The Role of Soil Organic Matter and Manures in Sustainable Nutrient Cycling - Sustainable Management of Soil Organic Matter - page 275

than in the household, while relatively more manure is applied in the
household than in the experiments, which suggests that a household is
relatively independent of external sources of N. Overall, the total N inputs
in a hypothetical household are greater than those in the experiment.
Table 4.7.2 shows the average crop yields in two seasons for all seven
treatments from the two experiments at ARS-Pakhribas compared with
the yields used to generate the data in Fig. 4.7.1. In most cases, grain and
straw yields were greater in the experimental data than in the data for
the household. Similarly, the tissue N concentrations were generally
greater for the experimental data than the 10 or 5 mg g −1 N used for grain
and straw, respectively, in the calculations for the hypothetical household.
Consequently, fluxes of N in grain (i.e. crossing the household boundary)
or in straw (i.e. cycling internally as animal fodder) are greater in the
experimental conditions than predicted from the literature.

Fluxes in leachate

Ceramic cup solution samplers were installed at three experimental sites
(Pakhribas, Dordor Gaun and Dordor Tar) on bari land in the mid-hills of
Nepal in 1998. They were installed to a depth of 75 or 90 cm in three of the
seven experimental treatments described above, namely zero input, manure
only and fertilizer only, both applied at the higher rate of N.
Table 4.7.3 shows the average concentration of nitrate in the soil solu-
tion collected between the end of June and mid-October in the ceramic
cups at 50 kPa suction applied for 24 h. There seems to be little difference

Table 4.7.2. Average grain and straw yields (kg ha − 1 ) and tissue N concentrations (mg g − 1 ) from
experiments including four crops at ARS-Pakhribas in 1997 and 1998, and grain and straw yields
used in the hypothetical household.

Experimental yield Experimental tissue concentration

Hypothetical
household

1997 1998 1997 1998

Maize Grain 2000 3590 1980 14.6 14.2

Straw 3000 3513 ND 7 .6 8.1

Millet Grain 1160 1937 2033 10.8 7.9

Straw 1740 3391 2347 5.7 8.2

Rice Grain 2000 1835 2593 12.2 12.8

Straw 3000 4811 4333 8.7 6.8

Wheat Grain 2500 2437 3148 25.1 ND

Straw 3750 3717 4760 3.5 ND

ND denotes not determined.