Anand Swarup

Do organic amendments improve yield trends and profitability in intensive rice systems

Opinions differ as to the importance of organic amendments (OA) for sustaining crop productivity in the intensive, irrigated rice systems of Asia. Our objectives were to (1) quantify the effects of farmyard manure (FYM) and straw incorporation on yield trends in long-term experiments (LTEs) with rice–rice (R–R) (Oryza sativa L.) and rice–wheat (R–W) (Triticum aestivum L.) systems and (2) assess the potential effects of OA on profitability, taking into account long-term effects on yield. We analyzed yield trends in 25 LTE (seven R–R, 18 R–W systems) across a wide geographical range in Asia. Three main conclusions emerged from this analysis. First, application of either manure or straw did not improve grain yield trends in R–R and R–W cropping systems. Second, depending on socio-economic conditions, use of manure or straw in these cropping systems may be profitable, provided these OA are used as a complement to a recommended dose of inorganic NPK (i.e. organic materials should not be used as the primary nutrient source). Third, current experimental designs to assess the suitability of OA need to be improved in order to allow a better comparison of the relative advantages of inorganic and organic fertilizers. The major shortcoming of current designs is that they do not properly adjust mineral fertilizer rates in the inorganic treatments to account for the macronutrient input from OA. Thus, our tentative estimates of the profitability of OA may be overstated.

Long-term continuous cropping, fertilisation, and manuring effects on physical properties and organic carbon content of a sandy loam soil

Effects of continuous cropping, fertilisation, and manuring on soil organic carbon content and physical properties such as particle size distribution, bulk density, aggregation, porosity, and water retention characteristics of a Typic Ustochrept were examined after 31 cycles of maize–wheat–cowpea (fodder) crop rotation. Five contrasting nutrient treatments from a long-term fertiliser experiment were chosen for this study: control (no fertiliser or manure); 100% (optimum dose) nitrogen (N) fertiliser; 100% nitrogen and phosphorus (NP); 100% nitrogen, phosphorus, and potassium (NPK); 100% NPK + farmyard manure (NPK+FYM). The NPK+FYM treatment significantly improved soil organic carbon (SOC) content in 0–0.15 m soil compared with the other 4 treatments; the NPK treatment resulted in significantly more SOC than the control and N treatments (P < 0.05). The SOC in NPK and NPK+FYM treatments was 38.6 and 63.6%, respectively, more than the initial level of SOC (4.4 g/kg) after 31 cycles of cropping. The control and N treatments maintained the SOC status of the soil at the initial value. NPK+FYM significantly improved soil aggregation, soil water retention, microporosity, and available water capacity and reduced bulk density of the soil at 0–0.30 m depth. Greater crop growth under the NPK treatment resulted in increased organic matter content of soil, which improved aggregate stability, water retention capacity, and microporosity compared with the control. The effects were more conspicuous with the NPK+FYM treatment and at the surface soil (0–0.15 m). Application of imbalanced inorganic fertiliser (N and NP treatments) did not have a deleterious effect on the physical properties of the soil compared with the control. SOC content showed a highly significant and positive correlation with mean weight diameter (0.60), % water-stable macro-aggregates (0.61), and soil water retention at –0.033 MPa (0.75) and –1.5 MPa (0.72), and negative correlation with bulk density (–0.70) for the surface 0–0.15 m soil. The study thus suggests that application of balanced mineral fertilisers in combination with organic manure sustains a better soil physical environment and higher crop productivity under intensive cultivation.

Effects of short-term flooding on growth, yield and mineral composition of wheat on sodic soil under field conditions

In sodic soils of the Indo-Gangetic alluvial plains of Northern India, flooding for short periods often occurs during the growing season of wheat, leading to low yields. A field study was therefore conducted to evaluate the effects of short-term flooding on growth, yield and mineral composition of wheat (Triticum aestivum Linn. emend. Fiori and Paol) in a sodic soil (pH 8.9, exchangeable sodium percentage 25). Flooding wheat for 2,4 and 6 days at the time of first irrigation (25-day old plants), significantly reduced tillering, plant height, delayed head emergence and resulted in 17.6, 29.0 and 46.7% reduction in grain yield, respectively, Flooding decreased oxygen diffusion rate (ODR) values, restricted root grwoth and reduced ion uptake, especially of N, P, K, Ca, Mg and Zn and led to higher absorption of Na, Fe and Mn. Under the conditions of this experiment, the reduced growth and yield of wheat resulting from short-term flooding was not due to Mn, Fe and Na toxicity but may be due to reduced uptake of nutrients resulting from O2 deficiency in the soil.

Long-term effects of NPK fertiliser and manure on soil fertility and a sorghum–wheat farming system

Yield decline or stagnation under long-term cultivation and its relationship with soil organic matter fractions are rarely considered. To understand this phenomenon, soil organic matter fractions and soil aggregate size distribution were studied in a long-term experiment at Akola, in a Vertisol in a semiarid tropical environment. For 14 years, the following fertiliser treatments were compared with undisturbed fallow plots: unfertilised (control), 100% recommended rates of N, NP, NPK (N : P : K ratios of 100 : 21.8 : 18.2 and 120 : 26.2 : 50 kg/ha for sorghum and wheat, respectively) and 100% NPK plus farmyard manure (FYM) and continuous cropping with a sorghum (Sorghum bicolor L. Moench) and wheat (Triticum aestivum L.) system during 1988–2001. The significant negative yield trend was observed in unbalanced use of inorganic N application for both crops. However, yields were maintained when NPK and NPK + FYM were applied. Results showed that soil organic C and total N in the unfertilised plot decreased by 21.7 and 18.2%, compared to the initial value, at a depth of 0–15 cm. Depletion of large macroaggregates (>2 mm) accounted for 22–81% of the total mass of aggregates in N, NP and unfertilised control plots compared to fallow plots. Irrespective of treatments, small macroaggregates (0.25–2 mm) dominated aggregate size distribution (56–71%), followed by microaggregates (0.053–0.25 mm, 18–37%). Active fractions, such as microbial biomass C, microbial biomass N, hot water soluble C and N, and acid hydrolysable carbohydrates were greater in NPK and NPK + FYM treatments than in the control. Carbon and N mineralisation were greater in small macroaggregates than microaggregates. Particulate organic matter C (POMC) and N (POMN) were significantly correlated (P < 0.01) with water-stable aggregate C and N (0.25–2 mm size classes), respectively. It was further observed that POMC and POMN were significantly greater in NPK and NPK + FYM plots than N and NP treated plots. Microbial biomass C was positively correlated with acid-hydrolysable carbohydrates (r = 0.79, P < 0.05). Continuous cropping and fertiliser use also influenced humic acid C and fulvic acid C fractions of the soil organic matter. Acid-hydrolysable N proportion in humic acid was greater than fulvic acid and it was greatest in NPK + FYM treatments. Continuous application of 100% NPK + FYM could restore soil organic carbon (SOC) to a new equilibrium level much earlier (t = 1/k, 2.4 years) than N (t = 1/k, 25.7 years), NP (t = 1/k, 8.1 years) and NPK (t = 1/k, 5.02 years). In conclusion, integrated use of NPK with FYM would be vital to obtain sustainable yields without deteriorating soil quality.

Effect of 12 years' rice/wheat cropping sequence and fertilizer use on soil properties and crop yields in a sodic soil

Abstract In a field experiment initiated in 1974 on a sodic soil (pH 9.2 exchangeable sodium percentage 32), continuous cropping with rice (Oryza sativa L.) and wheat (Triticum aestivum Linn. emend. Fiori and Paol) grown in rotation for 12 years (1974/75 to 1985/86) reduced the available N, P, and K from the initial levels of 225, 33.6 and 358 kg ha−1 to 120, 17.9 and 318 kg ha−1 in unfertilized plots (control). Continuous use of fertilizer N alone (120 kg ha−1) or in combination with P and K significantly enhanced the yield of crops and available N. Phosphorus applied at a rate of 22 kg P ha−1 to either or both rice and wheat in rotation significantly improved the yield of rice from 1979 onwards but that of wheat only during 1985/86, and led to a considerable build-up in available soil P. Where N alone was applied, available P and K declined from the initial level of 33.6 and 358 kg ha−1 to 8.7 and 280 kg ha−1. Potassium applied at a rate of 42 kg K ha−1 to either or both crops had no effect on yields. Application of N, P and K enhanced the concentration and uptake of these elements in the crops. Continuous cropping for 12 years reduced soil pH from 9.2 to 8.5 and exchangeable sodium percentage ( esp ) from 32 to 8.0, there being no differential effect due to treatments.

Build up and depletion of soil phosphorus and potassium and their uptake by rice and wheat in a long-term field experiment

SummaryIn a field experiment initiated at the Central Soil Salinity Research Institute, Karnal in 1974 involving rice wheat cropping sequence and NPK fertilizer use on sodic soil (pH 9.2, ESP 32.0), an attempt was made to evaluate the available P and K status of the soil and their uptake by the crops during 1982–83 and 83–84.Application of P to either or both the crops significantly enhanced the yields of rice and improved available P status of the soil. Wheat yields remained unaffected. Fertilizer N reduced P content in rice but increased P uptake in crops and considerably brought down available P to a level (4.5 ppm) where rice plants showed reduced tillering and phosphorus deficiency. Application of K did not affect the yield of either crop but enhanced its available status in soil and uptake by the crops. Contribution of the non-exchangeable K towards total potassium removal was about 93% in the absence of applied K which decreased to 87% with the use of K. Application of K to both crops resulted in lesser uptake from non-exchangeable form as compared to its application to either crop. Laboratory studies carried out on soils of the experimental plots showed that cumulative K release measured after five successive extractions was higher in K-treated soils as compared to untreated ones. The major difference was only in the first extraction representing the exchangeable K after which release became independent of the available K of the soil.

Availability of iron, manganese, zinc and phosphorus in submerged sodic soil as affected by amendments during the growth period of rice crop

SummaryEffect of amendments, gypsum (12.5 tonnes/ha), farmyard manure (30 tonnes/ha), rice husk (30 tonnes/ha) and also no amendment (control) on the availability of native Fe, Mn and P and applied Zn in a highly sodic soil during the growth period of rice crop under submerged conditions was studied in a field experiment. Soil samples were collected at 0, 30, 60 and 90 days of crop growth. Results showed that extractable Fe (1N NH4OAC pH 3) and Mn (1N NH4OAC pH 7) increased with submergence upto 60 days of crop growth but thereafter remained either constant or declined slightly. Application of farmyard manure and rice husk resulted in marked improvement of these elements over gypsum and control. Increases in extractable Mn (water soluble plus exchangeable) as a result of submergence and crop growth under different amendments were accompanied by corresponding decreases in easily reducible Mn content of the soil. Application of 40 kg zinc sulphate per hectare to rice crop could substantially raise the available Zn status (DTPA extractable) of the soil in gypsum and farmyard manure treated plots while the increase was only marginal in rice husk and control plots indicating greater fixation of applied Zn. Available P (0.5M NaHCO3 pH 8.5) behaved quite differently and decreased in the following order with crop growth: gypsum>rice husk>farmyard manure>control.

Effect of exchangeable sodium percentage and presubmergence on yield and nutrition of rice under field conditions

SummaryThe effects of exchangeable sodium percentage (ESP) levels of 82, 72, 65 and 35 and 0, 15 and 30 days of presubmergence (submergence prior to the transplanting of rice) on yield and chemical composition of rice and availability of Fe, Mn, Zn and P in soil were studied factorially in a field experiment. Presubmergence increased rice yields at all ESP levels, the effect being more pronounced at high ESPs. Increasing ESP decreased yields and the contents of Ca, Mg, K, Fe, Mn, Zn and Cu but increased that of P and Na in the crop. Presubmergence enhanced absorption of all the above elements by the crop except P, K, Mg, Zn and Cu in the grain and decreased Na in grain and straw. Growing of rice under submerged conditions also facilitated the improvement of these soils. Effects of submergence and ESP on the availability of Fe, Mn, Zn and P in soil and their role in the nutrition of rice are discussed. The results suggest that 15 to 30 days presubmergence improved rice yields on a calcareous sodic soil of the Indo-Gangetic alluvial plain.

Influence of organic matter and flooding on the chemical and electrochemical properties of sodic soil and rice growth

The influence of organic matter, added in the form ofCasuarina equisetifolia andAcacia nilotica leaves, on the chemical and electrochemical kinetics of a flooded sodic soil and rice growth, was studied in a pot experiment. With the addition of organic matter, not only the peaks of CO2 production and maximum concentrations of extractable Fe and Mn and other cations occurred earlier, but their concentrations were also significantly higher as compared to the control (no organic matter). The high concentrations of CO2 and reduced redox potential (Eh) appeared to influence the soil pH, exchangeable sodium percentage (ESP) and the accumulation of cations and to be chiefly responsible for better rice growth. Acacia proved more effective than Casuarina in improving rice yield and the sodic soil.

DIAGNOSIS AND RECOMMENDATION INTEGRATED SYSTEM APPROACH FOR NITROGEN, PHOSPHORUS, POTASSIUM, AND ZINC FOLIAR DIAGNOSTIC NORMS FOR AONLA IN CENTRAL INDO-GANGETIC PLAINS

A survey was conducted for the nutritional status of aonla orchards in the state of Uttar Pradesh lying in Central Indo-Gangetic plains. Preliminary diagnosis and recommendation integrated system (DRIS) norms were established for different nutrient ratios and used to compute the DRIS indices, which assessed the nutrient balance and order of limitations to yield. Maximum fruit yield of 40.2 kg plant−1 was recorded for the plants at the age group of 10–15 years and lowest yield was recorded 28.3 kg plant−1 in the age of above 20 years. Nutrient sufficiency ranges for aonla derived from DRIS norms were 1.30– 1.64, 0.054–0.092, 0.40–0.64%, and 32.4–45.9 ppm for nitrogen (N), phosphorus (P), potassium (K), and zinc (Zn), respectively. On the basis of these sufficiency ranges 33, 51, 47, and 46% of samples were found sufficient whereas 34, 22, 18 and 27% of samples were low and 26, 8, 1 and 17% deficient in N, P, K, and Zn, respectively. When compared age wise, a relative deficiency for N, P, and K corresponding to relative sufficiency for Zn was detected by DRIS technique for the plants above the age group of 15 onwards. For the younger orchards (5yrs old) a relative deficiency of N, Zn, and K corresponding to the relative sufficiency of P was detected. Nitrogen was found most limiting elements in all age group of plant. When the DRIS indices were compared on basis of soil pH, Zn and K was found to be relatively lesser in order of requirement than N and P.