Wheat and mustard 1. Wheat

There was wide variation in germination percentage and dry-matter yields at Z30 amongst replications. Nitrogen and P contents were higher in the N- and P-fertilized treatments during the first two years. However, during the third and fourth years these differences were very much less as the wheat was sown without tillage operation and cowpea-stover residues were retained to conserve moisture. Grain yield was significantly influenced by N and P applications (Table VIII). Grain-N

content also showed an increasing trend with N and P applications, but straw N content increased only at the higher level of N. During the second year, the grain yield was much lower than in the first year, mainly because of less winter rainfall: only 42.5 mm compared to 130 mm in 1998–1999.

In the third and fourth years, winter rains were much less than the seasonal average of 75 mm as in the second year (1999–2000). However, even then, both crops showed good growth and production especially with application of both N and P (Tables VIII and XIV). The highest wheat grain yield of 1.89 Mg ha^–1 was obtained with 80 kg N ha^–1 and 40 kg P2O5 ha^–1. Moisture retention in the soil profile also was much higher compared to the previous two years, as a result of minimum tillage and mulching. Neutron-probe data indicated very little loss of water, consistent with visual observations from mid-December to end of January: the stover mulch was wet, particularly as a result of conservation of overnight dew.

Tables IX to XII show trends in increasing total-N, total-P, uptake of fertilizer N and P as well as use efficiency of fertilizer N and fertilizer P similar to those observed with wheat grain yields in response to applications of increasing levels of N and P.

Total N and fertilizer N uptake by wheat grain (from 9.10 to 24.7 kg ha^–1) and in wheat straw (from 4.10 to 10.6 kg ha^–1) were significantly increased by N and P application. The fertilizer-N recovery ranged from 14 to 26% (Table X), and was higher with the lower level of N application. The application of P significantly increased the fertilizer-N recovery. The fertilizer-N-use efficiency in the second year was nearly half that of the first year mainly due to less favourable soil-moisture conditions, resulting in significant declines in grain and total dry matter yields. However, in the third and fourth years due to soil-moisture conservation from mulching and minimum tillage, there were significant increases in wheat grain yields and, consequently, in N and P uptake; use efficiencies of fertilizer N and P were also increased.

Residual fertilizer N in the soil after wheat harvest was between 65% and 75% and it is presumed that the remaining 9.4 to 11% was lost by ammonia volatilization; no ¹⁵N could be traced below a depth of 15 cm, except in the first year when some fertilizer N was leached to 15 to 30 cm as a result of higher rainfall.

Table IX. Effects of applied nitrogen and phosphorus on total nitrogen uptake by wheat N treatment

N₀ N₄₀ N₈₀ Mean Season P treat.

(kg N ha^–1)

Factor SEM (±) C.D.

at 5%

1998–1999 P₀ 13.7 28.4 39.8 27.3 N 0.77 2.24 P₂₀ 18.9 33.7 49.0 33.9 P 0.77 2.24 P₄₀ 21.5 38.1 53.4 37.7 N × P 1.34 NS Mean 18.0 33.4 47.4

1999–2000 P0 13.2 19.7 29.6 20.8 N 0.34 0.99 P20 15.1 20.9 33.0 23.0 P 0.34 0.99 P40 16.0 27.2 35.2 26.1 N × P 0.59 1.71 Mean 14.8 22.6 32.6

2000–2001 P₀ 12.6 26.2 37.5 25.4 N 0.42 1.20 P₂₀ 17.2 30.1 43.8 30.4 P 0.42 1.20 P₄₀ 21.0 36.6 50.3 36.0 N × P 0.72 NS Mean 16.9 31.0 43.9

2001–2002 P0 12.0 23.5 30.8 22.1 N 0.30 0.87 P₂₀ 14.9 25.5 36.6 25.7 P 0.30 0.87 P₄₀ 17.1 29.7 39.4 28.7 N × P 0.52 1.50 Mean 14.7 26.3 35.6

Table X. Effects of applied nitrogen and phosphorus on fertilizer-nitrogen recovery by wheat N treatment

N0 N40 N80

Season P treat. Mean

(%)

Factor SEM (±) C.D. at 5%

1998–1999 P₀ – 31 24 28 N 0.72 2.13 P₂₀ – 38 30 34 P 0.88 2.61

P₄₀ – 44 34 39 N × P 1.24 NS

Mean – 38 29

1999–2000 P₀ – 18 14 16 N 0.29 0.85 P20 – 19 16 18 P 0.35 1.04

P₄₀ – 26 18 22 N × P 0.50 1.48

Mean – 21 16

2000–2001 P₀ – 29 22 26 N 0.43 1.27 P₂₀ – 33 26 30 P 0.52 1.56

P₄₀ – 42 31 36 N × P 0.74 2.20

Mean – 35 26

2001–2002 P₀ – 24 17 20 N 0.36 1.08 P₂₀ – 26 20 23 P 0.44 1.32

P₄₀ – 32 23 27 N × P 0.63 NS

Mean – 27 20

Table XI. Effects of applied nitrogen and phosphorus on total phosphorus uptake by wheat N treatment

N₀ N₄₀ N₈₀ Mean Season P treat

(kg P₂O₅ ha^–1)

Factor SEM (±) C.D.

at 5%

1998–1999 P₀ 4.71 9.16 12.3 8.73 N 0.26 0.74 P₂₀ 7.79 12.6 19.6 13.3 P 0.26 0.74 P₄₀ 9.37 15.2 22.1 15.6 N × P 0.44 1.29

Mean 7.29 12.3 18.0

1999–2000 P₀ 4.91 7.18 9.89 7.33 N 0.15 0.44 P₂₀ 6.62 9.17 14.2 9.98 P 0.15 0.44 P₄₀ 7.40 12.1 15.5 11.7 N × P 0.26 0.76

Mean 6.31 9.48 13.2

2000–2001 P0 5.63 11.4 15.3 10.8 N 0.27 0.77 P20 9.03 15.5 23.2 15.9 P 0.27 0.77 P40 11.5 19.1 27.0 19.2 N × P 0.46 1.33

Mean 8.73 15.3 21.9

2001–2001 P₀ 5.21 10.1 12.9 9.41 N 0.15 0.43 P₂₀ 7.41 13.2 18.7 13.1 P 0.15 0.43 P₄₀ 9.53 14.6 21.6 15.2 N × P 0.26 0.74

Mean 7.38 12.7 17.7

The P contents of wheat grain and straw were influenced by N and P application and increased with increasing levels of each (Tables X and XI). The interaction of N and P application on P content of wheat grain was positive. Total P uptake by wheat ranged from 4.70 to 22.1 kg P₂O₅ ha^–1 and from 0.37 to 1.23 kg P ha^–1 came from fertilizer. Fertilizer-P recovery by wheat ranged from 3.0 to 22% and increased significantly with increasing levels of applied N. Fertilizer P recovery was between 7.2 and 14% at 20 kg P O ha^–1 and between 5.1 to 12% at 40 kg P O ha^–1. Fertilizer-P recovery by wheat was

significantly influenced by an N × P interaction. However, during the second year, like all other parameters, fertilizer P recovery was low. In the third and fourth years, there were significant increases in the fertilizer-P-use efficiency, with rainfall more or less similar to that of the second year, mainly because of the water-conservation effects of the cowpea stover mulch and minimum tillage.

Consumptive water-use efficiencies in the third and fourth years were some 50 to 100% greater than that observed in the second year (Table XIII).

Table XII. Fertilizer-phosphorus recovery by wheat N treatment

N₀ N₄₀ N₈₀ Mean Season P treatment

(%)

Factor SEM (±) C.D.

at 5%

1989–1999 P₂₀ 5.5 9.96 16 10.6 N 0.25 0.73

P₄₀ 4.2 7.00 10 7.14 P 0.20 0.60

Mean 4.8 8.48 13 N × P 0.35 1.03

1999–2000 P₂₀ 4.2 6.42 11 7.17 N 0.13 0.40

P₄₀ 3.0 5.18 7.0 5.08 P 0.11 0.32

Mean 3.6 5.80 8.9 N × P 0.19 0.56 2000–2001 P₂₀ 6.2 12 22 13.5 N 0.45 1.33

P40 5.4 11 18 11.3 P 0.37 1.09

Mean 5.8 12 20 N × P 0.64 1.89

2001–2002 P₂₀ 5.7 12 18 11.9 N 0.18 0.53

P₄₀ 4.8 8.9 15 9.48 P 0.14 0.43

Mean 5.2 11 16 N × P 0.25 0.74

Table XIII. Effects of applied nitrogen and phosphorus on water-use efficiency of wheat N treatment

N₀ N₃₀ N₆₀ Mean Season P treat

(kg/ha-mm)

Factor SEM (±) C.D.

at 5%

1998–1999 P0 2.39 4.70 6.33 4.47 N 0.06 0.18

P20 3.21 5.23 7.08 5.17 P 0.06 0.18

P40 3.59 6.00 7.79 5.79 N × P 0.10 NS

Mean 3.06 5.31 7.06

1999–2000 P₀ 2.57 3.39 5.16 3.70 N 0.04 0.12

P₂₀ 2.79 3.53 5.53 3.95 P 0.04 0.12

P₄₀ 2.82 4.94 5.82 4.53 N × P 0.07 0.21 Mean 2.73 3.95 5.50

2000–2001 P0 2.64 5.29 7.22 5.05 N 0.08 0.24

P₂₀ 3.44 6.20 8.50 6.04 P 0.08 0.24

P₄₀ 4.40 7.17 9.53 7.03 N × P 0.15 NS

Mean 3.50 6.22 8.41

2001–2002 P₀ 2.50 4.93 6.55 4.86 N 0.07 0.21

P₂₀ 3.24 5.73 7.82 5.60 P 0.07 0.21

P₄₀ 4.09 6.60 8.69 6.46 N × P 0.13 NS

Mean 3.28 5.75 7.68

Table XIV. Effects of applied nitrogen and phosphorus on seed yield of mustard N treatment

N0 N30 N60

Season P treat. Mean

(q ha^–1)

Factor SEM (±) C.D.

at 5%

1998–1999 P₀ 4.15 7.63 10.8 7.53 N 0.13 0.36 P₁₅ 4.57 12.0 14.3 10.3 P 0.13 0.36 P₃₀ 4.56 13.2 14.00 10.6 N × P 0.22 0.63

Mean 4.43 11.0 13.0

1999–2000 P₀ 3.86 6.36 9.07 6.43 N 0.11 0.30 P15 4.08 9.88 11.3 8.41 P 0.11 0.30 P₃₀ 4.20 11.0 11.1 8.76 N × P 0.18 0.53

Mean 4.05 9.06 10.5

2000–2001 P₀ 4.53 8.25 11.9 8.23 N 0.13 0.39 P₁₅ 4.90 12.4 15.1 10.8 P 0.13 0.39 P₃₀ 5.12 13.8 15.9 11.6 N × P 0.23 0.67

Mean 4.85 11.5 14.3

2001–2002 P₀ 4.64 7.69 10.9 7.75 N 0.11 0.31 P₁₅ 5.04 11.7 13.7 10.2 P 0.11 0.31 P₃₀ 5.36 13.0 14.8 11.0 N × P 0.19 0.54

Mean 5.01 10.8 13.1

4.2.2. Mustard

Mustard seed yields ranged from 3.90 to 15.9 q ha^–1 and were significantly increased by application of both N and P (Table XIV). The mean effect of application of only 30 kg N ha^–1 was an increase of more than 100% seed yield and with application at 60 kg N ha^–1 it increased by nearly 200%. Seed yield also increased with P application and a positive N × P interaction affected seed yield. Stover yield was significantly influenced by N application only. Similar to wheat, mustard showed much better growth during the third and fourth years even though winter rains were less compared to those of the second year and were only about 50% of the long-term average. Seed yields were also higher than in the first year when winter rains were much higher than the average. Nitrogen and P applications significantly increased N contents in seed, stover and pod-husk (data not presented).

Phosphorus contents in all parts of mustard were significantly increased by N or P application;

however, only stover P content was significantly increased with both N and P applied.

There were significant increases in total N and P uptake with both N and P applications and their interaction was also statistically significant (Tables XV and XVII). The %Ndff values in various components of the mustard crop ranged from 33 to 42, and greater with the higher level of N (60 kg N ha^–1) (data not presented). Fertilizer-N uptake by mustard seeds ranged from 7.80 to 14.9 kg ha^–1 at 30 kg N ha^–1 and from 14.7 to 18.7 kg ha^–1 at 60 kg N ha^–1; it was increased significantly by both N and P application (data not presented). Fertilizer-N recovery by mustard was 34 to 64% in the first year, 31 to 61% per cent in the second year, and during the third and fourth years very significant increases in the fertilizer-N-use efficiency were obtained, ranging between 37 to 76% a result of water conservation (Table XVI). Application of P significantly increased fertilizer-N recovery by the crop.

This was primarily as a result of better exploitation of soil water even from deeper soil layers and consequently much higher uptake of nutrients—a similar trend prevailed in uptake of P.

The %Pdff values ranged from 18 to 32 and were higher in seed than in stover or pod-husk portions.

The total fertilizer P recovered in the mustard was 6.00 to 31.9 kg ha^–1 at 15 kg P₂O₅ ha^–1 and 6.57 to 29.8 kg ha^–1 at 30 kg P2O5 ha^–1 (Table XVII). Nitrogen application showed a highly significant effect on percent recovery of fertilizer P, from as low as 5.2 in the second year with application of 30 kg P O ha^–1 at zero N to 32% at 15 kg P O ha^–1 with 60 kg N ha^–1 application (Table XVIII).

Table XV. Effects of applied nitrogen and phosphorus on nitrogen uptake by mustard N treatment

N0 N30 N60

Season P treat Mean

(kg ha^–1)

Factor SEM (±) C.D.

at 5%

1998–1999 P₀ 19.2 34.8 52.2 35.4 N 0.96 2.79 P₁₅ 22.2 52.1 61.8 45.4 P 0.96 2.79 P₃₀ 21.3 56.3 60.4 46.0 N × P 1.66 4.83

Mean 20.9 47.7 58.1

1999–2000 P₀ 17.6 31.1 45.4 31.4 N 0.53 1.53 P15 19.7 46.1 54.6 40.1 P 0.53 1.53 P₃₀ 20.4 50.9 55.5 42.3 N × P 0.92 2.66

Mean 19.3 42.7 51.8

2000–2001 P₀ 22.2 39.0 59.2 40.1 N 0.60 1.74 P₁₅ 24.1 57.1 72.6 51.3 P 0.60 1.74 P₃₀ 25.4 63.1 75.3 54.7 N × P 1.04 3.01

Mean 23.9 53.1 69.0

2001–2002 P₀ 21.4 35.2 53.5 36.7 N 0.55 1.59 P₁₅ 23.7 53.0 64.6 47.1 P 0.55 1.59 P₃₀ 26.3 59.1 70.7 52.1 N × P 0.95 2.75

Mean 23.8 49.1 63.0

Table XVI. Effects of applied nitrogen and phosphorus on fertilizer-nitrogen recovery by mustard N treatment

N₀ N₃₀ N₆₀ Mean Season P treat.

(%)

Factor SEM (±) C.D.

at 5%

1998–1999 P₀ – 34 34 34 N 1.20 3.58

P₁₅ – 55 42 48 P 1.47 4.38

P30 – 64 42 53 N × P 2.08 6.19

Mean – 51 39

1999–2000 P₀ – 34 31 33 N 0.64 1.91

P₁₅ – 54 38 46 P 0.79 2.34

P₃₀ – 61 39 50 N × P 1.11 3.31

Mean – 49 36

2000–2001 P0 – 52 43 48 N 0.77 2.29

P15 – 70 54 62 P 0.95 2.81

P30 – 76 55 66 N × P 1.34 3.97

Mean – 66 50

2001–2002 P₀ – 44 37 40 N 0.52 1.55

P₁₅ – 62 45 54 P 0.64 1.90

P₃₀ – 72 51 62 N × P 0.91 2.69

Mean – 59 44

There was no influence of N and P application or the season on seed-oil content (Table XIX).

However, total oil yield was significantly increased by graded increased N and P application and their interaction was also significant (Table XX). The application of 30 kg N ha^–1 and 15 kg P₂O₅ ha^–1 increased the oil yield by nearly 140%. Thus showing that even under adverse rainfed conditions, fertilizer application to mustard can have higher economic returns.

The balance-sheet of fertilizer N showed that less than 10% of the applied N could not be accounted for; 90% was accounted for either as taken up by the crop or residual in the soil (data not presented).

Table XVII. Effects of applied nitrogen and phosphorus on fertilizer-phosphorus uptake by mustard N treatment

N₀ N₃₀ N₆₀ Mean Season P treat.

(kg ha^–1)

Factor SEM (±) C.D.

at 5%

1998–1999 P₀ 5.08 8.08 13.0 8.73 N 0.31 0.89 P15 6.59 14.5 18.2 13.1 P 0.31 0.89 P₃₀ 6.86 16.5 18.9 14.1 N × P 0.53 1.55

Mean 6.18 13.1 16.7

1999–2000 P₀ 4.52 7.70 10.4 7.5 N 0.18 0.51 P₁₅ 6.00 12.4 15.3 11.2 P 0.18 0.51 P₃₀ 6.57 14.4 16.1 12.4 N × P 0.31 0.89

Mean 5.70 11.5 13.9

2000–2001 P₀ 11.1 15.4 22.1 16.2 N 0.65 1.90 P₁₅ 14.8 22.3 31.9 23.0 P 0.65 1.90 P₃₀ 16.3 26.3 29.8 24.1 N × P 1.13 3.29

Mean 14.1 21.3 27.9

2001–2002 P0 8.68 13.0 19.2 13.6 N 0.49 1.41 P15 13.2 19.9 26.5 19.9 P 0.49 1.41 P30 16.1 25.5 28.3 23.3 N × P 0.84 2.45

Mean 12.7 21.3 24.7

Table XVIII. Effects of applied nitrogen and phosphorus on fertilizer-phosphorus recovery by mustard N treatment

N0 N30 N60

Season P treat. Mean

(%)

Factor SEM (±) C.D.

at 5%

1998–1999 P₁₅ 7.9 22 30 20 N 0.41 1.23 P₃₀ 5.8 15 19 13 P 0.34 1.01 Mean 6.8 19 25 N × P 0.59 1.74 1999–2000 P15 6.8 18 24 16 N 0.38 1.14 P30 5.2 13 15 11 P 0.31 0.93 Mean 6.0 15 19 N × P 0.54 1.61 2000–2001 P₁₅ 9.7 24 32 22 N 0.52 1.54 P₃₀ 7.4 19 23 16 P 0.42 1.26 Mean 8.6 21 27 N × P 0.74 2.18 2001–2002 P¹⁵ 7.6 19 25 17 N 0.19 0.56 P₃₀ 6.4 15 18 13 P 0.16 0.46 Mean 7.1 17 225 N × P 0.27 0.80

Table XIX. Effects of applied nitrogen and phosphorus on oil content of mustard seeds N treatment

N0 N30 N60

Season P treat. Mean

(%)

Factor SEM (±) C.D.

at 5%

1998–1999 P₀ 41 40 41 41 N 0.20 NS

P₁₅ 40 40 41 40 P 0.20 NS

P₃₀ 40 41 40 40 N × P 0.35 NS

Mean 40 40 40

1999–2000 P₀ 41 40 41 41 N 0.20 NS

P15 40 40 41 40 P 0.20 NS

P₃₀ 40 41 40 40 N × P 0.35 NS

Mean 40 40 40

2000–2001 P₀ 41 41 41 41 N 0.16 NS

P₁₅ 40 41 41 41 P 0.16 NS

P₃₀ 41 41 41 41 N × P 0.27 NS

Mean 41 41 41

2001–2002 P₀ 41 41 41 41 N 0.08 NS

P₁₅ 41 41 41 41 P 0.08 NS

P₃₀ 41 41 41 41 N × P 0.15 NS

Mean 41 41 41

Table XX. Effects of applied nitrogen and phosphorus on yield of mustard oil N treatment

N₀ N₃₀ N₆₀ Mean Season P treat.

(kg ha^–1)

Factor SEM (±) C.D. at 5%

1998–1999 P₀ 169 308 437 305 N 5.1 14.8 P15 181 486 580 416 P 5.1 14.8 P₃₀ 183 534 563 427 N × P 8.8 25.6 Mean 178 443 527

1999–2000 P₀ 157 256 367 260 N 4.4 12.9 P₁₅ 162 399 457 339 P 4.4 12.9 P₃₀ 169 444 448 353 N × P 7.7 22.3 Mean 163 366 424

2000–2001 P0 183 335 483 334 N 5.6 16.1 P₁₅ 198 509 612 439 P 5.6 16.1 P30 208 564 642 472 N × P 9.6 27.9 Mean 197 469 579

2001–2002 P₀ 190 315 447 317 N 4.35 12.6 P₁₅ 206 482 565 418 P 4.35 12.6 P₃₀ 219 534 603 452 N × P 7.54 21.9 Mean 205 443 538

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