots receiving FYM, Trichoderma and Gluconacetobacter. Bioagents (Trichoderma and Gluconacetobacter) amended FYM increased ratoon cane (70.2 Mg ha−1) and sugar yields (7.93 Mg ha−1) compared with control (62.3 and 7.06 Mg ha−1 ratoon cane and sugar yields, respectively).  相似文献   

17.
Soil organic carbon (SOC) and nitrogen (N) are directly influenced by tillage, residue return and N fertilization management practices. Soil samples for SOC and N analyses, obtained from a 23-year field experiment, provided an assessment of near-equilibrium SOC and N conditions. Crops included corn (Zea mays L.) and soybean [Glycine max L. (Merrill)]. Treatments of conventional and conservation tillage, residue stover (returned or harvested) and two N fertilization rates were imposed on a Waukegan silt loam (fine-silty over skeletal, mixed, superactive, mesic Typic Hapludoll) at Rosemount, MN. The surface (0–20 cm) soils with no-tillage (NT) had greater than 30% more SOC and N than moldboard plow (MB) and chisel plow (CH) tillage treatments. The trend was reversed at 20–25 cm soil depths, where significantly more SOC and N were found in MB treatments (26 and 1.5 Mg SOC and N ha−1, respectively) than with NT (13 and 1.2 Mg SOC and N ha−1, respectively), possibly due to residues buried by inversion. The summation of soil SOC over depth to 50 cm did not vary among tillage treatments; N by summation was higher in NT than MB treatments. Returned residue plots generally stored more SOC and N than in plots where residue was harvested. Nitrogen fertilization generally did not influence SOC or N at most soil depths. These results have significant implications on how specific management practices maximize SOC storage and minimize potential N losses. Our results further suggest different sampling protocols may lead to different and confusing conclusions regarding the impact of tillage systems on C sequestration.  相似文献   

18.
Effects of two tillage treatments, tillage (T) with chisel plough and no-till (NT), were studied under un-drained and drained soil conditions. Soil physical properties measured were bulk density (ρb), total porosity (ƒt), water stable aggregates (WSA), geometric mean diameter (GMD), mean weight diameter (MWD), organic carbon (OC) and total N concentrations in different aggregate size fractions, and total OC and N pools. The experiment was established in 1994 on a poorly drained Crosby silt loam soil (fine mixed, mesic, Aeric Ochraqualf) near Columbus, Ohio. In 2007, soil samples were collected (0–10, 10–20, and 20–30 cm) from all treatments and separated into six aggregate size classes for assessing proportions of macro (5–8, 2–5, 1–2, 0.5–1, 0.25–0.5) and micro (<0.25 mm) aggregates by wet sieving. Tillage treatments significantly (P ≤ 0.05) influenced WSA, MWD, and GMD. Higher total WSA (78.53 vs. 58.27%), GMD (0.99 vs. 0.68 mm), and MWD (2.23 vs. 0.99 mm) were observed for 0–10 cm depth for NT than T treatments. Relative proportion of macro-aggregates (>0.25-mm) was also more in NT than T treatment for un-drained plots. Conversely, micro-aggregates (<0.25-mm) were more in T plots for both drained and un-drained treatments. The WSA, MWD and GMD decreased with increase in soil depth. The OC concentration was significantly higher (P ≤ 0.05) in NT for un-drained (P ≤ 0.01) treatment for all soil depths. Within macro-aggregates, the maximum OC concentrations of 1.91 and 1.75 g kg−1 in 1–2 mm size fraction were observed in NT for un-drained and drained treatments, respectively. Tillage treatments significantly (P < 0.01) affected bulk density (ρb), and total porosity (ft) for all soil depths, whereas tillage × drainage interaction was significant (P < 0.01) for 10–20 and 20–30 cm depths. Soil ρb was negatively correlated (r = −0.47; n = 12) with OC concentration. Tillage treatments significantly affected (P ≤ 0.05) OC pools at 10–20 cm depth; whereas drainage, and tillage × drainage significantly (P ≤ 0.05) influenced OC pools for 0–10 cm soil layer. The OC pool in 0–10 cm layer was 31.8 Mg ha−1 for NT compared with 25.9 Mg kg−1 for T for un-drained treatment. In comparison, the OC pool was 23.1 Mg ha−1 for NT compared with 25.2 Mg ha−1 for T for the drained plots. In general, the OC pool was higher in NT system, coupled with un-drained treatment than in drained T plots. The data indicate the importance of NT in improving the OC pool.  相似文献   

19.
Sustainable vegetable production especially during the dry season requires adequate conservation of soil water. This study was conducted to evaluate the sole and interactive effects of mulching (M) and poultry manure (PM) application on soil temperature (ST), crop evapotranspiration (ETc) and water use efficiency (WUE) of okra. The experiment was a Randomized Complete Block Design (RCBD) with three replicates. The treatments were M at 0 and 6 t ha−1 and PM at 0, 10 and 20 t ha−1. Soil temperature was measured using digital thermometer while ETc was determined by water depletion method using a Time Domain Reflectometer. Irrigation at field capacity was applied manually at 2-day intervals. Independent application of mulch significantly lowered ST while joint application of 20 t ha−1 PM (PM20) and M significantly (p ≤ 0.05) reduced ST at 5 cm and 10 cm soil depth compared with the unmulched plots in both seasons. Application of 10 t ha−1 PM (PM10) without M recorded the highest ETc (43.7 mm), while joint application of PM20 and M reduced ETc by about 93% compared with PM10 only. Okra used water most efficiently when PM20 was applied under mulched plot. There was 62.2% increase in WUE under mulched plots compared with the control while the residual effect of PM10 and M significantly increased WUE by 65.5%. It was evident that M alongside application of PM is a good strategy for regulating ST, moderating ETc and increasing okra WUE, especially during dry season farming.  相似文献   

20.
The one-compartment C model Ct=C0e−k2t+k1A/k2(1−e−k2t) is being long used to simulate soil organic C (SOC) stocks. Ct is the SOC stock at the time t; C0, the initial SOC stock; k2, the annual rate of SOC loss (mainly mineralization and erosion); k1, the annual rate to which the added C is incorporated into SOC; and A, the annual C addition. The component C0e−k2t expresses the decay of C0 and, for a time t, corresponds to the remains of C0 (C0 remains). The component k1A/k2(1−e−k2t) refers, at time t, to the stock of SOC derived from C crops (Ccrop). We herein propose a simple method to estimate k1 and k2 coefficients for tillage systems conducted in long-term experiments under several cropping systems with a wide range of annual C additions (A) and SOC stocks. We estimated k1 and k2 for conventional tillage (CT) and no-till (NT), which has been conducted under three cropping systems (oat/maize −O/M, vetch/maize −V/M and oat + vetch/maize + cowpea −OV/MC) and two N-urea rates (0 kg N ha−1 −0 N and 180 kg N ha−1 −180 N) in a long-term experiment established in a subtropical Acrisol with C0 = 32.55 Mg C ha−1 in the 0–17.5 cm layer. A linear equation (Ct = a + bA) between the SOC stocks measured at the 13th year (0–17.5 cm) and the mean annual C additions was fitted for CT and NT. This equation is equivalent to the equation of the model Ct=C0e−k2t+k1A/k2(1−e−k2t), so that a=C0e−k2t and bA=k1A/k2(1−e−k2t). Such equivalences thus allow the calculation of k1 and k2. NT soil had a lower rate of C loss (k2 = 0.019 year−1) than CT soil (k2 = 0.040 year−1), while k1 was not affected by tillage (0.148 year−1 under CT and 0.146 year−1 under NT). Despite that only three treatments had lack of fit (LOFIT) value lower than the critical 5% F value, all treatments showed root mean square error (RMSE) lower than RMSE 95% indicating that simulated values fall within 95% confidence interval of the measurements. The estimated SOC stocks at steady state (Ce) in the 0–17.5 cm layer ranged from 15.65 Mg ha−1 in CT O/M 0 N to 60.17 Mg ha−1 in NT OV/MC 180 N. The SOC half-life (t1/2 = ln 2/k2) was 36 years in NT and 17 years in CT, reflecting the slower C turnover in NT. The effects of NT on the SOC stocks relates to the maintenance of the initial C stocks (higher C0 remais), while increments in Ccrop are imparted mainly by crop additions.  相似文献   

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