Kemink subsoiling before and after planting

The Kemink exact soil management system is a non-inversion soil management system based on subsoiling, ridges and controlled traffic. Previous studies have documented benefits of the Kemink system used in its entirety, but the isolated effect of Kemink subsoiling has not been investigated before. To determine the isolated effect of Kemink subsoiling before and after planting two field experiments in sugar beet and barley were conducted in 1999 and 2000 under low nutrient input conditions in a conventional soil management system without recognized compaction problems. Kemink subsoiling after planting generally showed a negative effect on the growth and yield of both crops, whereas subsoiling before planting increased sugar beet yield from 8.4 to 9.5 t ha⁻¹ and sugar beet nitrogen uptake from 48.5 to 57.4 kg ha⁻¹. There was no effect of subsoiling before planting on the grain yield of barley. The negative effect of subsoiling after planting was more pronounced in 1999 than in 2000, and more pronounced in spring barley. The study shows that Kemink subsoiling after planting involves a significant risk of crop damage and cannot be expected to improve crop performance in conventional soil management systems in its current form, whereas Kemink subsoiling before planting may have potential as a measure to increase yield of sugar beet and possibly other row crops too, under low nutrient input conditions.     

Tillage and cropping effects on soil quality indicators in the northern Great Plains

The extreme climate of the northern Great Plains of North America requires cropping systems to possess a resilient soil resource in order to be sustainable. This paper summarizes the interactive effects of tillage, crop sequence, and cropping intensity on soil quality indicators for two long-term cropping system experiments in the northern Great Plains. The experiments, located in central North Dakota, were established in 1984 and 1993 on a Wilton silt loam (FAO: Calcic Siltic Chernozem; USDA¹: fine-silty, mixed, superactive frigid Pachic Haplustoll). Soil physical, chemical, and biological properties considered as indicators of soil quality were evaluated in spring 2001 in both experiments at depths of 0–7.5, 7.5–15, and 15–30 cm. Management effects on soil properties were largely limited to the surface 7.5 cm in both experiments. For the experiment established in 1984, differences in soil condition between a continuous crop, no-till system and a crop–fallow, conventional tillage system were substantial. Within the surface 7.5 cm, the continuous crop, no-till system possessed significantly more soil organic C (by 7.28 Mg ha⁻¹), particulate organic matter C (POM-C) (by 4.98 Mg ha⁻¹), potentially mineralizable N (PMN) (by 32.4 kg ha⁻¹), and microbial biomass C (by 586 kg ha⁻¹), as well as greater aggregate stability (by 33.4%) and faster infiltration rates (by 55.6 cm h⁻¹) relative to the crop–fallow, conventional tillage system. Thus, soil from the continuous crop, no-till system was improved with respect to its ability to provide a source for plant nutrients, withstand erosion, and facilitate water transfer. Soil properties were affected less by management practices in the experiment established in 1993, although organic matter related properties tended to be greater under continuous cropping or minimum tillage than crop sequences with fallow or no-till. In particular, PMN and microbial biomass C were greatest in continuous spring wheat (with residue removed) (22.5 kg ha⁻¹ for PMN; 792 kg ha⁻¹ for microbial biomass C) as compared with sequences with fallow (SW–S–F and SW–F) (Average=15.9 kg ha⁻¹ for PMN; 577 kg ha⁻¹ for microbial biomass C). Results from both experiments confirm that farmers in the northern Great Plains of North America can improve soil quality and agricultural sustainability by adopting production systems that employ intensive cropping practices with reduced tillage management.     

The effect of autumn ridging and inter-row subsoiling on potato tuber yield and quality on a sandy soil in Denmark

Autumn ridging is a modified version of the ridge tillage system. Instead of setting up ridges during the growing season, they are established in autumn and left for the winter. Previous studies have documented positive effects of autumn ridging on potato yield and we hypothesized that subsoiling could enhance these effects. To determine the effect of autumn ridging and inter-row subsoiling on potato yield and quality a field experiment was conducted on sandy soil from 2001 to 2003. Autumn ridging resulted in an average total and marketable tuber yield of 25.6 and 9.2 t ha⁻¹, which was not significantly different from the average total and marketable yield of 25.6 and 8.9 t ha⁻¹ with ploughing. However, autumn ridging significantly reduced the incidence of black scurf from 2.5% to 2.2%. Inter-row subsoiling in the growing season significantly increased marketable potato tuber yield from 8.4 to 9.6 t ha⁻¹ and reduced the occurrence of malformed potatoes from 9.3% to 7.5%, irrespective of tillage treatment and irrigation level. There was no significant interaction between autumn ridging and subsoiling. The beneficial effect of subsoiling on marketable yield was driven by a 48.5% increase in the dry year of 2001. Subsoiling reduced the incidence of common scab from 7.8% to 6.9% when irrigation was reduced. It is concluded that at least three factors may modify the effects of subsoiling: Soil water status in the growing season, precipitation immediately before and after the subsoiling operation, and crop growth stage at the time of subsoiling.     

Real-time Measures of Canopy Size as a Basis for Spatially Varying Nitrogen Applications to Winter Wheat sown at Different Seed Rates

Experiments at two sites growing winter wheat show that in order to manage a wheat canopy more effectively, the use of specific remote sensing techniques both to monitor crop canopy expansion, and to determine variable nitrogen applications at key timings is required. Variations in seed rate were used to achieve a range of initial crop structures, and treatments were compared to standard farm practice. In the first year, the effect of varying seed rate (250, 350 and 450 seeds m⁻²) on crop structure, yield components and grain yield, was compared to the effects of underlying spatial variation. Plant populations increased up to the highest rate, but shoot and ear populations peaked at 350 seeds m⁻². Compensation through an increased number of grains per ear and thousand grain weight resulted in the highest yield and gross margin at the lowest seed rate. In later experiments, the range of seed rates was extended to include 150 seeds m⁻², each sown in 24 m wide strips split into 12 m wide halves. One half received a standard nitrogen dose of 200 kg [N] ha⁻¹, the other a variable treatment based on near ‘real-time’ maps of crop growth. Both were split into three applications, targeted at mid-late tillering (early March), growth stages GS30-31 (mid April) and GS33 (mid May). At each timing, calibrated aerial digital photography was used to assess crop growth in terms of shoot population at tillering, and canopy green area index at GS30-31 and GS33. These were compared to current agronomic guidelines. Application rates were then varied below or above the planned amount where growth was above- or below-target, respectively. In the first field, total nitrogen doses in the variable treatments ranged from 188 to 243 kg [N] ha⁻¹, which gave higher yields than the standards at all seed rates in the range 0·36–0·78 t ha⁻¹ and gross margins of £17 to £60 ha⁻¹. In the second field, variable treatments ranged from 135 to 197 kg [N] ha⁻¹ that resulted in lower yields of −0·32 to +0·30 t ha⁻¹. However, in three out of the four seed rates, variable treatments produced higher gross margins than the standard, which ranged from £2 to £20 ha⁻¹. In both fields, the greatest benefits were obtained where the total amount of applied nitrogen was similar to the standard, but was applied variably rather than uniformly along the strips. Simple nitrogen balance calculations have shown that variable application of nitrogen can have an overall effect on reducing the nitrogen surplus by one-third.     

Soil water conservation and yield of winter sorghum (Sorghum bicolor L. Moench) as influenced by tillage, organic materials and nitrogen fertilizer in semi-arid tropical India

Soil water and nutrients play an important role in increasing sorghum (Sorghum bicolor L. Moench) yields in the Vertisols of semi-arid tropics during post-rainy season. The effects of tillage practices, organic materials and nitrogen fertilizer on soil properties, water conservation and yield of sorghum were evaluated during winter seasons of 1994–1995 and 1995–1996 on deep Vertisols at Bijapur in the semi-arid tropics of Karnataka State (Zone 3) of south India. Conservation and availability of water and nutrients during different stages of crop growth were increased by deeper tillage resulting in increased grain yield of winter sorghum. Medium and deep tillage increased the grain yield by 23% (1509 kg ha⁻¹) and 57% (1919 kg ha⁻¹) during 1994–1995 and 14% (1562 kg ha⁻¹) and 34% (1835 kg ha⁻¹) during 1995–1996, respectively, over shallow tillage. Water use efficiency increased from shallow (4.90 kg ha⁻¹ mm⁻¹) to deep tillage (7.30 kg ha⁻¹ mm⁻¹). Greater water use efficiency during 1994–1995 as compared to 1995–1996 was attributed to lower consumptive use of water during 1994–1995. Among organic materials, application of Leucaena loppings conserved larger amounts of water and increased winter sorghum yield and water use efficiency. Application of Leucaena loppings increased the winter sorghum grain yield by 9% (mean of 1994–1995 and 1995–1996) as compared to vermicompost. Significantly (P < 0.05) higher water use efficiency of 6.32 kg ha⁻¹ mm⁻¹ was observed in Leucaena loppings incorporated plots compared to 5.72 kg ha⁻¹ mm⁻¹ from vermicompost. Grain yield increased by 245 kg ha⁻¹ with application of 25 kg N ha⁻¹ in 1994–1995, and a further increase in N application to 50 kg ha⁻¹ increased the grain yield by about 349 kg ha⁻¹ in 1995–1996. Deep tillage with application of 25 kg N ha⁻¹ resulted in significantly higher sorghum yield (2047 kg ha⁻¹) than control during 1994–1995. Deep tillage with integrated nutrient management (organic and inorganic N sources) conserved higher amount of soil water and resulted in increased sorghum yields especially during drought years.     

Physical changes and compaction sensitivity of a fine-textured, poorly drained soil (Typic Endoaquept) under varying durations of cropping, Manawatu Region, New Zealand

The physical deterioration of soil under continuous cropping is a problem in many humid, temperate areas. While soils of the Kairanga Series (Typic Endoaquept), Manawatu Region, North Island, New Zealand, are widely used for continuous cereal production, there is concern over the long-term sustainability of this land use. We report the results of a field experiment conducted on a sequence of sites on Kairanga soils, with cropping durations of 0, 4 and 28 years. Study objectives were to quantify physical differences between these soils and to assess a field method for measuring sensitivity to further compaction. Significant changes in key soil physical properties were recorded between the pasture and cropped sites in the 0–30 cm depth range. Most changes had occurred within the first 4 years of cropping. Physical properties that changed significantly included macropore volume (>60 μm), air capacity volume (>30 μm), air permeability, saturated hydraulic conductivity, unsaturated hydraulic conductivity (−0.4 kPa), and shear strength. Bulk density increased significantly only after a long cropping period, and penetration resistance measurements did not significantly differentiate sites of increasing cropping duration. Hence, bulk density and penetration resistance measurements on their own may not be adequate to assess cropping impact. Agricultural tractors were used under moist spring conditions to impose wheel traffic at an intensity of 273–305 Mg km ha⁻¹ on the study sites. The wheel traffic experiment confirmed the trends revealed by the initial site sampling, and also indicated that both soil deformation and soil compaction were the operational forms of soil disturbance at a soil water matric potential of −10 kPa. Soil physical conditions at the long-term cropped site (28 years) had stabilised and were in equilibrium with the soil’s biological and physical environments, while the short-term cropped site (4 years) was still in a transition state, with the likelihood of further increases in bulk density and shear strength. To start appropriate amelioration, it is important to identify when soils are in transition between pasture and long-term cropped states.     

Carbon sequestration and relationship between carbon addition and storage under rainfed soybean–wheat rotation in a sandy loam soil of the Indian Himalayas

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.     

Effect of time of mulching on soil temperature and moisture regime and emergence, growth and yield of white yam in western Nigeria

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.     

Carbon input, loss and storage in sub-tropical Indian Inceptisol under multi-ratooning sugarcane

Changes in residue management and incorporation of organic manures may help in carbon sequestration, restoring soil organic carbon (SOC) and sustaining the productivity of land under a cropping system. An experiment of multi-ratooning sugarcane (Saccharum officinarum L.) was initiated in 2003 in Inceptisols of Indian subtropics, to assess the effect of different organic manures and chemical fertilizer, on the crop productivity and soil quality. The annual sugarcane shoot biomass production in organic manure treatments was at par with the chemically fertilized treatment. Gross input of carbon (GIC) by the sugarcane crop was estimated to be 11.7–12.4 t ha⁻¹ y⁻¹ in different organic manure treatments compared to 8.4 and 5.0 t ha⁻¹ y⁻¹ in NPK and control treatments, respectively. The respiratory loss of C (RLC) increased linearly with increasing input of C in soil and it ranged from 3.3 to 4.1 t ha⁻¹ y⁻¹ in different treatments with maximum in FYM and minimum in control treatment. The sugarcane biomass added in the soil humified at a rate constant of 0.38 in sub-tropical conditions and an addition of 3.9 t C ha⁻¹ y⁻¹ is required to maintain SOC in equilibrium. After 5 years of sugarcane cropping (one plant + four ratoons) an increase of 2.3–17.1 t ha⁻¹ in SOC over initial content was recorded with different treatments. Results in coming years from this long-term experiment shall add to the present calculated relationships between carbon addition and storage in sugarcane multi-ratooning crop production system under sub-tropical condition of India.     

Effects of tillage, weed control method and row spacing on soybean yield and certain soil properties

Soybean (Glycine max (L.) Merr.) is an important crop in the southeastern United States, and thus there is a need for additional information on the effects of tillage, weed control methods and row spacing on soybean yields, weed populations and soil properties. The objective of this study was to determine the effects of three weed control methods (none, cultivation, and herbicide) and three row spacings (45, 60 and 90 cm) on soybeans planted in a conventionally prepared seedbed or planted in wheat stubble (no-till (NT)) on a Decatur silty clay loam (Rhodic Paleudult) soil during the 1987 and 1988 growing seasons. Following NT planting, soybean plots produced a seed yield of 3102 kg ha⁻¹ with herbicide, 2911 kg ha⁻¹ with cultivation and 2216 kg ha⁻¹ with no weed control. On a conventionally prepared seedbed, herbicide and cultivation resulted in almost equal seed yields (3898 kg ha⁻¹ and 3954 kg ha⁻¹ respectively) which were significantly higher than those from the no weed control plots (3151 kg ha⁻¹). Soybeans in narrow (45 cm) rows (3997 kg ha⁻¹) consistently out-yielded those in the wider 60 cm rows (3130 kg ha⁻¹) and 90 cm rows (2490 kg ha⁻¹) in both growing seasons, results averaged across years showed that conventionally planted soybeans produced higher yields (3668 kg ha⁻¹) than NT planted soybeans (2743 kg ha⁻¹). The weed infestation was significantly less with herbicide or cultivation than with no weed control and also less in narrow rows (45 cm) than in wider rows (60 and 90 cm). Data on the soil properties (from a depth of 0–15 cm) showed that moisture content, organic matter content and total soil nitrogen were higher in NT plots than in conventional plots. Similarly, disease ratings and infestation of bacterial blight of soybean were significantly higher in NT than in conventional tillage systems.     

Influence of crop residue management, cropping system and N fertilizer on soil N and C dynamics and sustainable wheat (Triticum aestivum L.) production

Management of N is the key for sustainable and profitable wheat production in a low N soil. We report results of irrigated crop rotation experiment, conducted in the North West Frontier Province (NWFP), Pakistan, during 1999–2002 to evaluate effects of residue retention, fertilizer N application and mung bean (Vigna radiata) on crop and N yields of wheat and soil organic fertility in a mung bean–wheat sequence. Treatments were (a) crop residue retained (+residue) or (b) removed (−residue), (c) 120 kg N ha⁻¹ applied to wheat, (d) 160 kg N ha⁻¹ to maize or (e) no nitrogen applied. The cropping system was rotation of wheat with maize or wheat with mung bean. The experiment was laid out in a spit plot design. Postharvest incorporation of crop residues significantly (p < 0.05) increased the grain and straw yields of wheat during both years. On average, crop residues incorporation increased the wheat grain yield by 1.31 times and straw yield by 1.39 times. The wheat crop also responded strongly to the previous legume (mung bean) in terms of enhanced grain yield by 2.09 times and straw yield by 2.16 times over the previous cereal (maize) treatment. Application of fertilizer N to previous maize exerted strong carry over effect on grain (1.32 times) and straw yield (1.38 times) of the following wheat. Application of N fertilizer to current wheat produced on average 1.59 times more grain and 1.77 times more straw yield over the 0 N kg ha⁻¹ treatment. The N uptake in wheat grain and straw was increased 1.31 and 1.64 times by residues treatment, 2.08 and 2.49 times by mung bean and 1.71 and 1.86 times by fertilizer N applied to wheat, respectively. The soil mineral N was increased 1.23 times by residues, 1.34 times by mung bean and 2.49 times by the application of fertilizer N to wheat. Similarly, the soil organic C was increased 1.04-fold by residues, 1.08 times by mung bean and 1.00 times by the application of fertilizer N. We concluded that retention of residues, application of fertilizer N and involvement of legumes in crop rotation greatly improves the N economy of the cropping system and enhances crop productivity in low N soils.     

Poultry litter and tillage influences on corn production and soil nutrients in a Kentucky silt loam soil

Broiler chicken (Gallus gallus) manure, a rich source of plant nutrients, is generated in large quantities in southeastern USA where many row crops, such as corn (Zea mays L.), are also extensively grown. However, the use of broiler manure as an economical alternative source of nutrients for corn production has not been extensively explored in this region. This study was conducted to examine the use of broiler litter as a source of nutrients for corn production, as influenced by tillage and litter rate, and any residual effects following application. In addition, the consequence of litter application to soil test nutrient levels, particularly P, Zn and Cu, was explored. The treatments consisted of two rates of broiler litter application, 11 and 22 Mg ha⁻¹ on a wet weight basis, and one rate of chemical fertilizer applied under no-till and conventional tillage systems. Treatments were replicated three times in a randomized complete block design. Corn was grown with broiler litter and inorganic fertilizer applied to the same plots each year from 1998 to 2001. In 2002 and 2003, corn was planted no-till, but only N fertilizer was applied in order to make use of other residual litter nutrients. Soil samples were taken yearly in the spring prior to litter application and 4 years after the cessation of litter application to evaluate the status of the residual nutrients in soil. Two years out of the 4-year experiment, broiler litter application produced significantly greater corn grain yield than equivalent chemical fertilizer application and produced similar grain yield in the other 2 years. Corn grain yield was significantly greater under no-till in 1999, but significantly greater under conventional-till in 2000, and no difference between the two tillage systems were observed in 1998 and 2001. With 4 years of litter application, Mehlich-3 P increased from an initial 18 mg kg⁻¹ to 156 mg kg⁻¹ with 11 Mg ha⁻¹ litter and to 257 mg kg⁻¹ with 22 Mg ha⁻¹ litter. For every 6 kg ha⁻¹ of P applied in poultry litter Mehlich-3 P was increased by 1 mg kg⁻¹. Modest increases in Mehlich-3 Cu and Zn did not result in phytotoxic levels. This study indicated that an optimum rate of broiler litter as a primary fertilizer at 11 Mg ha⁻¹ applied in 4 consecutive years on a silt loam soil produced corn grain yields similar to chemical fertilizer under both no-till and conventional tillage systems and kept soil test P, Cu and Zn levels below values considered to be harmful to surface water quality or the crop.     

Aggregation in a surface layer of a hardsetting and crusting soil as influenced by the application of amendments and grass mulch in a South African semi-arid environment

Hardsetting and crusting are forms of soil structure degradation associated with the collapse of macroaggregates during wetting and are responsible for poor seedling emergence, crop establishment and yields of food crops especially in semi-arid environments. This study investigated the effects of applying of 3.0 t ha⁻¹ phosphogypsum, 1.0 t ha⁻¹ polymer gel, 3.0 t ha⁻¹ grass mulch and 5.0 t ha⁻¹ cattle manure to the topsoil (0–15 cm) of a soil with hardsetting and crusting behavior and observed changes on aggregation under field conditions for two consecutive seasons. There were significant improvements in soil aggregate properties in the amended soil over the control. Both aggregate size distribution and wet aggregate stability showed significant differences between the amendments in the two seasons. The mean weight diameters of aggregates were 4.23 mm (mulch), 3.31 mm (manure), 2.17 mm (polymer gel), 2.23 mm (phosphogypsum) and 1.36 mm (control). The aggregates (2–4 mm) from amended soil were consistently more stable than the control and were in the order polymer gel = manure > mulch > gypsum > control. Tensile strength and bulk density of aggregates, on the other hand, were significantly higher (P < 0.05) in the unamended than amended soil.The application of soil amendments, especially mulch, significantly increased the soil water content over the two seasons and this was associated with lower soil penetration resistance in the latter. The reduced soil strength in the amended soils contributed to higher pegging, podding and grain yields of bambara groundnut (Vigna subterranean). This was confirmed by significantly higher correlations between soil aggregate characteristics, soil water, penetrometer resistance and growth and yield of bambara groundnut. The study concluded that significant improvements in soil aggregation can be obtained over a relatively short period and this can improve the yield of food crops.     

Carbon and nitrogen stocks in a Brazilian clayey Oxisol: 13-year effects of integrated crop–livestock management systems

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.     

Improving rhizospheric environment and sugarcane ratoon yield through bioagents amended farm yard manure in udic ustochrept soil

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).     

Crop growth and nitrogen transformations in wheat (Triticum aestivum L.) planted after wetland rice (Oryza sativa L.)

Summary A field study was undertaken to examine the effects of various management strategies on wheat (Triticum aestivum L.) performance and N cycling in an intensively cropped soil. Microplots receiving 100 kg N ha^–1 as¹⁵NH₄ ^{+ 15}NO₃ ^– at sowing, tillering or stem elongation were compared with unfertilized microplots. Stubble from the previous rice crop was either incorporated, burnt without tillage, burnt then tilled or retained on the surface of untilled soil. Wheat grain yield ranged from 1.5 to 5.1 t ha^– and was closely related to N uptake. Plant accumulation of soil N averaged 36 kg N ha^–1 (LSD 5% = 10) on stubble-incorporation plots and 54 kg N ha^–1 on stubble-retention plots. Fertilizer N accumulation averaged 18 kg N ha^–1 (LSD 51% = 6) on stubble-incorporation plots and 50 kg N ha^–1 on stubble-retention plots. Tillage had little effect on burnt plots. Delaying N application from sowing until stem elongation increased average fertilizer N uptake from 26 to 39 kg N ha^–1 (LSD 5% = 6), but reduced soil N uptake from 50 to 37 kg N ha^– (LSD 5% = 10).Immobilization and leaching did not vary greatly between treatments and approximately one-third of the fertilizer was immobilized. Less than 1% of the fertilizer was found below a depth of 300 mm. Incorporating 9 t ha^–1 of rice stubble 13 days before wheat sowing reduced net apparent mineralization of native soil N from 37 to 3 kg ha^–1 between tillering and maturity. It also increased apparent denitrification of fertilizer N from an average 34 to 53 kg N ha^–1 (LSD 5% = 6). N loss occurred over several months, suggesting that denitrification was maintained by continued release of metabolizable carbohydrate from the decaying rice stubble. The results demonstrate that no-till systems increase crop yield and use of both fertilizer and soil N in intensive rice-based rotations.     

Effects of crop growth and soil treatments on microbial C,N, and P in dry tropical arable land

We studied the dynamics of microbial C, N, and P in soil cropped with rice (Oryza sativa) and lentils (Lens culinaris) in a dryland farming system. The crop biomass and grain yield were also studied. The microbial biomass and its N and P contents were larger under the lentil than under the rice crop. Microbial nutrients decreased as the crops grew and then increased again. Farmyard manure and NPK fertilizer applications increased the level of microbial nutrients, crop biomass, and grain yield by 35–80%, 55–85%, and 74–86%, respectively. However, these applications had no significant effect on most of the soil physicochemical properties in the short term. The microbial biomass was correlated with the crop biomass and grain yield. The calculated flux of N and P through the microbial biomass ranged from 30–45 and 10–19 kg ha^-1 year^-1, respectively. Cultivation of a cereal crop followed by a leguminous crop sustains higher levels of microbial nutrients and hence greater fertility in impoverished tropical arable soils. The soil microbial biomass appears to contribute significantly to crop productivity by releasing nutrients, and applications of manure, either alone or with fertilizers, promote this effect more strongly than the application of NPK fertilizers alone.     

Quality of seedbed and ridges for potatoes as affected by low ground pressure, compared with normal and zero ground pressure

The influence of ground pressure by field traffic on soil structure and on growth and yield of potatoes, in a crop rotation of onions, potatoes, winterwheat and sugarbeet, was investigated in a “low ground pressure” experiment from 1985 to 1989 on the experimental husbandry farm “De Oostwaardhoeve”. Low ground pressures (L) of 50–100 kPa, with relatively wide tires, were compared with conventional (high) ground pressures (H) of 100–300 kPa with relatively narrow tires, and with zero ground pressure (Z) on inner ridges of beds four rows wide. The quality (amount and crumbling) of the loose soil in the seedbed, in the ridges and after harvesting of the potatoes, was investigated. With a decrease in ground pressure from H to L to Z, the amount of dry loose soil in the ridges increased from 93.6 kg m⁻² to 95.1 kg m⁻² and to 99.9 kg m⁻², the mean weighed diameter decreased from 6.0 mm to 5.4 mm and to 4.7 mm and the total increase yield from 57.1 t ha ⁻¹ to 59.4 t ha⁻¹ and to 62.9 t ha⁻¹, respectively. Differences in amount and crumbling of the loose soil and yield were larger between and zero ground pressure than between low and conventional (high) ground pressure plots.     

Planting methods and nitrogen effects on crop yield and soil quality under direct seeded rice in the Indo-Gangetic plains of eastern India

A field trial was conducted during the kharif (rainy) seasons of 2002 and 2003 at the Research Farm, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India. The trial was carried out to study the effect of planting methods, sources and levels of nitrogen on soil properties, yield and NPK uptake by rice (Oryza sativa L.) under direct seeded condition. Planting methods significantly influenced the physical, chemical and biological properties of soil. Bulk density (1.385 g cm⁻³), organic carbon (0.43%) and soil moisture content (15.46%) were higher in zero till seeding plots than rotavator and conventional seeding. However, infiltration rate, soil temperature, pH and electrical conductivity showed a declining trend under this treatment and were found maximum (11.54 mm h⁻¹, 36.21 °C at 55 DAS, 30.65 °C at harvest, 7.59 and 0.47 ds m⁻¹) with conventional seeding. The maximum population of bacteria (25.60 × 10⁵), fungi (14.26 × 10⁴) and azotobactor (10.19 × 10³) were found in the plot with zero till seeding while in case of actinomycetes the highest population (25.61 × 10⁵) was found in conventional seeding. Nitrogen sources as well as levels failed to bring about any significant change in the soil properties. The highest grain (3825 kg ha⁻¹) and straw yields (5446 kg ha⁻¹) and N, P, K uptake were recorded in conventional seeding and were found significantly superior to zero till seeding (3144 kg ha⁻¹) but it remained at par with rotavator seeding (3585 kg ha⁻¹). Among the nitrogen sources, neem (Azadirachta indica) coated urea produced significantly higher grain (3761 kg ha⁻¹) and straw yields (5396 kg ha⁻¹) with greater NPK uptake than prilled urea and prilled urea + spent mentha. (The distillation waste of mint (Mentha arvensis) herbage is known as spent mentha.) Application of 150 kg N ha⁻¹ produced maximum grain (3828 kg ha⁻¹) and straw yields (5460 kg ha⁻¹) although it remained at par with 100 kg N ha⁻¹ (3738 and 5393 kg ha⁻¹).     

Contour furrows for in situ soil and water conservation, Tigray, Northern Ethiopia

In Tigray (Northern Ethiopia), soil moisture has been identified as the most limiting factor in agricultural production; on the other hand, loss of rain water through runoff as well as the induced soil loss has been determined as a critical problem in the region in the last two to three decades. To alleviate the above paradox, the government has mobilized communities and resources for the construction of physical soil and water conservation structures (stone bunds, terraces) in almost all land uses. However, yield improvement was mainly concentrated within the vicinity of the structures and runoff continued to overtop the structures, as no measures for in situ soil conservation were taken. The terwah system, consisting of traditional ploughing followed by making every 1.5–2 m contour furrows, and permanent raised beds with contour furrows at 60–70 cm interval treatments, were considered and evaluated as practices that could increase the efficiency of in situ water utilization and soil conservation. An experiment was started in Gum Selasa, which is one of the drought prone areas in Tigray, whereby runoff volume and sediment load were measured after every rain event. Permanent raised beds with contour furrows at 60–70 cm interval significantly (P < 0.05) reduced runoff volume, runoff coefficient and soil loss as compared to traditional ploughing: 255, 381 and 653 m³ ha⁻¹ runoff was recorded from permanent bed, terwah and traditional ploughing, respectively during the whole cropping season. The above runoff induced 4.7 t ha⁻¹ soil loss from permanent bed, 7.6 t ha⁻¹ from terwah and 19.5 t ha⁻¹ from traditional ploughing. Overall, contour furrows and permanent raised beds can be part of the ongoing intensification process which includes physical soil and water conservation, slope reforestation, irrigation development and agro forestry in crop lands. Moreover, the use of permanent raised beds if combined with crop mulching and crop diversification is an important component for the development of sustainable conservation agriculture practices in the region.