Phosphorus skipping effect on productivity,profitability and sustainability of rice-wheat cropping systems in Indo-Gangetic plains of India

A field experiment was conducted for eight years at ICAR-Indian Institute of Wheat and Barley Research, Karnal, Haryana, India to study the skipping effect of P application on productivity, profitability and sustainability of rice-wheat cropping system. Rice yield and biomass were 8.35% and 6.6% higher where cowpea was grown after wheat compared to rice-vegetable pea-wheat crop sequence, respectively. Phosphorus application to rice or wheat or both crops exhibited at par rice grain yield, biomass, harvest index. Phosphorus application to both crops or only in rice crop produced maximum and significantly higher wheat yield (4.62 t ha^?1) as compared to P application only to wheat (4.48 t ha^?1). Eight years growing of green gram, cowpea and vegetable pea increased the organic carbon content 42.89, 16.38 and 4.57 %, respectively compared to the initial level. Skipping of P to either crop, by considering 13.5 million ha rice-wheat area, will save approximately Rs 40,500 million (Rs = Indian rupee) or US $ 623 million ($ = Rs 65) per year. Air pollution may be checked, due to saving on diesel in transportation of P fertilizer, to the tune of 60,383 tonnes of CO₂ per year by reducing emission of one of important global warming gas.     

Long-term yield trend and sustainability of rainfed soybean–wheat system through farmyard manure application in a sandy loam soil of the Indian Himalayas

A long-term (30 years) soybean–wheat experiment was conducted at Hawalbagh, Almora, India to study the effects of organic and inorganic sources of nutrients on grain yield trends of rainfed soybean (Glycine max)–wheat (Triticum aestivum) system and nutrient status (soil C, N, P and K) in a sandy loam soil (Typic Haplaquept). The unfertilized plot supported 0.56 Mg ha⁻¹ of soybean yield and 0.71 Mg ha⁻¹ of wheat yield (average yield of 30 years). Soybean responded to inorganic NPK application and the yield increased significantly to 0.87 Mg ha⁻¹ with NPK. Maximum yields of soybean (2.84 Mg ha⁻¹) and residual wheat (1.88 Mg ha⁻¹) were obtained in the plots under NPK + farmyard manure (FYM) treatment, which were significantly higher than yields observed under other treatments. Soybean yields in the plots under the unfertilized and the inorganic fertilizer treatments decreased with time, whereas yields increased significantly in the plots under N + FYM and NPK + FYM treatments. At the end of 30 years, total soil organic C (SOC) and total N concentrations increased in all the treatments. Soils under NPK + FYM-treated plots contained higher SOC and total N by 89 and 58% in the 0–45 cm soil layer, respectively, over that of the initial status. Hence, the decline in yields might be due to decline in available P and K status of soil. Combined use of NPK and FYM increased SOC, oxidizable SOC, total N, total P, Olsen P, and ammonium acetate exchangeable K by 37.8, 42.0, 20.8, 30.2, 25.0, and 52.7%, respectively, at 0–45 cm soil layer compared to application of NPK through inorganic fertilizers. However, the soil profiles under all the treatments had a net loss of nonexchangeable K, ranging from 172 kg ha⁻¹ under treatment NK to a maximum of 960 kg ha⁻¹ under NPK + FYM after 30 years of cropping. Depletion of available P and K might have contributed to the soybean yield decline in treatments where manure was not applied. The study also showed that although the combined NPK and FYM application sustained long-term productivity of the soybean–wheat system, increased K input is required to maintain soil nonexchangeable K level.     

Long-term productivity growth and sustainability of Greek irrigated agriculture

The present study examines the long-term productivity growth and sustainability of Greek irrigated agriculture. A log linear trend model was used to measure long-term productivity growth, and the total factor productivity (TFP) approach measures the sustainability of the irrigated production system. A time series database of inputs and outputs data were used for the production period of 1961?–?2001 (41 years) which revealed that there is an increasing trend in the irrigated area of the country. The annual growth rate of the irrigated area is 2.6% during this time period. The long-term trends in yields of crops grown in irrigated agriculture are positive. Fertilizer use rate per ha sharply increases during this period. The productivity of irrigated Greek agriculture also increases over the time period as a result of the introduction of High Yielding Variety (HYV), seed, fertilizer and water technology. The measurement of TFP indices indicates that the long-term trend in productivity growth of irrigated Greek agricultural system is positive. The result implies that the irrigated Greek agricultural production system has long-term sustainability. The result also indicates that fertilizer, fixed capital, rainfall and temperature are positively contributing to the mean production of Greek irrigated agriculture. On the other hand, pesticide, labour and fixed capital reduces variability of irrigated agriculture. To this end, long-term agricultural sustainability depends on patterns of input use.     

Effect of long-term application of rice straw,farmyard manure and inorganic fertilizer on potassium dynamics in soil

Knowledge of K-dynamics in soils can help devise practices for efficient K management in intensive rice-wheat systems. We studied the effect of long-term application of rice straw, farmyard manure (FYM) and inorganic fertilizer on total K and its distribution among different forms in 60-cm soil profile after 14 years of rice-wheat cropping. The exchangeable, the non-exchangeable and the lattice K respectively comprised 1%, 3–10% and 89–95% of total K in surface soil under different treatments. Application of rice straw and FYM positively impacted total K status of soil and its distribution among different forms. The greatest concentrations of total K, lattice K, exchangeable K and NH₄OAc-extractable K were observed in plots receiving both rice straw and FYM together and the lowest in inorganic fertilizer treated plots. On the contrary, the non-exchangeable K was the highest in inorganically fertilized plots and the lowest in rice straw amended plots. The exchangeable, the water soluble and the NH₄OAc-extractable K decreased with soil depth and did not indicate K movement beyond the rooting zone of the crops. The results showed that incorporation of rice residue in soil, instead of burning, besides reducing environmental pollution led to improved K-fertility of soils.     

System of rice intensification in promising rice hybrids in north-western Himalayas: crop and water productivity,quality, and economic profitability

System of Rice Intensification (SRI) has spread as an innovation of rice cultivation that can produce higher crop yields and conserve seed and water resources. The SRI innovation is also gaining popularity in north-western (NW) Himalayas on one hand and hybrid rice technology on the other in the region. Moreover, rice productivity in NW Himalayas is quite low owing to the use of low-yielding germplasm and poor crop management. Thus, SRI principles coupled with hybrid rice technology seems to be a boon to boost rice productivity in the irrigated ecosystem of wet-temperate NW Himalayas well known for rice cultivation. Therefore, comparative performance of promising rice hybrids under SRI was assessed at three locations in wet-temperate NW Himalayas (India) using nine promising rice hybrids including state-recommended rice hybrid “Arize–6129” as check cultivar. It was revealed that various hybrids differed significantly w.r.t. days to 50% flowering, days to 75% maturity, plant height, tillers hill^?1, panicles hill^?1, panicles m^?2, and panicle length. Highest number of panicles m^?2 (370) was observed in Arize–6129 followed by US–312, Bioseed–786, and NK–3325, respectively. Significantly longer panicles were observed in Dhanya–2366 followed by Arize–6129, US–312, Bioseed–786, NK–3325, and US–10, respectively. Arize–6129 resulted in significantly higher grain (75 q ha^?1) and straw yield (125 q ha^?1) followed by US–312, Dhanya–2366, NK–3325, PAC–801, US–10, Bioseed–786, Uday–111, and Uday–131, respectively. The production- and monetary-efficiency as well as gross and net returns and B:C ratio also followed the similar trend as that of crop productivity with significantly higher production– (67 kg ha^?1 day^?1) and monetary–efficiency (INR 608.4 ha^?1 day^?1), and net returns (INR 68138 ha^?1) and B:C ratio (3.66) in check cultivar “Arize–6129” over other rice hybrids. Higher grain productivity (49.5–75.0 q ha^?1), net returns (INR 39238–68138 ha^?1), and B:C ratio (2.53–3.66) in current study conclusively inferred that SRI coupled with hybrid rice technology can harness higher productivity and profitability. Protein content (8.30–8.45%) exhibited higher values under Bioseed–786 followed by NK–3325, UDAY–111, and Arize–6129; however, NPK uptake (grains, straw, total) was significantly highest in Arize–6129 followed by US–312, Dhanya–2366, and NK–3325, respectively. Total water productivity (6.4–9.75 kg ha^?1 mm^?1), irrigation water productivity (16.5–25 kg ha^?1 mm^?1), and economic water productivity (64.0–97.5 INR ha^?1 mm^?1) collectively followed the trend of Arize–6129 > US–312 > Dhanya–2366 > NK–3325 > US–10 > PAC–801 > Bioseed–786 > Uday–111 > Uday–131 in current study. Overall, Arize–6129, US–312, and Dhanya–2366 were proved as potential rice hybrids in terms of their higher crop and water productivity and economic profitability among above nine rice hybrids for their large-scale cultivation under SRI in wet-temperate NW Himalayas.     

Nutrient management and submergence-tolerant varieties antecedently enhances the productivity and profitability of rice in flood-prone regions

Abstract

Poor productivity of rice in rainfed lowlands is due to complete submergence as it is a major abiotic stress of these regions. For enhancing the rice productivity of these areas, better nutrient management options are required and results may even better when combined with stress tolerant cultivars, even when tested under natural conditions of farmers’ field. For supporting the above statement, the effect of nitrogen and phosphorus in graded doses was evaluated for submergence tolerance in controlled conditions and the results obtained were tested and validated at farmers’ field in Cuttack, Odisha, India. Shoot elongation, leaf senescence and lodging were lowest with the application of higher phosphorus (60?kg ha^?1). Highest dose i.e. 100-60-40 NPK kg ha^?1 resulted in higher plant survival of all the varieties by 90–170% over no nutrient application, it was also reflected in the higher growth after recovery, leaf greenness, leaf and stem growth, chlorophyll and carbohydrate concentrations and ultimately higher grain yield. At farmers’ field, application of basal P, K and post-flood N management practice resulted in overall better performance of Swarna and Swarna-Sub1 showing higher yield attributes leading to 65.7 and 37.9% higher grain yield, over conventional practices followed by farmers. Apart from that results were more positive if post-flood nitrogen was applied as urea foliar spray might be due to quick absorption of N by plant leaves and also spraying helps in removing the silt of flood water sticking to the leaf surface and facilitated the plants to photosynthesize and survive after desubmergence. These cost-effective management options may enhance the productivity and profitability of rice in the flood-prone areas where farmers hesitate to apply nutrients.     

Long-term effects of straw and farmyard manure on crop yields and soil properties

The effect of cereal straw with added mineral N fertilization on crop yields, N uptake, total organic C content and hot water soluble C content in topsoil and on the relationships between organic C content in topsoil and organic matter balance was evaluated in a long-term field experiment established in 1966. The effect of straw plus mineral N fertilization was similar to the effect of farmyard manure (FYM) in the dry matter yields and also in the N uptake by plants. The effect of straw and mineral N fertilization on the organic C accumulation in soil was inferior to the effect of farmyard manure. Relationships between organic matter balance and total organic C content in the topsoil was positive and statistically significant. A favourable effect of mineral NPK fertilization on the C sequestration to soil was related to the effect of FYM fertilization.     

Long-term effects of farmyard manure and sewage sludge on some soil biochemical characteristics

 Changes in some soil biochemical properties were investigated following repeated applications of aerobically digested sewage sludge (SS) under field conditions over 12 years, and compared with those of an adjacent soil cultivated and amended with 5 t ha^–1 year^–1 (dry weight) farmyard manure (FYM) for at least 40 years, as well as with those of an adjacent uncultivated soil, in order to ascertain changes in soil quality. A short-term aerobic incubation was used to determine the potential of the samples to mineralize the organic C supplied. Results indicated that cultivation caused a reduction in total, humified and potentially mineralizable organic C, total N, light-fraction (LF) C, total and water-soluble carbohydrates, phenolic compounds, cation-exchange capacity (CEC), microbial biomass C, specific respiration, hydrolytic and urease activities, and an increase in the heavy metal content. Total and water-soluble carbohydrates and phenolic compounds expressed as a percentage of total organic C (TOC) were similar in the differently managed plots. Of the two amendments, FYM treatments showed higher amounts of TOC and N, LF-C, total and water-soluble carbohydrates, phenolic substances, CEC, specific respiration of biomass, hydrolytic and urease activities, similar amounts and characteristics of humified organic matter and lower concentrations of Cu, Zn and Cr. Both FYM and SS were inadequate treatments for the restoration of soil organic matter lost as a consequence of cultivation. Received: 20 October 1998     

Effect of lime water – manure organic fertilizers on the productivity,energy efficiency and profitability of rainfed maize production

ABSTRACT

Agro-industrial activities such as livestock production and maize processing generate large amounts of waste that can pollute the environment if not treated. To reduce the environmental impact of such wastes, the use of nejayote and ovine manure as fertilizers in maize production was evaluated in terms of yield (GY), energy efficiency (EE) and benefit-to-cost ratio (BCR), during 2015 and 2016. A factorial experiment was designed combining nejayote (0, 75 and 150 m³ ha^?1) with manure (0, 25 and 50 Mg ha^?1), those treatments were compared with a chemical fertilizer treatment (120N–60P–30K); treatments were done in three replicates. Nejayote-manure fertilizers were characterized physical and chemically. Inputs and outputs used/obtained during the production cycle were registered in terms of their energy equivalents and economic value. At the end of each cycle GY, EE and BCR were calculated. Results showed that nejayote-manure mixtures were 19% more energy efficient and produced a yield 12% greater than chemical fertilization (P = 0.001), thus generating a BCR of 6.3 (P = 0.023). Organic fertilizers were useful as waste treatments and produced greater benefits than chemical fertilizers. Additionally, the water recovered from nejayote was enough to provide a 7.5 or 15 mm of gross irrigation during the crop cycle.     

Effects of farmyard manure and inorganic fertilizer on the dynamics of soil microbial biomass in a tropical dryland agroecosystem

Changes in the soil microbial biomass following applications of farmyard manure and inorganic fertilizer, alone and in combination, were studied for two annual cycles in a rice-lentil crop sequence grown under rainfed tropical dryland conditions. During the two annual cycles the microbial biomass C range (g g^-1) was 146–241 (x = 204), 191–301 (245), 244–382 (305), and 294–440 (365) in control, fertilizer, manure and manure+fertilizer plots, respectively. The corresponding ranges for microbial biomass N (g g^-1) were 16.5–21.0 (19.5), 20.4–38.2 (26.0), 23.0–34.6 (27.0) and 26.2–42.4 (33.3), and for microbial biomass P (g g^-1) 4.4–8.2 (7.0) 6.0–11.2 (9.6), 11.2–22.0 (17.0), and 10.0–25.4 (18.3). The maximum increase in the microbial biomass, due to these inputs was observed under the manure+fertilizer treatment followed, in decreasing order, by manure alone and fertilizer alone. Within individual crop periods the levels of microbial biomass decreased sharply from the seedling to the flowering stage and then increased slightly with crop maturity. The maximum levels of microbial biomass C and P were observed during the summer fallow. The maximum accumulation of microbial biomass N occurred in the early rainy season, immediately after the soil amendments. Microbial biomass C, N, and P were positively related to each other throughout the annual cycle.     

Effect of continuous application of farmyard manure and inorganic fertilizer for 9 years on changes in phosphorus compounds in plow layer of an upland Andosol

The changes in total phosphorus (P) accumulation in the plow layer and in the contents of several P compounds in an upland Andosol with time and the effects of these changes on biomass production at the field level were investigated in relation to the continuous application of farmyard manure and compost (referred to as “farmyard manure”) and inorganic P for 9 y. 1) Inorganic P applied continuously without farmyard manure accumulated only in the plow layer of the upland Andosol, whereas the combined application of inorganic P and farmyard manure P led to the leaching below the plow layer, with a constant level (3.3–3.5 g kg^-1) of P accumulation in the plow layer within several decades. In order to reach a constant P accumulation level, higher application of P shortened the time required for the accumulation. 2) Bray No. 2-P value in the plow layer increased with time and tended to become maximum only under the application of both inorganic P and farmyard manure. 3) Aluminum (AI) bound-P (AI-P) fraction in the plow layer of the Andosol increased continuously and quadratically with the cultivation, along with an accelerated decrease in the amount of iron bound-P (Fe-P) and residual-P fractions (Res-P) during the 9-y period. 4) Continuous application of farmyard manure accelerated the decrease in the organic P (Org-P) fraction, presumably due to promoting microbial activity in the plow layer. 5) During the 9-y period, differences in crop growth with and without continuous application of P became attenuated, suggesting that the availability of accumulated P in the plow layer of the Andosol farm field before the experiment increased for the subsequent crop cultivation. Continuous increase in the AI-P fraction with time was closely correlated with the increase in P availability of accumulated P for crop growth.     

Long-term effects of metal-containing farmyard manure and sewage sludge on soil organic matter in a fluvisol

Our aim was to establish the long-term effects of repeated applications after 20 y of organic amendments (farmyard manure at 10 t ha⁻¹ y⁻¹, and urban sewage sludge at two different rates, 10 t ha⁻¹ y⁻¹ and 100 t ha⁻¹ every 2 y) on the quality of a sandy and poorly buffered soil (Fluvisol, pH 6). Chemical characteristics and biodegradability of the labile organic matter, which is mainly derived from microbial biomass and biodegradation products of organic residues, were chosen as indicators for soil quality. The organic C content had reached a maximal value (30.6 g C kg⁻¹ in the 100 t sludge-treated soil), i.e. about 2.5 times that in the control. Six years after the last application, the organic C content and the microbial biomass content remained higher in sludge-treated soils than in the control. In contrast, the proportion of labile organic matter was significantly lower in sludge-treated soils than in manure-treated and control soils. The labile organic matter of sludge extracts appeared less humified than that of manure-treated and control soils.     

Management influence on maize–wheat system performance,water productivity and soil biology

Cereal cropping productivity in the Indo‐Gangetic Plain (IGP) of India is declining, which may be overcome by diversification, alternate crop establishment methods and mulching. This study was conducted to determine whether no‐till flat (NTF), permanent raised beds (PRB) and nontraditional ex situ mulching would improve crop and water productivity, economic profitability and soil biological properties in an irrigated maize (Zea mays)–wheat (Triticum aestivum) system (MWS). NTF systems produced 10% higher economic net returns compared with PRBs. Non‐traditional mulching (Sesbania, Jatropha and Brassica) increased yields by >10% and net returns by >12% compared with no‐mulch. The water saving in PRBs compared with NTF systems was 79, 94 and 173 mm/ha in maize, wheat and MWS, respectively. PRBs saved 29.2% of irrigation water and improved the MWS irrigation water productivity (WP_I) by 24.5% over NTF. On average, mulching saved 23.8 mm/ha irrigation water over no‐mulch and improved WP_I by 12.0%. PRBs with ex situ mulching produced wheat and maize equivalent system yields lower than NTF but improved WP_I and soil biological properties. Jatropha and Sesbania mulching improved yield, water saving, WP_I and system profitability. In limited irrigation and no crop residue availability conditions, Sesbania, Jatropha and Brassica vegetation material have potential applications for ex situ mulching under PRBs for water saving and NTF for productivity.     

Conservation agriculture based sustainable intensification of basmati rice-wheat system in North-West India

Continuous mono-cropping of rice-wheat (RW) system with conventional tillage (CT) based management practices have led to decline in soil health, groundwater table and farmers profit in north-west India. A medium-term (4 years) farmer’s participatory strategic research trial of basmati RW system was conducted to evaluate the effects of conservation agriculture (CA) based management practices on crop yields, water productivity, profitability and soil quality. Six treatments were compared varied in the cropping system, tillage, crop establishment and residue management. CA-based management under zero-till direct seeded rice-wheat-mungbean recorded 36% higher system yield than conventional till rice-wheat system (14.91 Mg ha^?1). CA-based rice-wheat system and rice-wheat-mungbean system saved ~35% irrigation water compared to conventional RW system (2168 mm ha^?1). Total water productivity (WP_I+R) was improved by 67% with CA-based rice-wheat-mungbean system (0.90 kg grain m^?3) over the conventional system. On system basis, 42% higher net return was recorded with CA-based rice-wheat-mungbean system compared to conventional system (USD 2570 ha^?1). Mungbean integration in basmati RW system contributed 29% share in system net returns across the treatments. Soil chemical and biological properties were improved by ~40% and 150%, respectively, with CA-based management system.     

Changes in an Alfisol under long-term application of manure and inorganic fertilizer

Abstract. Changes in surface soil properties of a savanna Alfisol under cultivation with applications of manure and inorganic NPK fertilizer were evaluated after 45 years of annual cropping. Soils from treatments with fertilizer only, fertilizer in combination with farmyard manure (FYM) at both high and low rates were compared to soil from a control receiving neither fertilizer nor manure. The high rate of FYM and fertilizer significantly improved soil aggregation, increased C, N and P status, while reducing soil penetration resistance. The results showed that there is a need to use both manure and inorganic fertilizer to maintain soil fertility in savanna soils under continuous cultivation.     

Long-term inorganic fertilizer use influences bacterial communities in Mollisols of Northeast China based on high-throughput sequencing and network analyses

The effects of chemical fertilizers on soil microbial communities have been well studied in a variety of terrestrial systems. However, the individual effects of N, P, and K fertilizers and their combinations (NP, NK, PK and NPK) on bacterial community structure in black soils have not been fully understood. In this study, we applied Illumina MiSeq sequencing and network analysis targeting 16S rRNA gene to comprehensively characterize the effects of 35 years of these inorganic fertilizers on community diversity and composition in the black soil. The results of α-diversity indices and principal coordinates analysis (PCoA) indicated that the N-addition treatments had larger effects than the others. The network analysis showed that the N fertilizer shifted the network structure, topological roles of individual OTUs and key bacterial populations, contributing to a simple network under the N-fertilizer treatments compared with non-N fertilizers treatments. These findings suggested that N fertilizer reduced the bacterial diversity and simplified the interactions among key bacterial members in Mollisol. The results of this study could provide basis for further researches balancing different N application levels, the bacterial community network and crop yield to maintain the ecosystem function and stability.

Abbreviations: N: nitrogen fertilizer; P: phosphorus fertilizer; K: potassium fertilizer; NP: nitrogen and phosphorus fertilizers; NK: nitrogen and potassium fertilizers; PK: phosphorus and potassium fertilizers; NPK: phosphorus and potassium fertilizers; TC: total carbon; TN: total nitrogen; TP: total phosphorus; TK: total potassium; AP: available phosphorus; AK: available potassium; OTUs: operational taxonomic Units; ACE: abundance-based coverage estimator; Chao1: estimated OTU richness; PCoA: principal coordinates analysis     

Sustainable productivity and profitability of diversified rice-based cropping systems in an irrigated ecosystem

An experiment was conducted at ICAR Research Complex for Eastern Region, Research Farm, Sabajpura, Patna (longitude 85°13′N and 1atitude 25°37′E), Bihar, India for four consecutive years 2004–05 to 2007–08 to develop a diversified cropping system for an irrigated ecosystem in Bihar by introducing pulse/oilseed/vegetables as a second or third crop in 10 rice-based cropping systems. Four crop cycles have been completed for all the cropping systems. During all years of the experiment there were significant variations among the cropping systems. Maximum paddy yield equivalent was recorded in rice–tomato–bottle gourd (40.44 t ha^?1) followed by rice–potato–onion (28.47 t ha^?1), rice–coriander–lady's fingers (26.79 t ha^?1), rice–carrot–cowpea (24.59 t ha^?1) and rice–mustard–tomato (24.44 t ha^?1). A higher value for the diversification index (DI) represents a higher level of crop diversification. It is evident from the results, that DI varies from 0.299 on a medium-sized farm to 0.903 on a small farm, with an average DI value of 0.643 among all farm categories. A survey revealed that the average DI value for small-scale farmers was highest (0.741) compared with the medium- (0.591) and large-scale (0.626) categories, and the differences were negligible. This seems reinforce the view that the smaller the farm, the higher the level of crop diversification.     

水稻-小麦轮作系统中土壤活性有机碳库对长期施用化肥，秸秆和粪便的敏感度

Labile soil organic carbon(SOC) pools, estimated through chemical fractionation techniques, are considered sensitive indicators of management-induced changes in quality and composition of soil organic matter. Although the impacts of organic manure and crop residue applications on C sequestration in rice-wheat system are fairly well documented, their influence on labile SOC pools is relatively less known. Impacts of organic manure, rice straw, and inorganic fertilizer nitrogen(N) applications on soil total organic carbon(TOC)and SOC pools including water-extractable organic C(WEOC), hot water-soluble organic C(HWOC), potassium permanganateoxidizable organic C(KMnO 4-C), microbial biomass C(MBC), mineralizable organic C(Cmin), and the oxidizable fractions of decreasing oxidizability(easily-oxidizable, oxidizable, and weakly-oxidizable) were investigated in an 11-year field experiment under rice-wheat system. The field experiment included treatments of different combinations of farmyard manure, rice straw, and fertilizer N application rates, with C inputs estimated to be in the range from 23 to 127 Mg ha-1. After 11 years of experiment, WEOC,HWOC, and KMnO 4-C were 0.32%–0.50%, 2.2%–3.3%, and 15.0%–20.6% of TOC, respectively. The easily-oxidizable, oxidizable,and weakly-oxidizable fractions were 43%–57%, 22%–27%, and 10%–19% of TOC, respectively. The applications of farmyard manure and rice straw improved WEOC, HWOC, KMnO 4-C, easily-oxidizable fraction, Cmin, and MBC, though the rates of change varied considerably from-14% to 145% and-11% to 83% of TOC, respectively. At the C input levels between 29 and 78 Mg C ha-1during the 11-year period, the greatest increase was observed in WEOC and the minimum in KMnO 4-C. Water-extractable organic C exhibited a relatively greater sensitivity to management than TOC, suggesting that it may be used as a sensitive indicator of management-induced changes in soil organic matter under rice-wheat system. All the other labile SOC pools exhibited almost the same sensitivity to management as TOC. Most of the SOC pools investigated were positively correlated to each other though their amounts differed considerably. Long-term applications of farmyard manure and rice straw resulted in build-up of not only the labile but also the recalcitrant pool of SOC, emphasizing the need for continued application of organic amendments for permanence of the accrued C under the experimental conditions.     

Long-term farmyard manure application effects on properties of a silty clay loam soil under irrigated wheat–soybean rotation

Increasing importance has been placed on the use of agricultural soils for the mitigation of atmospheric CO₂ through sequestration of soil C. Although crop productivity is sustained mainly through the application of organic manure in the Indian Himalayas, little information is available on C sequestration, C content in different aggregate size fractions and soil water transmission properties (infiltration and saturated hydraulic conductivity) as affected by long-term manure addition. We analyzed results of an 8-year experiment, initiated in 1995–1996 on a silty clay loam soil, to determine the influence of fertilizer and fertilizer + farmyard manure (FYM) application on those important soil properties. The overall increase in soil organic C (SOC) content in the 0–45 cm soil depth in NPK + FYM treatment as compared to NPK and control treatments was 11.0 and 13.9 Mg C ha⁻¹ at the end of 8 years, respectively. Application of FYM significantly reduced soil bulk density and increased mean weight diameter (MWD) and SOC contents in different aggregate size fractions. Soil organic C content in macroaggregates was greater than in microaggregates. The response of SOC content to FYM application was dependent upon inorganic fertilization and more upon balanced application of NPK than N only. Steady state infiltration rate under NPK + FYM (1.98 cm h⁻¹) was higher than under unfertilized (0.72 cm h⁻¹) and NPK (1.2 cm h⁻¹). Soil water sorptivity (calculated from Philip's equation) under NPK + FYM (1.06 cm min^−0.5) was higher than under NPK (0.61 cm min^−0.5). We conclude that hill farmers in northern India should be encouraged to use FYM along with chemical fertilizers to increase SOC content and improve soil physical properties.     

农业系统可持续度的随机模拟方法与实证分析

从系统学角度,对农业可持续发展的持续度的确定问题进行了定量化分析。首先利用功效函数评价和时间序列的随机模拟分析等方法,建立了农业可持续发展系统的持续度理论计算模型与模拟预测模型;在此基础上,对浙江省农业系统可持续性的定量化确定及模拟预测问题进行了实证分析。研究结果表明,文中提出的计算模型能比较好的适应农业系统随机不确定性等基本特征,实证研究结论也为浙江省进一步实施农业可持续发展战略提供有益的决策参考。