No abstract

Field experiments were conducted at Agricultural Experimental Farm, Giridih, Bihar during the winter seasons of 1992–93 and 1993–94 to compare 1 : 1 and 2 : 1 row‐replacement series intercropping of mustard (Brassica campestris Var. Toria) with pea (Pisum sativum), with lentil (Lens culinaris) and with gram (Cicer areitinum L.). Intercropping systems were assessed on the basis of new indices termed ‘actual yield loss’ (AYL) and ‘intercropping advantage’ (IA), as well as several existing intercropping indices such as LER, RCC and aggressivity. Intercropping reduced the yield of component crops, compared with respective pure stands. Mustard + pea in 1 : 1 row‐replacement series gave the highest mustard yield equivalent value (1.00 t/ha). When the actual sown proportion was considered, mustard + lentil (1 : 1) resulted in maximum AYL (+0.438) and IA (+2.889) values. We conclude that AYL and IA are more appropriate, particularly when per plant yield is considered.

The effect of organic sources of nutrients and inorganic fertilizers, was studied on grain yield of lowland rice and some aspect of soil quality parameters in a field experiment at Agricultural Experimental Farm of Indian Statistical Institute, Giridih, situated at eastern plateau region of India, during consecutive years 1997-2002. Chemical fertilizers and various organic matters were applied to two rice cultivars, Sabita and Subarna. The highest mean grain yield was 3.53 t ha )1 and maximum agronomic efficiency was 60.3 % with the application of inorganic fertilizer followed by cow dung, where 3.47 t ha )1 grain yield was recorded with an agronomic efficiency of 57.5 %. Grain yield of rice recorded under organic sources of nutrients was not significantly different from that of inorganic fertilization though there was improvement in soil quality parameters under organic sources. Soil organic carbon (0.72 %), microbial biomass-C (279.23 lg g )1 dry soil), urease activity with buffer (33.54 lg urea hydrolyzed g )1 oven-dry soil) and nonbuffer (21.97 lg urea hydrolyzed g )1 of oven-dry soil) methods and acid phosphatase activity (2.24 lg paranitrophenol released g )1 of oven-dry soil) analysed following the harvest of the crop were highest under cow dung manure treatment; the most efficient organic source under the experiment. Mean grain yield of rice was significantly higher in Sabita cultivar over Subarna. The regression analyses among the variables have shown that there was linear relationship among soil parameters and grain yield of rice.

Phosphate rocks (PRs) are suitable for direct application as a possible alternative to more expensive soluble phosphate fertilizers in agricultural fields. But the ability of the PRs to release phosphates in the plant available forms depends on the particle size and chemical and mineralogical characteristics of the PRs as well as the properties of the soil in which they are applied. So an experiment was conducted with four sources of phosphatic fertilizers namely Triple super phosphate (TSP-21.75%P)), Partially acidulated phosphate rock (PAPR-12.97%P)), Morocco rock phosphate (MORP-14.87%P)) and Mussoorie rock phosphate (MRP-8.12%P) whose solubility were tested in six different extractants namely 2% Citric acid, 0.002N Hydrochloric acid, N-Ammonium citrate, Bray-2P extractant, Olsens's extractant and Morgan's reagent under seven periods of incubation (1, 2, 3, 7, 10, 15 and 30 days), with and without soil. The results revealed that release of P were increased on addition of soil irrespective of fertilizers or extractants used. TSP released maximum P (3.05%-3.27% with soil, 2.11%-2.22% without soil) by the 7th day of incubation. The partially acidulated source was found to release P, higher than rock phosphates but lower than TSP, for the initial periods of incubation (1-3 days) (1.31%-1.34% with soil, 0.46% without soil) with an increase in the later periods (7th day onward) (1.27%-1.92% with soil, 0.55%-0.66% without soil). The PRs released maximum P after the 7th day of incubation. Among the different solvents, maximum release of phosphorus was observed by 2% citric acid followed by Bray 2P and Olsen's extractants.

The Relative Agronomic Effectiveness (RAE) of rock phosphates as compared to water soluble Triple Super Phosphate was measured on direct, residual, and cumulative application of the P fertilizers in a field experiment with rice on an Oxic‐Rhodustalf in the eastern plateau region of India. The fertilizers were Morocco Rock Phosphate (MORP), Mussoorie Rock Phosphate (MRP), Partially Acidulated Rock Phosphate (PARP), and Triple Super Phosphate (TSP). The RAE of the rock phosphates were lower for direct application (54–80 %) and cumulative application (70–93 %) of P but roughly equal or larger for the residual effect (92–142 %) as compared to TSP. The P adsorption characteristic of the experimental soil conformed to the linear relationship of both Freundlich and Langmuir isotherm equation. The adsorption data when plotted according to Langmuir equation deviated from a single linear relationship at higher concentration (10 μg ml–1), thereby giving two adsorption maximum values ( 68.49 μg g–1 and 256.41 μg g–1) and binding energies ( 2.86 ml μg–1 and 0.089 ml μg–1) for the soil. Two populations of P adsorption site with widely different affinity for P probably existed in the soil.