Long-term tillage,straw management and N fertilization effects on quantity and quality of organic C and N in a Black Chernozem soil

Soil, crop and fertilizer management practices may affect the amount and quality of organic C and N in soil. A long-term field experiment (growing barley, wheat, or canola) was conducted on a Black Chernozem (Albic Argicryoll) loam at Ellerslie, Alberta, Canada, to determine the influence of 19 (1980 to 1998) or 27 years (1980 to 2006) of tillage (zero tillage [ZT] and conventional tillage [CT]), straw management (straw removed [S_Rem]and straw retained [S_Ret]) and N fertilizer rate (0, 50 and 100 kg N ha⁻¹ in S_Ret and 0 kg N ha⁻¹ in S_Rem plots) on total organic C (TOC) and N (TON), and light fraction organic C (LFOC) and N (LFON) in the 0–7.5 and 7.5–15 cm or 0–5, 5–10 and 10–15 cm soil layers. The mass of TOC and TON in soil was usually higher in S_Ret than in S_Rem treatment (by 3.44 Mg C ha⁻¹ for TOC and 0.248 Mg N ha⁻¹ for TON after 27 years), but there was little effect of tillage and N fertilization on these parameters. The mass of LFOC and LFON in soil tended to increase with S_Ret (by 285 kg C ha⁻¹ for LFOC and 12.6 kg N ha⁻¹ for LFON with annual rate of 100 kg N ha⁻¹ for 27 years)_, increased with N fertilizer application (by 517 kg C ha⁻¹ for LFOC and 36.0 kg N ha⁻¹ for LFON after 27 years), but was usually higher under CT than ZT (by 451 kg C ha⁻¹ for LFOC and 25.3 kg N ha⁻¹ for LFON after 27 years). Correlations between soil organic C or N fractions were highly significant in most cases. Linear regressions between crop residue C input and soil organic C or N were significant in most cases. The effects of tillage, straw management and N fertilizer on soil were more pronounced for LFOC and LFON than TOC and TON, and also in the surface layers than in the deeper layers. Tillage and straw management had little or no effect on C:N ratios, but the C:N ratios in light organic fractions significantly decreased with increasing N rate (from 20.06 at zero-N to 18.91 at 100 kg N ha⁻¹). Compared to the 1979 results, in treatments that did not receive N fertilizer (CTS_Rem0, CTS_Ret0, ZTS_Rem0 and ZTS_Ret0), CTS_Rem0 resulted in a net decrease in TOC concentration (by 1.9 g C kg⁻¹) in the 0–15 cm soil layer in 2007 (after 27 years), with little or no change in the CTS_Ret0 and ZTS_Rem0 treatments, while there was a net increase in TOC concentration (by 1.2 g C kg⁻¹) in the ZTS_Ret0 treatment. Straw retention and N fertilizer application at 50 and 100 kg N ha⁻¹ rates showed a net positive effect on TOC concentration under both ZT (ZTS_Ret50 by 2.3 g C kg⁻¹ and ZTS_Ret100 by 3.1 g C kg⁻¹) and CT (CTS_Ret50 by 3.5 g C kg⁻¹ and CTS_Ret100 by 1.6 g C kg⁻¹) treatments in 2007 compared to 1979 data. In conclusion, the findings suggest that retention of straw, application of N fertilizer and elimination of tillage would improve soil quality, and this might increase the potential for N supplying power of the soil and sustainability of crop productivity.     

平衡施肥对莴笋产量和品质的效应研究

采用田间试验研究了不同氮磷钾配比及其与硝酸盐复合控制剂配施对莴笋产量和品质的影响。结果表明,不同施肥处理莴笋产量有显著差异,BNPK处理莴笋产量最高,HNP处理最低,HNK+C2和HNK+C3处理使莴笋增产6.2%和4.1%。HNK配施硝酸盐复合控制剂对莴笋茎硝酸盐的降低幅度较大。综合产量和品质,以HNK+C2处理效果最好。     

Erratum to: Long-term tillage,straw and N rate effects on quantity and quality of organic C and N in a Gray Luvisol soil

Long-term use of soil, crop residue and fertilizer management practices may affect some soil properties, but the magnitude of change depends on soil type and climatic conditions. Two field experiments with barley, wheat, or canola in a rotation on Gray Luvisol (Typic Cryoboralf) loam at Breton and Black Chernozem (Albic Argicryoll) loam at Ellerslie, Alberta, Canada, were conducted to determine the effects of 19 or 27 years (from 1980 to 1998 or 2006 growing seasons) of tillage (zero tillage [ZT] and conventional tillage [CT]), straw management (straw removed [S_Rem] and straw retained [S_Ret]) and N fertilizer rate (0, 50 and 100 kg N ha⁻¹ in S_Ret, and 0 kg N ha⁻¹ in S_Rem plots) on pH, extractable P, ammonium-N and nitrate–N in the 0–7.5, 7.5–15, 15–30 and 30–40 cm or 0–15, 15–30, 30–60, 60–90 and 90–120 cm soil layers. The effects of tillage, crop residue management and N fertilization on these chemical properties were usually similar for both contrasting soil types. There was no effect of tillage and residue management on soil pH, but application of N fertilizer reduced pH significantly (by up to 0.5 units) in the top 15 cm soil layers. Extractable P in the 0–15 cm soil layer was higher or tended to be higher under ZT than CT, or with S_Ret than S_Rem in many cases, but it decreased significantly with N application (by 18.5 kg P ha⁻¹ in Gray Luvisol soil and 20.5 kg P ha⁻¹ in Black Chernozem soil in 2007). Residual nitrate–N (though quite low in the Gray Luvisol soil in 1998) increased with application of N (by 17.8 kg N ha⁻¹ in the 0–120 cm layer in Gray Luvisol soil and 23.8 kg N ha⁻¹ in 0–90 cm layer in Black Chernozem soil in 2007) and also indicated some downward movement in the soil profile up to 90 cm depth. There was generally no effect of any treatment on ammonium-N in soil. In conclusion, elimination of tillage and retention of straw increased but N fertilization decreased extractable P in the surface soil. Application of N fertilizer reduced pH in the surface soil, and showed accumulation and downward leaching of nitrate–N in the soil profile.     

Increasing organic C and N in soil under bromegrass with long-term N fertilization

Two field experiments were conducted on bromegrass (Bromus inermis Leyss.) on a thin Black Chernozem (Typic Boroll) at Crossfield, Alberta, Canada to determine the long-term effects of N fertilization on changes in concentration and mass of organic C and N in soil. In both experiments, bromegrass was harvested for hay each year. In the experiment where ammonium nitrate (AN) was applied annually at 0 to 336 kg N/ha for 27 consecutive years from 1968 to 1994, the concentration of total C in the 0–5 cm soil layer increased from 50.33 g/kg in the zero-N treatment to 61.64 g/kg with 56 kg N/ha and to 64.15 g/kg with the 112 kg N/ha rate. Total C in soil also increased in the 5–10, 10–15 and 15–30 cm layers but to a lesser extent. The mass of total C in the 0–30 cm soil layer was increased by 18.46 Mg/ha with 56 kg N/ha and by 23.38 Mg/ha with the 112 kg N/ha rate as compared to the zero-N treatment. Total N in soil followed a similar trend as total C. In the experiment which received four N sources [ammonium nitrate (AN), urea, calcium nitrate (CN) and ammonium sulphate (AS)] applied annually at 168 and 336 kg N/ha for 15 years from 1979 to 1993, the total C in soil was greater where N fertilizer was applied, but the increase in total C varied with N source. The concentration of total C in soil in the 0–5 cm layer tended to be greater with AN and AS than with CN, with the smallest increase from urea. The mass of total C in soil (average of four N sources) at the 168 kg N/ha rate was increased by 18.98 Mg/ha in 0–30 cm and by 43.48 Mg/ha in the 0–60 cm layer as compared to the check treatment. The concentration of total C in soil also increased in the deeper layers to a depth of 60 cm, but the increases were much smaller than in the 0–5 cm layer. The changes in total N in soil followed a similar pattern as total C. In conclusion, long-term annual additions of fertilizer N to bromegrass resulted in a marked increase in total C and N in soil and the increases were influenced by both rate and source of N fertilizer. The implications of these results are that grasslands can be managed to lessen the increase in atmospheric CO₂ concentration, while also improving fertility (N-supplying capacity) and tilth of soil. This revised version was published online in August 2006 with corrections to the Cover Date.     

不同施肥方式对水稻生长、养分吸收和品质的影响

研究不同施肥方式对田间水稻生长、养分吸收和品质的影响。结果表明,施肥能显著提高水稻产量,增产幅度在7.62%~41.90%,NPK与有机肥配合施用、施用控释肥分别增产31.75%和41.90%,氮磷钾对水稻增产作用NKP。氮肥农学利用率以缓控释肥处理最高,达11.08 kg/kg,氮肥利用率最高与最低相差31.10%;氮磷钾施肥+有机肥处理和控释肥处理田面水中速效氮含量显著低于其他处理,稻米品质最好。     

Long-term effects of fertilization and manuring on groundnut yield and nutrient balance of Alfisols under rainfed farming in India

Drought stress, uncertain and variable rainfall, low soil quality and nutrient deficiencies are among principal constraints for enhancing and sustaining agronomic productivity in rainfed farming in semiarid tropical regions of India. Therefore, long-term (1985–2004) effects of cropping, fertilization, manuring (groundnut shells, GNS; farmyard manure, FYM) and integrated nutrient management practices were assessed on pod yields, nutrient status and balances for a groundnut (Arachis hypogaea) monocropping system. The five nutrient management treatments were: control (no fertilizer); 100 % recommended dose of fertilizer (RDF) (20:40:40 N, P, K); 50 % RDF + 4 Mg ha^?1 GNS; 50 % RDF + 4 Mg ha^?1 FYM and 100 % organic (5 Mg ha^?1 FYM). All treatments were replicated four times. The experiment was conducted at Anantapur district, Andhra Pradesh on an Alfisol using a Randomized Complete Block design. The gap in pod yields between control and different nutrient treatments widened with increase in duration of cultivation. Use of diverse fertilizer and manurial treatments produced significantly higher yields than control (P < 0.05). Amount and distribution of rainfall during critical growth stages was more important to agronomic yield than total and seasonal rainfall. Thus, the amount of rainfall received during pegging stage (r = 0.47; P < 0.05) and pod formation stage (r = 0.50; P < 0.05) was significantly correlated with the mean pod yields. Whereas, use of diverse fertility management practices improved nutrient status in soil profiles (N, P, K, S, Ca, Mg, Zn, Fe, Mn and B) after 20 years of cropping, yet soil available N, K and B remained below the critical limits. Long-term cultivation also caused deficiency of S, Zn and B, which limited the groundnut productivity. Crop removal of N, P and K during 20 years of cultivation was more in 50 % RDF + 4 Mg ha^?1 GNS at 523, 210 and 598 kg ha^?1, respectively. With the exception of control, there was a positive nutrient balance of NPK in all other treatments. Higher positive balance of N and K were observed in 50 % RDF + 4 Mg ha^?1 GNS (616 and 837 kg ha^?1, respectively), and those of P in 100 % RDF (655 kg ha^?1) treatment. There was also a net depletion of available S, Zn, Cu and Mn, but a buildup of available Ca, Mg and Fe. Application of equal amount of GNS was as effective as or even better than FYM in terms of pod yields and nutrient buildup in the soil.     

河南省小麦、玉米及蔬菜优质高产高效平衡施肥

介绍农作物高产优质施肥技术的田间试验研究情况。田间试验结果表明:小麦在氮磷肥配施时(N270kg/hm2、P2O5120kg/hm2),K2O最佳用量为180kg/hm2,小麦最高产量达6880kg/hm2;玉米在氮磷肥配施时(N225kg/hm2、P2O5120kg/hm2),K2O最佳用量为180kg/hm2,玉米最高产量达7640kg/hm2;萝卜在氮磷肥配施时(N300kg/hm2、P2O5225kg/hm2),K2O最佳用量为300kg/hm2,萝卜最高产量达79860kg/hm2;白菜在氮磷肥配施时(N300kg/hm2、P2O5225kg/hm2),K2O最佳用量为300kg/hm2,白菜最高产量达95050kg/hm2。     

Biomass and nutrient uptake ofAilanthus excelsa as affected by N and P fertilization on an aridisol

A field experiment was conducted on a coarse sand soil having pH 8.8 and organic matter 0.06% in Indian arid region, to study the influence of N and P fertilizers on growth, biomass and nutrient content ofAilanthus excelsa, which is an important fodder species of arid and semi arid regions. Three levels of nitrogen (0, 9 and 18 g N tree^–1 as Urea) and of phosphorus (0, 3 and 6 g P₂O₅ tree^–1 as Single Superphosphate) in factorial combinations were taken in triplicate and the experiment was laid in Randomised Block Design. Application of 9 g N plant^–1 improved tree height by 15 to 25%, collar circumference by 30 to 37% and crown diameter by 18 to 26% in the initial 3 years. Total biomass increase due to 9 g N plant^–1 was 76% and 59%, respectively, after 1 and 2 years of planting. Application of 3 g P₂O₅ tree^–1 increased tree height by 8 to 18% and collar circumference by 17 to 24% during initial three years, and total biomass by 70% at 1 year and 30% at 2 years of age. Combined application of 18 g N and 3 g P₂O₅ tree^–1 (N₁₈P₃) was the best treatment which increased tree height by 49%, 85% and 35% and collar circumference by 56%, 10% and 11% at 1, 2, and 3 years of age, respectively. N₁₈P₃ treatment increased the total biomass by 181% at 1 year and 185% at 2 years of age. N and P applications improved considerably the branching of roots and root length and enhanced root biomass by 2 to 3 folds. N₁₈P₃ treatment increased the nitrogen uptake by 304% (4.02 g tree^–1) at 1 year and 211% (42.56 g tree^–1) at 2 years of age. The P uptake was maximum (290.4 mg tree^–1) due to N₁₈P₃ treatment in 1 year old and 11.37 g tree^–1 due to N₉P₆ treatment in 2 year old plantation.     

Influence of time and method of alfalfa stand termination on yield,seed quality,N uptake,soil properties and greenhouse gas emissions under different N fertility regimes

A field experiment was conducted in a 7-year old alfalfa stand to compare the influence of time and method of terminating alfalfa stands on crop yield, seed quality, N uptake and recovery of applied N for wheat (Triticum aestivum L.) and canola (Brassica napus L.), soil properties (ammonium-N, nitrate-N, bulk density, total and light fraction organic C and N), and N₂O emissions on a Gray Luvisol (Typic Cryoboralf) loam near Star City, Saskatchewan, Canada. The treatments were a 3 × 3 × 4 factorial combination of three termination methods [herbicide (H), tillage (T), and herbicide + tillage (HT)], three termination times (after cut 1 and cut 2 in 2003, and in spring 2004) and four rates of N (0, 40, 80 and 120 kg N ha⁻¹) applied at seeding to wheat-canola rotation from 2004 to 2007. In the termination year, soil nitrate-N was considerably higher in T or HT treatments than in the H treatment and decreased with delay in termination. In the first crop year, seed and straw yields of wheat grown on T and HT treatments were significantly greater than H alone (by 1,055–1,071 kg seed ha⁻¹ and by 869–929 kg straw ha⁻¹), due to greater content of soil available N in T treatments. Yields decreased with delay in termination time. In general, yield and N uptake in seed and straw, and protein concentration tended to increase with increasing N rate. A greater yield increase occurred on the H compared to T and HT treatments from the first increments of N applied. Nitrous oxide emissions were generally low and there were no treatment differences evident when cumulative 4-year N₂O-N losses were compared. Appropriate N fertilization was able to compensate for yield reductions due to delayed termination timing, but could not do so entirely for yield reductions on the H compared to T or HT termination method. The amounts of TOC, TON, LFOC and LFON after four growing seasons were usually higher or tended to be higher under H treatment than under T treatment in the 0–5 cm soil layer, but the opposite was true in the 5–10 cm or 10–15 cm soil layers.     

Long-term tillage,straw and N rate effects on some chemical properties in two contrasting soil types in Western Canada

Long-term use of soil, crop residue and fertilizer management practices may affect some soil properties, but the magnitude of change depends on soil type and climatic conditions. Two field experiments with barley, wheat, or canola in a rotation on Gray Luvisol (Typic Cryoboralf) loam at Breton and Black Chernozem (Albic Argicryoll) loam at Ellerslie, Alberta, Canada, were conducted to determine the effects of 19 or 27 years (from 1980 to 1998 or 2006 growing seasons) of tillage (zero tillage [ZT] and conventional tillage [CT]), straw management (straw removed [S_Rem] and straw retained [S_Ret]) and N fertilizer rate (0, 50 and 100 kg N ha^?1 in S_Ret, and 0 kg N ha^?1 in S_Rem plots) on pH, extractable P, ammonium-N and nitrate–N in the 0–7.5, 7.5–15, 15–30 and 30–40 cm or 0–15, 15–30, 30–60, 60–90 and 90–120 cm soil layers. The effects of tillage, crop residue management and N fertilization on these chemical properties were usually similar for both contrasting soil types. There was no effect of tillage and residue management on soil pH, but application of N fertilizer reduced pH significantly (by up to 0.5 units) in the top 15 cm soil layers. Extractable P in the 0–15 cm soil layer was higher or tended to be higher under ZT than CT, or with S_Ret than S_Rem in many cases, but it decreased significantly with N application (by 18.5 kg P ha^?1 in Gray Luvisol soil and 20.5 kg P ha^?1 in Black Chernozem soil in 2007). Residual nitrate–N (though quite low in the Gray Luvisol soil in 1998) increased with application of N (by 17.8 kg N ha^?1 in the 0–120 cm layer in Gray Luvisol soil and 23.8 kg N ha^?1 in 0–90 cm layer in Black Chernozem soil in 2007) and also indicated some downward movement in the soil profile up to 90 cm depth. There was generally no effect of any treatment on ammonium-N in soil. In conclusion, elimination of tillage and retention of straw increased but N fertilization decreased extractable P in the surface soil. Application of N fertilizer reduced pH in the surface soil, and showed accumulation and downward leaching of nitrate–N in the soil profile.     

Influence of organic amendments on growth, yield and quality of wheat and on soil properties during transition to organic production

A transition period of at least 2 years is required for annual crops before the produce may be certified as organically grown. The purpose of this study was to evaluate the effects of three organic amendments on the yield and quality of wheat (Triticum aestivum L.) and on soil properties during transition to organic production. The organic amendments were composted farmyard manure (FYMC), vermicompost and lantana (Lantana spp. L.) compost applied to soil at four application rates (60 kg N ha⁻¹, 90 kg N ha⁻¹, 120 kg N ha⁻¹ and 150 kg N ha⁻¹). The grain yield of wheat in all the treatments involving organic amendments was markedly lower (36–65% and 23–54% less in the first and second year of transition, respectively) than with the mineral fertilizer treatment. For the organic treatments applied at equivalent N rates, grain yield was higher for FYMC treatment, closely followed by vermicompost. In the first year of transition, protein content of wheat grain was higher (85.9 g kg⁻¹) for mineral fertilizer treatment, whereas, in the second year, there were no significant differences among the mineral fertilizer treatment and the highest application rate (150 kg N ha⁻¹) of three organic amendments. The grain P and K contents were, however, significantly higher for the treatments involving organic amendments than their mineral fertilizer counterpart in both years. Application of organic amendments, irrespective of source and rate, greatly lowered bulk density (1.14–1.25 Mg m⁻³) and enhanced pH (6.0–6.5) and oxidizable organic carbon (13–18.8 g kg⁻¹) of soil compared with mineral fertilizer treatment after a 2-year transition period. Mineral fertilized plots, however, had higher levels of available N and P than plots with organic amendments. All the treatments involving organic amendments, particularly at higher application rates, enhanced soil microbial activities of dehydrogenase, β-glucosidase, urease and phosphatase compared with the mineral fertilizer and unamended check treatments. We conclude that the application rate of 120 kg N ha⁻¹ and 150 kg N ha⁻¹ of all the three sources of organic amendments improved soil properties. There was, however, a 23–65% reduction in wheat yield during the 2 years of transition to organic production.     

Long-term effect of nutrient management and cropping system on cotton yield and soil fertility in rainfed vertisols

The effect of different N, P and K combinations with and without FYM on cotton productivity and the changes in soil fertility of three rainfed cotton based cropping systems were analyzed through a field experiment, conducted for 11 yr. Monoculture of G. arboreum (Asiatic) cotton, out-yielded monoculture of G. hirsutum (upland) cotton in 9 out of 11 yr. except in years of heavy rainfall. G. hirsutum cotton in rotation with sorghum produced 8% more yield than monocultured G. hirsutum. Significant responses to N and P application were consistently observed, while the response to K was inconsistent. Substituting half the N dose with FYM, gave 162 kg/ha and 222 kg/ha more seed cotton at low (N60 P13 K25) and high (N90 P20 K38) doses respectively. Also substituting half the N dose with FYM built up soil organic C from 4.2 to 5.4 g/kg, and increased available P from 4.5 to 6.4 mg/kg. The variations in the performance of the cropping systems and the response to fertilizers could not be accounted for by total rainfall alone. However, there was significant positive correlation between cotton yield and post September rainfall. Multiple regression equations were fitted to estimate G. arboreum and G. hirsutum yields based on the monthly distribution of rainfall.     

Effects of input level and crop diversity on soil nitrate-N,extractable P,aggregation, organic C and N,and nutrient balance in the Canadian Prairie

A field experiment was conducted from 1995 to 2006 on a Dark Brown Chernozem (Typic Boroll) loam soil at Scott, Saskatchewan, Canada to determine the influence of input level and crop diversity on accumulation and distribution of nitrate-N and extractable P in the soil profile, and soil pH, dry aggregation, organic C and N, and nutrient balance sheets in the second 6-year rotation cycle (2001–2006). Treatments were combinations of three input levels (organic input under conventional tillage—ORG; reduced input under no-till—RED; and high input under conventional tillage—HIGH), three crop diversities (fallow-based rotations with low crop diversity—LOW; diversified rotations using annual cereal, oilseed and pulse grain crops—DAG; and diversified rotations using annual grain and perennial forage crops—DAP), and six crop phases including green manure (GM), chem-fallow or tilled-fallow (F). Amount of nitrate-N in 0-240 cm soil was usually highest under the HIGH input-LOW crop diversity treatment and lowest under the ORG input-DAP crop diversity treatment. The distribution of nitrate-N in various soil depths suggested downward movement of nitrate-N up to 240 cm depth, especially with LOW crop diversity compared to DAP crop diversity, and with HIGH input. In some years, the ORG input systems had higher nitrate-N than the RED or HIGH input systems, which was attributed to low extractable P in soil for optimum crop growth and reduced nutrient uptake with ORG input management. Extractable P in soil was higher by a small margin for HIGH or RED input relative to ORG input in the 0–15 cm layer, suggesting little downward movement of P. Crop diversity did not affect extractable soil P due to the low baseline levels of P in this soil. The proportion of fine dry aggregates (<1.3 mm, erodible fraction) in 0–5 cm soil was highest with LOW crop diversity-HIGH input system, and lowest with DAG diversity-RED input system. The opposite was true for large aggregates (>12.7 mm). Wet aggregate stability was higher for RED input compared to ORG and HIGH input, which was attributed to the increase in the concentration of organic C in aggregates in the RED input system. Amount of light fraction organic matter (LFOM), light fraction organic C (LFOC) and light fraction organic N (LFON) in 0–15 cm soil was higher for RED input compared to ORG and HIGH inputs, and higher for DAG and DAP crop diversities than for LOW crop diversity. Soil N and P were usually deficient under ORG input management, but large amounts of N and P were unaccounted for, or in surplus, under RED and HIGH inputs, despite a marked increase in plant N and P uptake and crop yield compared to ORG input. Overall, our findings suggest that soil quality can be improved and nutrient accumulation in the soil profile can be minimized by increasing cropping frequency, reducing/eliminating tillage, and using appropriate combinations of fertilizer input and diversified cropping.     

Effect of the integrated use of legume residue,poultry manure and inorganic fertilizers on maize yield,nutrient uptake and soil properties

Identification of a sustainable integrated soil fertility management option in the tropics will not only salvage the degraded soils but also enhances the attainment of the goal of food security. This study was conducted in 2004 and 2005 on a degraded tropical Alfisol in south western Nigeria to evaluate the effect of legume residue, poultry manure and inorganic fertilizers on maize yield, nutrient uptake and soil properties. The treatments consisted of two rates of poultry manure (0 and 5 t ha⁻¹), three rates of N fertilizer (0, 50 and 100 kg N ha⁻¹ applied as urea), three rates of P fertilizer (0, 30 and 60 kg P ha⁻¹ applied as single super phosphate) and two soybean treatments (with or without incorporation of legume residue) in various combinations as a factorial experiment in Randomized Complete Block design with three replicates. Results showed that poultry manure alone led to significant increase in maize yield (60%) and soil organic matter (45%). In contrast, legume residue incorporation gave significantly lower increase in yield (7%) and soil organic matter (11%). However, the combined application of poultry manure and legume incorporation led to 72% increase in maize yield as opposed to 63 and 10% increase recorded when manure alone or legume alone were incorporated, respectively. Optimal maize yield was achieved when manure application was integrated with P fertilizer application. The interaction of P fertilizer and legume incorporation indicated that soil phosphorus and maize P concentration were significantly increased with the application of the P fertilizer and legume incorporation. Hence, the application of P fertilizer alone is most likely to be economical compared with its integration with legume incorporation.     

土壤条件和施肥对柑橘品质的影响

近年来,我国柑橘生产发展迅猛,产量连年增长,但品质不佳。为此,探讨了土壤条件和施肥对柑橘品质的影响,以期为优质柑橘的生产提供依据。     

施肥对土壤理化性状及玉米产量的影响

通过10年研究化肥与根茬、秸秆和有机肥定量配比施肥对土壤肥力、养分平衡及玉米产量的影响,结果表明:玉米单施化肥产量下降了7.9%;化肥 根茬产量持平;化肥 根茬 秸秆,土壤肥力和玉米产量同步上升,玉米增产17.1%;化肥 根茬 有机肥效果更佳,土壤肥力指标均上升,玉米增产32.1%。这对制定科学合理的培肥地力施肥措施,建立高产、优质、低耗的培肥制度,具有十分重要的意义。     

资源型功能磷肥对早稻产量、养分吸收及利用的影响

通过田间试验研究资源型功能磷肥对水稻产量、养分吸收及利用的影响。结果表明,与高浓度磷肥(HP)处理相比,两试验点3个资源型功能磷肥处理(LP1、LP2和LP3)平均增产8.3%和7.6%,磷肥吸收利用率平均提高29.4%和20.7%。资源型功能磷肥不仅能显著增产,还能显著促进磷的吸收及利用,应该大力推广施用。     

Effect of green manure on the yield,N uptake and floodwater properties of a flooded rice,wheat rotation receiving15N urea on a highly permeable soil

Field studies were conducted for two years on a rapidly percolating loamy sand (Typic Ustochrept) to evaluate the effect of green manure (GM) on the yield,¹⁵N recovery from urea applied to flooded rice, the potential for ammonia loss and uptake of residual fertilizer N by succeeding crops. The GM crop ofSesbania aculeata was grownin situ and incorporated one day before transplanting rice. Urea was broadcast in 0.05 m deep floodwater, and incorporated with a harrow. Green manure significantly increased the yield and N uptake by rice and substituted for a minimum of 60 kg fertilizer N ha^–1. The recovery of fertilizer N as indicated by¹⁵N recovery was higher in the GM + urea treatments. The grain yield and N uptake by succeeding wheat in the rotation was slightly higher with GM. The recovery of residual fertilizer N as indicated by the¹⁵N recovery in the second, third and fourth crops of wheat, rice and wheat was only 3, 1 and 1 per cent of the urea fertilizer applied to the preceding rice crop. Floodwater chemistry parameters showed that the combined use of the GM and 40 kg N ha^–1 as urea applied at transplanting resulted in a comparatively higher potential for NH₃ loss immediately after fertilizer application. The actual ammonia loss as suggested by the¹⁵N recoveries in the rice crop, however, did not appear to be appreciably larger in the GM treatment. It appeared the ammonia loss was restricted by low ammoniacal-N concentration maintained in the floodwater after 2 to 3 days of fertilizer application.     

Effect of different sources of iron and sulphur on leaf chlorosis,nutrient uptake and yield of groundnut

The pot experiment conducted in calcareous soil of Saurashtra, India showed that application of lime (20% CaCO₃) and excess water (irrigation at –0.3 bar) to the soil enhanced chlorosis in groundnut leaves caused by induced deficiencies of iron, sulphur and zinc, which was recovered by applying agricultural grade chemicals containing iron, sulphur and zinc. This chlorosis caused 29.8 and 19.1% reduction in pod yield of groundnut due to lime and excess water, respectively in the untreated control pot and 17.1 and 9.6%, respectively in the pot treated with different chemicals.Application of iron sulphate, zinc sulphate, iron pyrite, gypsum, phospho-gypsum, elemental sulphur, wettable sulphur and Fe-EDTA decreased chlorosis and increased chlorophyll and carotenoid contents of leaves, uptake of Fe, S and Zn and pod yield of groundnut significantly. The foliar spray of 0.5% aqueous solution of iron sulphate, zinc sulphate and Fe-EDTA at 20, 35, 50 and 65 days after emergence (DAE) was more effective than their soil applications. The Fe-EDTA corrected only iron chlorosis, and gypsum, phosphogypsum and elemental sulphur only sulphur chlorosis. However, iron sulphate and iron pyrite corrected iron and sulphur and zinc sulphate corrected zinc and sulphur chlorosis. Among the soil amendments, application of iron sulphate and iron pyrite showed better responses to groundnut and showed higher Fe and S uptake than other treatments. The responses of gypsum, phosphogypsum and elemental sulphur were at par. The correlation study showed that pod yield of groundnut was negatively correlated with chlorosis and positively correlated with the chlorophyll and carotenoid contents in groundnut leaves.