Soil properties influencing erodibility of soils in the Ntabelanga area,Eastern Cape Province,South Africa

Soil erosion has serious off-site impacts caused by increased mobilization of sediment and delivery to water bodies causing siltation and pollution. To evaluate factors influencing soil erodibility at a proposed dam site, 21 soil samples collected were characterized. The soils were analyzed for soil organic carbon (SOC), exchangeable bases, exchangeable acidity, pH, electrical conductivities, mean weight diameter and soil particles’ size distribution. Cation exchange capacity, exchangeable sodium percentage, sodium adsorption ratio, dispersion ratio (DR), clay flocculation index (CFI), clay dispersion ratio (CDR) and Ca:Mg ratio were then calculated. Soil erodibility (K-factor) estimates were determined using SOC content and surface soil properties. Soil loss rates by splashing were determined under rainfall simulations at 360?mmh^?1 rainfall intensity. Soil loss was correlated to the measured chemical and physical soil properties. There were variations in soil form properties and erodibility indices showing influence on soil loss. The average soil erodibility and SOC values were 0.0734?t?MJ^?1?mm^?1 and 0.81%, respectively. SOC decreased with depth and soil loss increased with a decrease in SOC content. SOC significantly influenced soil loss, CDR, CFI and DR (P??1. Addition of organic matter stabilize the soils against erosion.     

Assessing spatial variability and erosion susceptibility of soils in hilly agricultural areas in Southern Italy

Soil erosion is one of the main environmental problems in the Mediterranean area. This problem is becoming even more important especially in Italy, in the Apennines, where severe erosive processes occur due to the action of concentrated running water. The erodibility (K-Factor) of a soil, estimated using the Revised Universal Soil Loss Equation (RUSLE), is a measure of its susceptibility to erosion and depends on several soil properties such as organic matter, texture and permeability and structure.To assess the spatial variability of soil properties and soil erodibility in hilly agricultural areas and to investigate the relationships between soil features and landscape morphodynamics, a detailed study in Molise region (southern Italy), in a small drainange basin located along its hilly Adriatic flank, was carried out. In this catchment, 63 topsoil samples (A horizons) were collected and 10 soil profiles, forming a catena crossing 3 land units, were sampled. The calculated K-Factors ranges between 0.012 and 0.048 t ha h ha⁻¹ MJ⁻¹ mm⁻¹ indicating a complex spatial distribution, due to the several local pedological and geomorphological factors affecting soil erodibility. The results give clear evidence about the relationships among soil characteristics, soil erodibility and landscape morpho-dynamics (land units).Comparing the soil loss rates estimated for the study area with those reported in literature, a good correspondence can be observed only for the more stable land unit, not characterized by intense erosive processes. The proposed methodology is suitable to highlight areas characterized by similar morphodynamics features, and comparable soil erodibility, for a more effective spatialization of K factor.     

Nutrient fluxes from a soil treatment process for pig slurry

Abstract. The effects of pig slurry applications to a hydrologically isolated field treatment plant (at Solepur) were studied over a period of eight years. Thirty repeated doses, averaging 160 m³ ha^?1 were applied from April to October of each year (1991–1995), to reach a total application of 4930 m³ ha^?1. All slurry samples were analysed for their total solids (TS), macronutrient (C, N, P, K, Ca) and micronutrient (Cu, Zn) content. In total, 284 tonnes of total solids (57 t TS ha^?1 yr^?1), 115 tonnes of carbon (23 t C ha^?1yr^?1), 24.5 tonnes of nitrogen (4900 kg N ha^?1 yr^?1), 7964 kg of phosphorus (1593 kg P ha^?1 yr^?1), 16 518 kg of potassium (3304 kg K ha^?1 yr^?1), 183 kg copper (37 kg Cu ha^?1 yr^?1) and 266 kg zinc (53 kg Zn ha^?1 yr^?1) were applied to the soil. Thus, this site provides an opportunity to assess the balance and to examine the long‐term behaviour of nutrients under conditions of intensive land application of pig slurries or similar effluents. The main nutrient fluxes through the soil‐water system were determined for each element. Over 40% of the total carbon applied was retained by the soil. About 25% of the slurry nitrogen applied remained in the soil profile and 12.5% was leached through the drainage water as nitrate. Most of the slurry phosphorus applied was retained in the soil profile either as P‐Dyer extractable (83%), or as total soil phosphorus (112%); <0.01% was found in the drainage water. Forty‐three per cent of the potassium applied in the slurry was recovered from the soil profile and 15% was recovered in the drainage water. Most of the copper (62%) and zinc (74%) applied in the slurry remained in the soil as EDTA extractractable forms; very low percentages (0.05% and 0.6% respectively) were found in the drainage water.     

Erodibility of soils of the upper rainforest zone,southeastern Nigeria

The susceptibility of some soils in the high rainfall zone of Nigeria to soil erosion must be measured regularly for better soil management. A number of techniques have been adopted for the determination of this soil loss parameter. The aim of this study is to determine the soil characteristics that relate significantly to erodibility. Soil samples collected from 0–20 cm depth from 10 different locations in the upper rainforest area were analysed for particle size distribution, water‐stable aggregates, exchangeable cations, organic carbon, soil dispersion and aggregating indices. The soils are mainly Acrisols, Nitosols, Gleysols and Ferralsol in the FAO classification while their textures are sands to sandy‐clay‐loam. They are very unstable in water as reflected in the higher values of WSA >0·50 mm and the mean‐weight diameter that ranged from 0·50 to 2·03 mm. The dispersion ratio for the soils are between 0·26 and 0·69 while clay dispersion ratio also ranged from 0·24 to 0·80. Revised universal soil loss equation (RUSLE) erodibility model values (K) were from 0·03 to 0·06 Mg h MJ⁻¹ mm⁻¹. These parameters can be effectively used in predicting soil erodibility, though their predictability varied in ranking of soil erodibility. In spite of this variability these indices can be used for potential erosion hazard determination by agricultural extension staff to avoid crop failures and other negative influence of soil erosion. The soil parameters are easy to determine and will be a valuable instrument when faster approaches to erosion control measures are required. Copyright © 2003 John Wiley & Sons, Ltd.     

Eucalyptus biochar application enhances Ca uptake of upland rice,soil available P,exchangeable K,yield, and N use efficiency of sugarcane in a crop rotation system

It was hypothesized that the application of eucalyptus biochar enhances nutrient use efficiencies of simultaneously supplied fertilizer, as well as provides additional nutrients (i.e., Ca, P, and K), to support crop performance and residual effects on subsequent crops in a degraded sandy soil. To test this hypothesis, we conducted an on‐farm field experiment in the Khon Kaen province of Northeastern Thailand to assess the effects of different application rates of eucalyptus biochar in combination with mineral fertilizers to upland rice and a succeeding crop of sugarcane on a sandy soil. The field experiment consisted of three treatments: (1) no biochar; (2) 3.1 Mg ha^?1 biochar (10.4 kg N ha^?1, 3.1 kg P ha^?1, 11.0 kg K ha^?1, and 17.7 kg Ca ha^?1); (3) 6.2 Mg ha^?1 biochar (20.8 kg N ha^?1, 6.2 kg P ha^?1, 22.0 kg K ha^?1, and 35.4 kg Ca ha^?1). All treatments received the same recommended fertilizer rate (32 kg N ha^?1, 14 kg P ha^?1, and 16 kg K ha^?1 for upland rice; 119 kg N ha^?1, 21 kg P ha^?1, and 39 kg K ha^?1 for sugarcane). At crop harvests, yield and nutrient contents and nitrogen (N) use efficiency were determined, and soil chemical properties and pH₀ monitored. The eucalyptus biochar material increased soil Ca availability (117 ± 28 and 116 ± 7 mg kg^?1 with 3.1 and 6.2 Mg ha^?1 biochar application, respectively) compared to 71 ± 13 mg kg^?1 without biochar application, thus promoting Ca uptake and total plant biomass in upland rice. Moreover, the higher rate of eucalyptus biochar improved CEC, organic matter, available P, and exchangeable K at succeeding sugarcane harvest. Additionally, 6.2 Mg ha^?1 biochar significantly increased sugarcane yield (41%) and N uptake (70%), thus enhancing N use efficiency (118%) by higher P (96%) and K (128%) uptake, although the sugar content was not increased. Hence, the application rate of 6.2 Mg ha^?1 eucalyptus biochar could become a potential practice to enhance not only the nutrient status of crops and soils, but also crop productivity within an upland rice–sugarcane rotation system established on tropical low fertility sandy soils.     

Nutrient‐enriched soils and native N‐fixing plants in New Zealand

Approximately 40% of New Zealand's land mass is fertilized grassland with entirely non‐native plants, but currently there is substantially increased interest in restoration of native plants into contemporary agricultural matrices. Native vegetation is adapted to more acid and less fertile soils and their establishment and growth may be constrained by nutrient spillover from agricultural land. We investigated plant–soil interactions of native N‐fixing and early successional non N‐fixing plants in soils with variable fertility. The effects of soil amendments of urea (100 and 300 kg N ha^?1), lime (6000 kg CaCO₃ ha^?1), and superphosphate (470 kg ha^?1) and combinations of these treatments were evaluated in a glasshouse pot trial. Plant growth, soil pH, soil mineral N, Olsen P and nodule nitrogenase activity in N‐fixing plants were measured. Urea amendments to soil were not inhibitory to the growth of native N‐fixing plants at lower N application rates; two species responded positively to combinations of N, P and lime. Phosphate enrichment enhanced nodulation in N‐fixers, but nitrogen inhibited nodulation, reduced soil pH and provided higher nitrate concentrations in soil. The contribution of mineral N to soil from the 1‐year old N‐fixing plants was small, in amounts extrapolated to be 10–14 kg ha^?1 y^?1. Urea, applied both alone and in conjunction with other amendments, enhanced the growth of the non N‐fixing species, which exploited mineral N more efficiently; without N, application of lime and P had little effect or was detrimental. The results showed native N‐fixing plants can be embedded in agroecology systems without significant risk of further increasing soil fertility or enhancing nitrate leaching.     

Erodibility in relation to water‐dispersible clay for some soils of eastern Nigeria

Water dispersible clay (WDC) can influence soil erosion by water. Therefore, in highly erodible soils such as the ones in eastern Nigeria, there is a need to monitor the clay dispersion characteristics to direct and modify soil conservation strategies. Twenty‐five soil samples (0–20 cm in depth) varying in texture, chemical properties and mineralogy were collected from various locations in central eastern Nigeria. The objective was to determine the WDC of the soils and relate this to selected soil physical and chemical attributes. The soils were analysed for their total clay (TC), water‐dispersible clay (WDC), clay dispersion ratio (CDR), dispersion ratio (DR), dithionite extractable iron (Fed), soil organic matter (SOM), exchangeable cations, exhangeable sodium percentage (ESP) and sodium adsorption ratio (SAR). Total clay contents of the soil varied from 80–560 g kg⁻¹. The USLE erodibility K ranges from 0·02 to 0·1 Mg h MJ⁻¹ mm and WEPP K fall between 1·2 × 10⁻⁶–1·7 × 10⁻⁶ kg s m⁻⁴. The RUSLE erodibility K correlated significantly with CDR and DR (r = 0·44; 0·39). Also, a positive significant correlation (r = 0·71) existed between WEPP K and RUSLE K. Soils with high clay dispersion ratio (CDR) are highly erodibile and positively correlates (p < 0·51) with Fed, CEC and SOM. Also, DR positively correlates with Mg²⁺ and SOM and negatively correlate with ESP and SAR. Principal component analysis showed that SAR, Na⁺ and percent base saturation play significant role in the clay dispersion of these soils. The implication of this result is that these elements may pose potential problem to these soils if not properly managed. Copyright © 2005 John Wiley & Sons, Ltd.     

Potassium‐fertilizer management in winter oilseed‐rape production in China

Optimal potassium (K) fertilization is beneficial for oilseed‐rape (Brassica napus L.) yield and quality. However, the discrepancy between the high K demand of winter oilseed rape and low soil fertility and insufficient potassium input has limited the sustainable development of oilseed‐rape production. A series of on‐farm experiments in the key winter oilseed‐rape domains of China was conducted from 2004 to 2010 to evaluate K‐fertilizer management for winter oilseed rape. Currently, the average NH₄OAc‐extractable K content in the 0–20 cm soil layer is 89.1 mg kg^–1 indicative of “slight deficiency”. In addition, farmers in China usually fail to use sufficient K fertilizer in oilseed‐rape production, the average mineral‐potassium‐fertilizer input in 2010 being only 35 kg K ha^–1, far lower than the recommended rate of potassium for winter oilseed rape. Adequate potassium fertilization significantly raises seed yield. The average yield‐increase rate for the major production regions due to K‐fertilizer application was 18.5%, and the average K fertilizer–use efficiency 36.1%. Based on the negative correlation between yield response to potassium fertilization and available soil K content, a soil‐K‐test index was established for winter oilseed rape with a threshold value for NH₄OAc‐extractable soil K of 135 mg kg^–1. When available soil K‐content is below this threshold value, more K fertilizer should be applied to achieve high seed yield and to increase soil fertility. The major challenge for K‐fertilizer management in winter oilseed‐rape production in China will be to guide farmers in the different regions in making reasonable use of K fertilizer through soil K‐testing technology in order to maintain both seed yield and soil fertility.     

Variability of soil physical quality and erodibility in a water-eroded cropland

Physical degradation of the soil increases its susceptibility to erosion by water action. However, relatively few studies have evaluated the opposite, i.e., the impact of water erosion on soil erodibility. This study was conducted in a corn field in Ohio. Some sites within the field have experienced water-induced soil erosion following heavy rainstorms. Physical characteristics of the soil were compared between eroded (ER) and un-eroded sites (UN). Compared with ER, the soil in UN had lower penetration resistance (4.87 vs. 4.53 MPa), bulk density (1.45 vs. 1.33 Mg m^?3), and sand content (17.4 vs. 14.2%), and higher shear strength (80.1 vs. 125.3 KPa), hydraulic conductivity (3.0 vs. 3.4 cm h^?1), intrinsic permeability (31.9 vs. 36.4 × 10^?10 cm²), and contents of soil organic carbon (36.1 vs. 32.1 g kg^?1), total nitrogen (3.3 vs. 3.1 g kg^?1), clay (25.2 vs. 24.2%), silt (60.5 vs. 58.4%), and very fine sand (3.4 vs. 1.1%). Also Munsell's variables differed between ER and UN (1.24 vs. 0.54 for hue, 4.59 vs. 4.35 for value, and 1.99 vs. 1.79 for chroma, respectively). The erodibility factor (K) was lower in UN than in ER (0.00327 vs. 0.00354 Mg ha h ha^?1 MJ^?1 mm^?1, respectively). Hence, it is suggested the ER sites within the corn field agroecosystem are more susceptible to accelerated erosion as compared with UN sites.     

Long‐term effects of fertilization on some soil properties under rainfed soybean‐wheat cropping in the Indian Himalayas

This study aims to examine the effects of long‐term fertilization and cropping on some chemical and microbiological properties of the soil in a 32 y old long‐term fertility experiment at Almora (Himalayan region, India) under rainfed soybean‐wheat rotation. Continuous annual application of recommended doses of chemical fertilizer and 10 Mg ha^–1 FYM on fresh‐weight basis (NPK + FYM) to soybean (Glycine max L.) sustained not only higher productivity of soybean and residual wheat (Triticum aestivum L.) crop, but also resulted in build‐up of total soil organic C (SOC), total soil N, P, and K. Concentration of SOC increased by 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 was 29% and that from wheat was 24% of the harvestable aboveground biomass yield. Annual gross C input and annual rate of total SOC enrichment from initial soil in the 0–15 cm layer were 4362 and 333 kg C ha^–1, respectively, for the plots under NPK + FYM. It was observed that the soils under the unfertilized control, NK and N + FYM treatments, suffered a net annual loss of 5.1, 5.2, and 15.8 kg P ha^–1, respectively, whereas the soils under NP, NPK, and NPK + FYM had net annual gains of 25.3, 18.8, and 16.4 kg P ha^–1, respectively. There was net negative K balance in all the treatments ranging from 6.9 kg ha^–1 y^–1 in NK to 82.4 kg ha^–1 y^–1 in N + FYM–treated plots. The application of NPK + FYM also recorded the highest levels of soil microbial‐biomass C, soil microbial‐biomass N, populations of viable and culturable soil microbes.     

Effects of Long-Term Fertilizer Application and Rainfall Distribution on Cotton Productivity,Profitability, and Soil Fertility in a Semi-arid Vertisol

Long-term fertilizer experiments were conducted on cotton (Gossypium hirsutum) for 21 years with eight fertilizer treatments in a fixed site during 1987–2007 to identify an efficient treatment to ensure maximum yield, greater sustainability, monetary returns, rainwater-use efficiency, and soil fertility over years. The results indicated that the yield was significantly influenced by fertilizer treatments in all years except 1987 1988, and 1994. The mean cotton yield ranged from 492 kg ha^?1 under the control to 805 kg ha^?1 under 25 kg nitrogen (N) [farmyard manure (FYM)] + 25 kg N (urea) + 25 kg phosphorus (P) ha^?1. Among the nutrients, soil N buildup was observed with all treatments, whereas application of 25 kg N + 12.5 kg P ha^?1 exhibited increase in P status. Interestingly, depletion of potassium (K) was recorded under all the fertilizer treatments as there was no K application in any of the treatments. An increase in soil N and P increased the plant N and P uptake respectively. Using relationships of different variables, principal component (PC) analysis technique was used for assessing the efficiency of treatments. In all the treatments, five PCs were found significant that explained the variability in the data of variables. The PC model of 25 kg N (FYM) + 25 kg N (urea) + 25 kg P ha^?1 explained maximum variability of 79.6% compared to other treatments. The treatment-wise PC scores were determined and used in developing yield prediction models and measurement of sustainability yield index (SYI). The SYI ranged from 44.4% in control to 72.7% in 25 kg N (FYM) + 25 kg N (urea) + 25 kg P ha^?1, which attained a mean cotton yield of 805 kg ha^?1 over years. Application of 25 kg N (FYM) + 25 kg N (urea) + 25 kg P ha^?1 was significantly superior in recording maximum rainwater-use efficiency (1.13 kg ha^?1 mm^?1) and SYI (30.5%). This treatment also gave maximum gross returns of Rs. 30272 ha^?1 with benefit–cost ratio of 1.60 and maintained maximum organic carbon and available N, P, and K in soil over years. These findings are extendable to cotton grown under similar soil and agroclimatic conditions in any part of the world.     

Suitability of Lime,Green Leaf,and Farm Yard Manure and Inorganic Fertilizers for Sustaining Green Gram Yield and Rainwater Use Efficiency Under Moist Sub-Humid Alfisols in India

Field experiments were conducted to assess the effect of nutrients management practices on yield and rainwater use efficiency of green gram (Vigna radiata), and soil fertility under moist sub-humid Alfisols at Phulbani, India, during 2005–2008. Ten treatment combinations of lime @ 10% and 20% of lime requirement (LR) @ 8.3 t ha^?1, farmyard manure (FYM) @ 5 t ha^?1, green leaf manure @ 5 t ha^?1, and nitrogen, phosphorus, and potassium (N–P–K) (20–40–20 kg ha^?1) were tested. The analysis of variance indicated that treatments differed significantly from each other in influencing yield and rainwater use efficiency. Application of lime @ 20% LR + FYM @ 5 t/ha + 40 kg P + 20 kg K ha^?1 was superior with maximum mean yield of 531 kg ha^?1, while lime @ 10% LR + FYM @ 5 t ha^?1 + 40 kg P + 20 kg K ha^?1 was the second best with 405 kg ha^?1 and maintained maximum soil fertility of nutrients. The superior treatment gave maximum sustainability yield index of 67.5%, rainwater use efficiency of 0.49 kg ha^?1 mm^?1, improved soil pH, electrical conductivity, and soil nutrients over years.     

Residual tillage and bush-fallow effects on soil properties and maize intercropped with legumes on a tropical Alfisol

Abstract. After six years of bush‐fallow, residual effects on soil productivity of tillage practices prior to the fallow were investigated on an Alfisol in south western Nigeria. In 1996 fallow was followed by maize intercropped with cover crops of Pueraria phaseoloides, Mucuna pruriens or cowpea (Vigna unguiculata) and no intercrop. Parameters measured included soil properties, ground cover, crop growth and yield, rainfall erosivity, runoff and soil loss. In spite of six‐years of bush‐fallow and establishment of cover crops, soil erosion was significantly greater on plots that had been conventionally cultivated previously using disc ploughs, harrows and mechanical rotovators (1.78 t ha^?1season^?1) compared to previously no‐till plots (1.34 t ha^?1season^?1). Crop growth and yields were least and soil loss greatest (2.83 t ha^?1season^?1) on the previous bare plot. Maize grain yield was highest using Pueraria phaseoloides as an intercrop (2.15 t ha^?1) followed by a cowpea intercrop (1.92 t ha^?1), maize without intercrop (1.87 t ha^?1) and Mucuna pruriens intercrop (1.71 t ha^?1). The maize grain yields reflected levels of competition from the cover crops. Cowpea–maize intercrop may be most suitable for farmers because maize yields were satisfactory and cowpea grain serves as additional subsistence. Cowpea yields were 390 kg ha^?1. Soil erosion was also moderate using cowpea as an intercrop (1.71 t ha^?1season^?1). However, Pueraria phaseoloides gave the best erosion control with a soil loss of 1.34 t ha^?1season^?1.     

Potassium fertilization on sandy soils in relation to soil test,crop yield and K-leaching

To study the influence of potassium (K) fertilizer rate on soil test K values, crop yield, and K-leaching in sandy soils, four long-term fertilizer experiments (0–60–120–180 kg K ha^?1 a^?1) were initiated in 1988 in northern Germany on farmers fields. Clay content of the plow layer was about 4%, and organic matter between 2% and 5%. Plant available soil K was estimated with the double lactate (DL) method. Small grain cereals (rye and barley) did not respond to K fertilization in the 7-year period even though the soil test value of the K-0 plots decreased from ca. 90 to ca. 30 mg K_DL kg^?1 within 3 years. This value remained almost constant thereafter. Crop removal (including straw) of 75 kg K ha^?1 a^?1 was therefore apparently supplied from nonexchangeable K fractions. Compared to the optimum, no K application reduced the yield of potato by up to 21%, and that of white sugar yield up to 10%. Maximum potato yield was obtained by annually applying 60 kg K ha^?1 which resulted in a test value of 60 mg K_DL kg^?1 soil. Maximum potato yield was also obtained at 40 mg K_DL kg^?1 soil, however, with a single application of 200 kg K ha^?1. Similar results were obtained with sugar beet. This indicates that for maximum yield, even for K demanding crops, it is not necessary to maintain K_DL values above 40 mg K kg^?1 soil throughout the entire crop rotation. Soil test values increased roughly proportional to the K fertilizer level. About 120 kg fertilizer K ha^?1 a^?1, markedly more than crop K removal, was required to maintain the initial K_DL of 90 mg kg^?1. The K concentration of the soil solution in the top soil measured after harvest was increased exponentially by K fertilizer level and so was K leaching from the plow layer into the rooted subsoil. The leached quantity increased from 22 kg K ha_?1 a_?1 in the plot without K application to 42.79 and 133 kg Kha^?1 a^?1 in plots supplied with 60, 120 and 180 kg K ha^?1 a^?1 respectively. Soil test values around 100 mg K_DL kg^?1 on sandy soils, as often found in the plow layer of farmers fields, lead to K leaching below the root zone that may exceed the critical K concentration of 12 mg K T^?1 for drinking water.     

Nutrient storage in termite (Macrotermes bellicosus) mounds and the implications for nutrient dynamics in a tropical savanna Ultisol

The role of mounds of the fungus-growing termite Macrotermes bellicosus (Smeathman) in nutrient recycling in a highly weathered and nutrient-depleted tropical red earth (Ultisol) of the Nigerian savanna was examined by measuring stored amounts of selected nutrients and estimating their rates of turnover via the mounds. A study plot (4?ha) with a representative termite population density (1.5?mounds?ha^?1) and size (3.7?±?0.4?m in height, 2.4?±?0.2?m in basal diameter) of M. bellicosus mounds was selected. The mounds were found to contain soil mass of 9249?±?2371?kg?ha^?1, composed of 7502?±?1934?kg?ha^?1 of mound wall and 1747?±?440?kg?ha^?1 of nest body. Significant nutrient enrichment, compared to the neighboring topmost soil (Ap1 horizon: 0–16?cm), was observed in the nest body for total nitrogen (N) and exchangeable calcium (Ca), magnesium (Mg) and potassium (K), and in the mound wall for exchangeable K only. In contrast, available (Bray-1) phosphorus (P) content was found to be lower in both the mound wall and the nest body than in the adjacent topmost soil horizon. Consequently, the mounds formed by M. bellicosus contained 1.71?±?0.62?kg?ha^?1 of total N, 0.004?±?0.003?kg?ha^?1 of available P, 3.23?±?0.81?kg?ha^?1 of exchangeable Ca, 1.11?±?0.22?kg?ha^?1 of exchangeable Mg and 0.79?±?0.21?kg?ha^?1 of exchangeable K. However, with the exception of exchangeable K (1.2%), these nutrients amounted to less than 0.5% of those found in the topmost soil horizon. The soil nutrient turnover rate via M. bellicosus mounds was indeed limited, being estimated at 1.72?kg?ha^?1 for organic carbon (C), 0.15?kg?ha^?1 for total N, 0.0004?kg?ha^?1 for available P, 0.15?kg?ha^?1 for exchangeable Ca, 0.05?kg?ha^?1 for exchangeable Mg, and 0.06?kg?ha^?1 for exchangeable K per annum. These findings suggest that the mounds of M. bellicosus, while being enriched with some nutrients to create hot spots of soil nutrients in the vicinity of the mounds, are not a significant reservoir of soil nutrients and are therefore of minor importance for nutrient cycling at the ecosystem scale in the tropical savanna.     

Potassium leaching from cut grassland and from urine patches

In grassland farming, especially on coarse‐textured soils, K can be a critical element. On these soils, the actual K management as well as fertilizer history to a large extent determine the leaching of K. The effects of four fertilizer regimes on the nutrient balances and leaching of K from grassland grown on a sandy soil were investigated. The swards differed in the source and level of N input and K fertilizer: no fertilizer N + 166 kg K ha^?1 year^?1 (Control), 320 kg inorganic N ha^?1 + 300 kg K ha^?1 year^?1 (MIN 320), 320 kg N + 425 kg K ha^?1 year^?1 in form of cattle slurry (SLR 320) and a grass–clover sward + 166 kg K ha^?1 year^?1 (WCL 0) without any inorganic N input. In a second experimental phase, cores from these swards were used in a mini‐lysimeter study on the fate of K from urine patches. On cut grassland after 6 years K input minus removal in herbage resulted in average K surpluses per year of 47, 39, 56 and 159 kg K ha^?1 for the Control, MIN 320, WCL 0 and SLR 320, respectively. Related leaching losses per year averaged 7.5, 5, 15 and 25 kg K ha^?1. Losses of urinary‐K through leaching were 2.2–4.5 and 5.7–8.4% of the K supplied in summer and autumn applications, respectively. Plant and soil were the major sinks for K from fertilizer or urine. High levels of exchangeable K in the soil and/or large and late fertilizer or urine applications stimulated leaching of K.     

Bio‐inoculant improves nitrogen‐use efficiency and cotton yield in saline soils

Improved nutrient‐use efficiency is important to sustain agricultural production. The goal of our study was to investigate the effects of Azovit® (Azotobacter chroococcum) inoculation of seed with N fertilization on crop yield, nutrient uptake, and N‐use efficiency (NUE) of irrigated cotton (Gossypium hirsutum L. cv. C‐6524) in secondary saline soil under continental climatic conditions of Uzbekistan. A randomized complete block design in a 4 × 2 split‐plot experiment was established in the fall of 2013. The main plot was N fertilization (0, 140, 210, and 280 kg ha^?1) and the subplot was Azovit inoculation. Azovit inoculation consistently increased the seed and lint yields of cotton by 25 and 27.9%, respectively, at 210 kg N ha^?1 compared to the respective control. Azovit with 210 kg N ha^?1 significantly increased the cotton harvest index by 21%, when compared to the control. Likewise, nutrient uptake and NUE of cotton were higher when N (210 kg ha^?1) was applied with Azovit, as compared to other treatment combinations. An extrapolation of the relationship of relative yield vs. N fertilization showed that Azovit at 210 kg N ha^?1 was sufficient to obtain near‐maximum cotton production (90%) with highest NUE, as compared to the respective control. The results suggest that Azovit with 210 kg N ha^?1 produces cotton yield higher and/or comparable with the currently used rates of 280 kg N ha^?1 or higher, suggesting savings of 70 kg N ha^?1 for cotton production in saline soils under continental climatic conditions.     

Potassium fertilization and soil diagnostic criteria for forage corn (Zea mays L.) production contributing to lower potassium input in regional fertilizer recommendation

Abstract

Effective soil diagnostic criteria for exchangeable potassium (Ex-K) combined with inorganic potassium (K) application rates were developed to lower K input in forage corn (Zea mays L.) production using experimental fields with different application rates and histories of cattle manure compost. Two corn varieties, ‘Cecilia’ as a low K uptake variety and ‘Yumechikara’ as a high K uptake variety, were selected from among 20 varieties and tested to make diagnostic criteria for K fertilization applicable to varieties with different K uptakes. The K uptakes increased from 96 to 303 kg K ha^?1 for ‘Cecilia’ and from 123 to 411 kg K ha^?1 for ‘Yumechikara’ with increasing Ex-K content on a dry soil basis from 0.11 to 0.92 g kg^?1 with no inorganic K fertilizer application. The K uptake by corn for achieving the target dry matter yield of 18 Mg ha^?1 was estimated to be approximately 200 kg K ha^?1 in common between the two varieties. Yields of both varieties achieved the target yield at an Ex-K content of approximately 0.30 g kg^?1 with no K fertilization, although ‘Yumechikara’ reached the target yield at a lower Ex-K content. At the low Ex-K content of 0.1 g kg^?1, inorganic K fertilizer application at 83 kg K ha^?1 was needed to gain the target yield, and apparent K recovery rate for K fertilizer was calculated to be 70% for both varieties. The K uptakes for gaining the target yield by the K fertilization were lower than that by soil K supply. Based on these results, diagnostic criteria of Ex-K and inorganic K application rates were set up as follows: at an Ex-K content of < 0.15 g kg^?1, inorganic K fertilizer is applied at 83 kg K ha^?1 (100 kg ha^?1 as potassium oxide (K₂O) equivalent); at an Ex-K content of 0.15–0.30 g kg^?1, the application rate is reduced to 33 kg K ha^?1 (40 kg K₂O ha^?1); at an Ex-K content of ≥ 0.30 g kg^?1, inorganic K fertilizer is not applied because of sufficient K in the soil. Additionally, we propose that cattle manure compost be used to supplement soil K fertility.     

Influence of Soil and Fertilizer Nutrients on Sustainability of Rainfed Finger Millet Yield and Soil Fertility in Semi-arid Alfisols

Productivity of rainfed finger millet in semiarid tropical Alfisols is predominantly constrained by erratic rainfall, limited soil moisture, low soil fertility, and less fertilizer use by the poor farmers. In order to identify the efficient nutrient use treatment for ensuring higher yield, higher sustainability, and improved soil fertility, long term field experiments were conducted during 1984 to 2008 in a permanent site under rainfed semi-arid tropical Alfisol at Bangalore in Southern India. The experiment had two blocks—Farm Yard Manure (FYM) and Maize Residue (MR) with 5 fertilizer treatments, namely: control, FYM at 10 t ha^?1, FYM at 10 t ha^?1 + 50% NPK [nitrogen (N), phosphorus (P), potassium (K)], FYM at 10 t ha^?1 + 100% NPK (50 kg N + 50 kg P + 25 kg K ha^?1) and 100% NPK in FYM block; and control, MR at 5 t ha^?1, MR at 5 t ha^?1 + 50% NPK, MR at 5 t ha^?1 + 100% NPK and 100% NPK in MR block. The treatments differed significantly from each other at p < 0.01 level of probability in influencing finger millet grain yield, soil N, P, and K in different years. Application of FYM at 10 t ha^?1 + 100% NPK gave a significantly higher yield ranging from 1821 to 4552 kg ha^?1 with a mean of 3167 kg ha^?1 and variation of 22.7%, while application of maize residue at 5 t ha^?1 + 100% NPK gave a yield of 593 to 4591 kg ha^?1 with a mean of 2518 kg ha^?1 and variation of 39.3% over years. In FYM block, FYM at 10 t ha^?1 + 100% NPK gave a significantly higher organic carbon (0.45%), available N (204 kg ha^?1), available P (68.6 kg ha^?1), and available K (107 kg ha^?1) over years. In maize residue block, application of MR at 5 t ha^?1 + 100% NPK gave a significantly higher organic carbon (0.39%), available soil N (190 kg ha^?1), available soil P (47.5 kg ha^?1), and available soil K (86 kg ha^?1). The regression model (1) of yield as a function of seasonal rainfall, organic carbon, and soil P and K nutrients gave a predictability in the range of 0.19 under FYM at 10 t ha^?1 to 0.51 under 100% NPK in FYM block compared to 0.30 under 100% NPK to 0.67 under MR at 5 t ha^?1 application in MR block. The regression model (2) of yield as a function of seasonal rainfall, soil N, P, and K nutrients gave a predictability in the range of 0.11 under FYM at 10 t ha^?1 to 0.52 under 100% NPK in FYM block compared to 0.18 under MR at 5 t ha^?1 + 50% NPK to 0.60 under MR at 5 t ha^?1 application in MR block. An assessment of yield sustainability under different crop seasonal rainfall situations indicated that FYM at 10 t ha^?1 + 100% NPK was efficient in FYM block with a maximum Sustainability Yield Index (SYI) of 41.4% in <500 mm, 64.7% in 500–750 mm, 60.2% in 750–1000 mm and 60.4% in 1000–1250 mm rainfall, while MR at 5 t ha^?1 + 100% NPK was efficient with SYI of 29.6% in <500 mm, 50.2% in 500–750 mm, 40.6% in 750–1000 mm, and 39.7% in 1000–1250 mm rainfall in semi-arid Alfisols. Thus, the results obtained from these long term studies incurring huge expenditure provide very good conjunctive nutrient use options with good conformity for different rainfall situations of rainfed semiarid tropical Alfisol soils for ensuring higher finger millet yield, maintaining higher SYI, and maintaining improved soil fertility.     

Soil-Test-Based Optimum Fertilizer Doses for Attaining Yield Targets of Rice under Midland Alfisols of Eastern India

Soil-test crop-response experiments on rice were conducted in the Bastar Plateau Agroclimatic Zone of Chhattisgarh during 2009–2011 to assess yield, soil, plant, and fertilizer nitrogen (N), phosphorus (P), and potassium (K) nutrient relationships and calibrate optimum fertilizer doses for attaining yield targets. Soil fertility status was poor to medium for N (194–283 kg ha^?1) and P (7.53–19.66 kg ha^?1), and medium to good for K (226–320 kg ha^?1). Based on nutrient requirements (NR, kg q^?1) and contributions from soil (CS, %), fertilizer (CF, %), and farmyard manure (CFYM, %), optimum fertilizer doses were derived. The fertilizer doses were validated for attaining yield targets of 5000 and 6000 kg ha^?1 in farmer’s fields. Rice yield within 10% deviation was attained, which indicated that soil-test-based fertilizer dose was superior. This approach could be adopted for regions with similar soil and agroclimatic conditions in other parts of the world to increase rice yields.