This is the first year of a multi-year study on the effect of compost on vegetable production. The site was double cropped this year with lettuce followed by broccoli. Compost used at 10 and 20 T/A did not affect the yield of lettuce or broccoli in this study. Compost increased the content of N, K and Ca of lettuce early in the season but not later in the season. In addition, compost increased the content of P and Zn in broccoli early in the season but had no effect later.
The study was conducted with Tonascia Farms in Hollister, CA. The soil type was a Sorrento Silty Clay Loam. Each plot was eight 40" beds wide by 50 feet long. Compost was applied with a mechanical spreader on two occasions: prior to the lettuce crop on April 3 (lilliston incorporated on 4/4) and, over the same strips, prior to the broccoli crop on July 17 (lilliston incorporated on 7/19). The compost was applied at 0, 10 and 20 T/A and there were four replications of each compost treatment. The field was sprinkler irrigated. And pest control was conducted according to the growers standard practices.
Lettuce was planted on 4/17 and watered on 4/19. It received the following fertilizer treatments: preplant (3/31)- 400 lbs 5-17-17; lst sidedress (5/23) - 400 lbs 20-00-5; 2nd sidedress (6/3) - 400 lbs 20-0-0-5. Total N applied = 180 lbs. No preplant soil N03 analysis was taken. All fertilizer was applied by tractor and was shanked into the beds. The compost strips were split into preplanted and non-preplanted and sidedressed and non-sidedressed areas. Tissue samples for nutrient analyses were gathered on 5/22; 6/5; and 6/27. Fresh sap N03 was collected from the mid-ribs of the outer wrapper leaves on 6/6; 6/19; and 6/27. Soil nitrate and ammonium levels were determined by KCI extracts on 6/2; 6/19; and 6/27. Yield data was collected from the middle 20' of row on 6/27.
Broccoli was planted on 7/24 and watered on 7/26. It received the following fertilizer treatments: 0 preplant; 1st sidedress (8/31) - 420 lbs AN 34; 2nd sidedress (9/21) - 420 lbs AN 34; Total N applied = 285 lbs. Preplant soil N03 level = 21 ppm. All fertilizer was hand applied to the plots over the top of the middle of the beds and watered into the beds. The compost strips were split into sidedressed and nonsidedressed areas. Tissue samples for nutrient analyses and fresh sap analyses were gathered on 10/1 I- 10/25 and I 1/10. A soil microbial biomass samples were sent to Elaine Ingham's lab at OSU on I 1/10 for active fungus and bacteria analyses. Yield data was collected from the middle 20' of row on I 1/1 0, I 1/1 5 and 1 1/20.
| Bulk Den. |
H2O | Ash | C | C:N | NH4 | NO3 | N | P | K | |
|---|---|---|---|---|---|---|---|---|---|---|
| lb/yd3 | ---------%-------- | ----ppm---- | --------%-------- | |||||||
| Lettuce | 1480 | 32.1 | 77.2 | 10.9 | 11.0 | 10 | 170 | 0.98 | 0.27 | 0.94 |
| Broccoli | -- | 33.8 | -- | 11.2 | 10.2 | 10 | 220 | 1.1 | -- | -- |
| pH | EC | Na | Cl | B | Zn | |
|---|---|---|---|---|---|---|
| ------------meq/L----------- | -----------ppm---------- | |||||
| Lettuce | 8.8 | 3.4 | 9.2 | 14.9 | 32 | 265 |
| Broccoli | 8.6 | --- | --- | --- | --- | |
Nutrient content of the lettuce tissue was more affected by compost and preplant applications earlier in the season. There was greater N, K and Ca in the lettuce tissue with increasing compost and less Mg at thinning (table 1). At heading and harvest compost had no effect on the amount of nutrients in the tissue (tables 2 and 3). Compost also had no effect on the fresh sap N03 levels on three sampling dates (table 4). Compost had no effect on the levels of N03 and NH4 in the soil on three sampling dates (table 5). Compost also had no effect on the yield but the preplant fertilizer contributed significantly to the yield and size of the lettuce (table 6).
Potassium was higher in the 20 T/A treatment at the first sampling date and phosphorous was lower (table 7). Magnesium was lower in the IO and 20 T/A treatments and zinc was greater on the second sampling date. Fresh sap N03 was also greater in the 20 T/A treatment (table 8). At harvest compost had no effect on nutrient content (table 9). The compost did not affect the levels of active fungi or bacteria in the soil (table 10). Compost or sidedressed fertilizer did not affected yield (table 11) probably due to residual nitrogen in the soil from the prior lettuce crop (nitrate-N prior to planting 21 ppm).