D. S. Rana

Influence of growing various crops in five different fixed rotations on the changes in nitrate and total nitrogen content of soils

The results on the influence of various crops in five different fixed rotations on the ohanges in nitrate and total N content of soils are reported. Groundnut contributed largely to the accumulation of nitrate nitrogen in the soil profile (to a depth of 120 cm). Bajra fodder exhausted the soil nitrogen reserve to a great extent. Wheat and maize, in a rotation, reduced nitrate leaching to deeper soil layers. Summer moong also left a large amount of unabsorbed nitrate in the profile. Total nitrogen content of the soil decreased after the harvest of cereals. Maximum depletion occurred after the harvest of bajra crop. Potato (a crop which received a heavy dressing of N fertilizer) and legumes contributed to the soil N reserve. A balance sheet of N indicated net gains of total soil N in four of the five cropping sequences. A net loss of 75 kg N/ha was observed in bajra fodder-potato-wheat rotation.

Some measures of reducing leaching loss of nitrates beyond potential rooting zone: IV. Intercropping

SummarySoil nitrate profiles under seven treatments of an experiment on intercropping in row crops were studied at sowing and the after harvesting of different crops. The estimates of NO3−−N in these profiles indicate that intercropping in the row crops grown during the rainy season considerably reduced leaching loss of nitrates. Where the main crop receives the recommended fertilizer amount and the intercrop a small additional application, intercropping greatly reduced the amount of unutilized nitrates and hence their leaching beyong root zone.

The quantity-intensity relations of potassium in soils from plots having nine fixed crop rotations for six years

SummarySoil samples collected 6 years after raising of various cereals, pulses, oil seed and tuber crops in nine fixed rotations were used to study the quantity-intensity relations of potassium. Potassium activity ratio, where the soil neither gains nor looses K, was correlated in a highly significant manner (P = 0.01) with the total amount of K fertilizer applied during 6 years. The K buffering capacity, the slope of the Q/I curve, when the soil neither gains nor looses K, was positively correlated (P = 0.05) with K saturation of the total and inorganic cation exchange capacities to a similar extent. Superimposing Q/I curves showed no appreciable difference between samples from different treatments. Desorption of potassium with increasing soil∶solution (0.01M CaCl2) ratio followed a Langmuir type of equation and supported the conclusions drawn from quantity-intensity curves.